KENDRIYA VIDYALAYA SANGATHAN
KENDRIYA VIDYALAYA SANGATHAN
AHMEDABAD REGION
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FORMULAE OF CHEMISTRY AT GALANCE
Students must know at least the following formulae to solve numerical problems in chemistry specially low achiever who have fear for numerical problem. The given formulae will certainly help them out.
CLASS XII
SUBJECT : CHEMISTRY
MAIN FORMULAE
| | | | |
|SN |CHAPTER/UNIT |FORMULA |TERMS |
| | | | |
| | |1.Calculation of density: |z = no of atoms in a unit cell |
|1. |UNIT I |z. M |M = mass of unit cell |
| |SOLID STATE |d = |a = edge length |
| | |a3. NA |NA= Avagadro’s number |
| | | | |
| | |2. Edge length of hcp structure : |a = Edge length |
| | |a = 2√2.r |r = radius |
| | | | |
| | |3. Edge length of bcc structure: |a = Edge length |
| | | |r = radius |
| | |4.r | |
| | |a = √3 | |
| | | | |
| | |4. Edge length for simple cubic: |a = Edge length |
| | |a = 2.r |r = radius |
| | | | |
| | | | |
|2. |UNIT II | | |
| |SOLUTION |1. Calculation of partial vapour |p1 = vapour pressure of solution |
| | |pressure |p10 = vapour pressure of pure |
| | |p1 = p10 . xa |component. |
| | | |xa = mole fraction |
| | | | |
| | | | |
| | |Colligative properties | |
| | | | |
| | |(i) Relative lowering of |p1 = vapour pressure of solution |
| | |vapour pressure |p10 = vapour pressure of pure component co w1 = mass of|
| | |p10 - p1 = w2 . M1 |the solvent |
| | |p10 M2 .w1 |w2 = mass of the solute |
| | | |M1 = molar mass of solvent |
| | | |M2 = molar mass of solute |
| | | | |
| | | | |
| | |(ii) Elevation of boiling point |ΔTb = Increase in boiling point |
| | | |kb = Molal elevation constant |
| | |ΔTb = kb. m |m = Molarity of the solution |
| | | |w1 = mass of the solvent |
| | |kb . 1000. w2 |w2 = mass of the solute |
| | |= |M2 = molar mass of solute |
| | |M2 .w1 | |
| | | | |
| | | | |
| | |(iii)Depression of freezing point | |
| | | |ΔTf = depression of freezing point |
| | |ΔTf = kf. m |kf = Molal depression constant |
| | | |m = Molarity of the solution |
| | |Kf . 1000. w2 |w1 = mass of the solvent |
| | |= |w2 = mass of the solute |
| | |M2 .w1 |M2 = molar mass of solute |
| | | | |
| | | | |
| | |(iv) Osmotic pressure | |
| | | |Π = Osmotic pressure |
| | |Π = C.R .T |C = concentration of solution |
| | | |R = Gas constant |
| | |w2. R.T |T = Temp |
| | |= |V = Volume of the solution |
| | |M2 .V |M2 = molar mass of solute |
| | | | |
|3 |Unit III | |Ecell = emf of the cell |
| |Electrochemistry |1. Nernst Equation |E0cell = Standard emf of the cell |
| | | |R = Gas constant |
| | |Ecell = E0cell - R T ln [M] |T = Temp. |
| | |n F [Mn+] |[M] = Anodic concentration |
| | | |[Mn+] = Cathodic concentration |
| | | |n = no. of electrons in the balanced |
| | |Ecell = E0cell - 0.059 log [Anodic con] |redox reaction. |
| | |n [cathodic con] |F = Faraday constant. |
| | | | |
| | | | |
| | | |kc = Equilibrium constant |
| | |2. Relation between Equilibrium |Ecell = emf of the cell |
| | |constant and E0cell |E0cell = Standard emf of the cell |
| | | |R = Gas constant |
| | |Ecell = E0cell - 2.303 R T log kc |T = Temp. |
| | |n F |n = no. of electrons in the balanced |
| | | |redox reaction. |
| | |OR |F = Faraday constant. |
| | | | |
| | |Ecell = E0cell - 0.059 log kc | |
| | |n | |
| | | | |
| | | |k = conductivity |
| | | | |
| | |3. Molar conductivity |Λm = molar conductivity |
| | | | |
| | |Λm = k 1000 | |
| | |molarity |G* = cell constant |
| | | |l = length of the conductor |
| | |4. Cell constant |a = cross sectional area of the conductor |
| | |l | |
| | |G* = | |
| | |a |k = Rate constant |
| | | | |
| | |1st order Rate Reaction |[R]0 = Initial concentration of reactant |
| | |Equation | |
| | | |[R] = final concentration of reactant |
| | | |t = time |
|4. |UNIT IV | | |
| |Chemical kinetics |k = 2.303 log [R]0 | |
| | | | |
| | |t [R] | |
| | | | |
| | | |t1/2 = Half life time |
| | |2. Half life period | |
| | |0.693 |k = Rate constant |
| | |t1/2 = k | |
| | | | |
| | | | |
| | | |k1 And k2 are rate constants for the |
| | | |reaction at two different temp |
| | |3. Arrehenius Equation |Ea = Activation energy |
| | | |T1 & T2 are two different temp |
| | |log k2 = Ea T2 – T1 |R = Gas constant |
| | |k1 2.303R T1 T2 | |
| | | | |
| | | | |
CLASS XI
SUBJECT : CHEMISTRY
MAIN FORMULAE
| | | | |
|SN |CHAPTER/UNIT |FORMULA |TERMS |
| | |1. de Broglie’s equation |λ = Wave length |
| | |h |h= Planck’s constant |
| | |λ = |p = momentum |
| | |p | |
| | | | |
| | | | |
| | | | |
| |UNIT I | | |
|1. |STRUCTURE | | |
| |OF ATOM | | |
| | | | |
| | |2. Heisenberg’s Equation : |Δx = Change in position of particle |
| | |h |m = mass of particle |
| | |Δx.m. Δv= 4 Π |Δv = change in velocity |
| | | |h= Planck’s constant |
| | | |E = Energy of photon |
| | |3. Einstein Equation |h= Planck’s constant |
| | | |υ = Frequency of radiation |
| | |E = hυ |c = Light velocity |
| | |or E = h c /λ |λ = Wave length |
| | | | |
| | |4. Rydberg’s Equation: |υ = wave number |
| | | |n21 = Initial energy level of electron |
| | |υ = 109677 1 _ 1 cm-1|n22 = Final energy level of electron |
| | |n21 n22 | |
| | | | |
| | |1 Boyle’s Law |p = pressure of gas |
| | |p = k. 1/V |k = constant of proportionality |
| | | |v = Volume of the gas |
| | | | |
| | | | |
| | |2. Charle’s Law |V = Volume of the gas |
| | | |k = constant of proportionality |
| | |V = k.T | |
| | |Or |V1 = Initial volume of the gas |
|2. |STATES OF MATTER |V1/ V0 = T1/ T0 |Vo = Final volume of the gas |
| | | |T1 = Initial Temp of the gas |
| | | |T2 = Final Temp of the gas |
| | | | |
| | | | |
| | | | |
| | |Ideal gas equation | |
| | |PV = n RT |P = Pressure of gas |
| | | |V = Volume of the gas |
| | | |n = No. of moles of gas |
| | | |R = Gas constant |
| | |Or |T = Temp |
| | | | |
| | |P1 V2 / T1 = P2 V2/ T2 | |
| | | | |
| | | |P1 = Initial Pressure of the gas |
| | | |P2 = Final pressure of the gas |
| | | |V1 = Initial volume of the gas |
| | | |V2 = Final volume of the gas |
| | | |T1 = Initial Temp of the gas |
| | | |T2 = Final Temp of the gas |
| | | | |
| | | | |
| | | | |
| | |van der Waal’s Equation | |
| | | | |
| | |( p + an2/ v2 ) ( v - nb) = n RT |P = Pressure of gas |
| | | |V = Volume of the gas |
| | | |n = No. of moles of gas |
| | | |R = Gas constant |
| | | |T = Temp |
| | | |a & b are the van der Waal’s constant |
| | | | |
| | | | |
| | | | |
| | | | |
| | | | |
|3 |Unit VI |1. First law of thermodynamics |ΔU = Change in the internal energy |
| |Thermodynamics | |q = Heat absorbed or given out |
| | |ΔU = q + w |w = Work done |
| | | | |
| | |2. Enthalpy of system | |
| | | |ΔH = Change in enthalpy |
| | |ΔH = ΔU+ PΔV |ΔU = Change in internal energy |
| | | |P = Pressure |
| | | |ΔV = Change in volume |
| | | | |
| | | | |
| | | | |
| | |Entropy of system |ΔS = Change in entropy |
| | | |q = Heat absorbed or given out |
| | |ΔS = q / T |T = Temp |
| | | | |
| | | | |
| | | | |
| | | | |
| | | | |
| | | | |
| | |3.Change in the enthalpy of a | |
| | |reaction |F = Faraday constant. |
| | |ΔrH = Σ ( bond enthalpy of reactant) - | |
| | |Σ( bond enthalpy of products) |ΔrH = Change in the enthalpy of a reaction |
| | | | |
| | | | |
| | | | |
| | | | |
| | | | |
| | |4. Gibb’s Helmholtzs Equation |ΔG = Change in Gibb’s energy |
| | | |ΔH = Change in enthalpy |
| | |ΔG = ΔH - T ΔS |T = Temp |
| | | |ΔS = Change in entropy |
| | | | |
| | | | |
| | | | |
|4. |Unit VII |1. pH Calculation | |
| |Chemical Equilibrium | | |
| | |pH = - log [H+] |[H+] = Concentration of H+ ions |
| | | | |
| | | | |
| | |2. Relation between kw , ka & kb |kw = Dissociation constant of water |
| | | |ka = Dissociation constant of weak acid |
| | |kw = ka . kb |kb = Dissociation constant of Weak base |
| | | | |
| | | | |
| | | | |
| | |3. pH of aqueous solution of salt |Pka = - log ka |
| | |of weak acid and strong base |Pkb = - log kb |
| | | |Where |
| | |pH = 7 + ½ [Pka – Pkb] |ka = Dissociation constant of weak acid |
| | | |kb = Dissociation constant of Weak base |
| | | | |
| | | | |
| | | | |
| | | | |
| | | |Ksp = Solubility product |
| | |4. Solubility product : |[M+] = Concentration of Cations |
| | | |[X-] = Concentration of Anions |
| | |Ksp = [M+] [X-] | |
| | | | |
Thank you
CBSE QUESTION PAPER DESIGNING (PATTERN), BULE PRINT AND MARKING SCHEME
CBSE has it own and very specific way of design & pattern of question paper,blue print and marking scheme. Therefore, it is important to know about all these and to follow the same strictly, when we prapare que. Papers, Blue Print and marking scheme.
Designing of CBSE Question Paper for Chemistry :
The whole designing of question paper of chemistry of Board Exam depends on the following details, which must be told to the students very categorically.
Before I start discussion about setting and designing of question papers let me discuss about the term Learning and the points to be kept in mind while setting/designing a question paper.
1. What is learning :
According to Hilgard and Hunter
“ Learning is the process by which behaviour is organized or changed through
practice or training”
And to ensure whether learning has been successful or not there is a need of evaluation of students. And one of the best tools of evaluation is question papers. So, before we set Question papers some basics of its setting must be known. & hence lets have a glance over the point to be taken care of :
2.Points to be taken care of while framing a question paper :
Question paper must be balanced
Question paper should not be too lengthy
It must neither be very easy nor very hard
It must contain questions for all category of students i.e. weak, bright and average
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It is very clear from the above details that every aspect of the question paper is very well set and hence this must be brought to the knowledge of the students. Now second point is to discuss about blue print of question paper.
Let us know what BLUE PRINT is all about :
BLUE PRINT :
*Blue print is a frame work that gives you the focus points that the examiner has decided for the examinee at a glance.
*Blue print is schematic overview of the focus point that the examiner has to consider for evaluation of examinee.
OBJECTIVES OF BLUE PRINT
• To overview whole syllabus for the purpose of evaluation
• To make sure that total part of the syllabus is covered
• Each unit has been given due weightage
• Question paper consists of different type of questions
• To help students by letting them know about the pattern of question papers.
|Unit |VSA(1) |SA-I(2) |SA-II (2) |LA(5) |TOTAL |
|Solid State | |2(2) |- |- |2(4) |
|Solution |- |1(2) |1(3) |- |2(5) |
|Electrochemistry |- |1(2) |1(3) |- |2(5) |
|Chemical Kinetics |- |- |- |1(5)- |1(5) |
|Surface Chemistry |1(1) |- |1(3) |- |2(4) |
|General Principles& Extraction |- |- |1(3) |- |1(3) |
|p-block elements | | |-1(3) |1(5) |2(8) |
|d&f block elements |- |1(2)- |1(3) | |2(5) |
|Co-ordination compounds |1(1) |1(2) |- |- |2(3) |
|Haloalkanes& Haloarenes |- |2(2) |- |- |2(4) |
|Alcohols& Phenols |2(1) |1(2) | |- |2(4) |
|Aldehydes,Ketones& Carboxylic acids |1(1) |- |- |1(5) |2(6) |
|Organic compounds containing nitrogen |1(1) | |1(3) |- |2(4) |
|Biomolecules |1(1) |- |1(3) |- |2(4) |
|Polymers |1(1) |1(2) | |- |2(3) |
|Chemistry in everyday life |- |- |1(3) |- |1(3) |
| |8(1) |10(20) |9(27) |3(15) |30(70) |
A Blue Print for Chemistry Question Paper (Class XII )
Let us discuss about the different type of a question as mentioned in a blue print
Types of questions
← Knowledge based
← Understanding based
← Application & skill based
What are KNOWLEDGE BASED questions ?
← These questions usually starts from “how, why, what, where, whom, when, which, define, discuss, state, Name, write etc. and direct questions (eg. name reactions).
e.g. Q1. Write Kohlrausch law.
Q2. State Raoult’s law.
Q3. Define mole fraction.
What are Understanding based questions:
These include
* Reasoning Based questions
* Direct numerical
* Nomenclature
* Reaction mechanism
* To Differentiate beetween….. questions
* Derivation Based Question
*Questions starts from “to show that……”
What are Application based questions ?
These include:
* Questions based on graph
* Numerical in which application of very concepts of chemistry are involved.
* Organic conversions
* Questions which are related to our day to day life.
What are Skill based questions ?
These include
*Balancing of equation questions
*Draw structure of______ type questions
*Plot the graph of…….
*Question related to observations, practicals (eg. Smell, colour change, taste etc.
related)
From single topic different type of questions can be framed :
Q. Write Kohlrausch’s law. (If asked like this it is a knowledge based question)
Q. If molar conductivities at infinite dilution for NH4Cl,NaOH and NaCl are 129.8,217.4
and108.9 Scm2 mol-1 respectively,calculate molar conductivity at infinite dilution for
NH4OH. (If asked like this it is an understanding based question)
Q. If molar conductivities at infinite dilution for NH4Cl,NaOH and NaCl are 129.8,217.4
and108.9 Scm2 mol-1 respectively and the molar conductivity of a 10-2 M solution of
NH4OH is 9.33 Scm2 mol-1 .Calculate degree of dissociation of NH4OH in its above
mentioned solution. (If asked like this it is an Application based question as degree of
dissociation will be calculated only after calculation of molar conductivity at infinite dilution
for NH4OH )
MARKING SCHEME :
*Marking scheme of question paper is prepared to make the
evaluation procedure uniform
*Step wise marking is ensured in a marking scheme.
* All the answers must be mentioned ( in full) in the marking
Scheme. Avoid writing like and give full details of answers :
1. For correct definition- 1Mark
2. For correct reasoning - 1m
3. For correct diagram - 2m
4. For correct mechanism – 2m etc.
- Thanking you
HOW TO TAKE UP NUMERICAL PROBLEMS IN CHEMISTRY
In order to make students learn numerical problems in chemistry one must make it sure that students have been told about all the related concepts and formulae and a sufficient practice has been given in this regard, prior to solve any numerical problem. teacher must enlist all possible types of numericals of a particular unit and further sufficient practice for solution must be given, by giving different kinds question for the same formulae and concepts starting from simple and single concepts involving numerical to difficult and multiconceptual nemericals.
In this context I am to put forward such an example by taking 1st Unit of Class XII Chemistry subject (Solid State Chemistry). In which we require the following 2 tables to make student confident and comfortable to solve problems:
TABLE 1
|Sn |Type of unit cells |Edge Length (l) |Radius (r) |No. Of Sphere |Inter ionic distance |% of Packing |
| | | | |(z) | | |
|1 |Simple/Primitive |a=2r |r = a/2 |1 |= a |52.4% |
|2 |Body centred Cube/CsCl/CsBr |a=4.r/√3 |r = a√3/4 |2 |= a√3/2 |68% |
|3 |FCC/hcp/ccp/NaCl/RockSalt /ZnS |a= 4.r/√2 |r = a√2/4 |4 |= a/√2 |74% |
| |/Sphalerite/fluorite/ | | | |(Note= for Metallic solid | |
| |Antifluorite | | | |but a/2 (for ionic solids | |
| | | | | |solid) | |
Note : √2 = 1.414
√3 = 1.732
Table 2
|Radius Ratio |Coordination No. |Structural Arrangement |Structure Type |Example |
|0.155-0.225 |3 |Trigonal Planar |B2O3 |B2O3 |
|0.225-0.414 |4 |Tetrahedral |ZnS /Sphalerite |ZnS,CuCl,HgS,CuBr etc. |
|0.424-0.732 |6 |Octahedral |NaCl/RockSalt |NaCl, MgO, CaO etc. |
|0.732-1.00 |8 |Cubic |CsCl type |CsCl, TlBr, NH4Br etc. |
Now, on the basis of the above table it is very easy for the students to find
formulae/required data to solve any kind of problems.
Now let us have glance over all possible kind of numericals in the unit and give sufficient practice to each student for each of the following possible types of numericals:
1. To calculate density : Use the following formula -
z. M
d =
a3. NA
2. To calculate Cell dimensions (l, a, r, inter-ionic distance etc.) :
Use the above formula according to need and see the table 1
to find out inter-ionic distance.
3. To calculate Molar mass or Molecular mass or Atomic mass etc :
Use above equation given in the 1st point. (Note that molar mass
must be reported in g/mol
4. To find NA or Number of particles/spheres/Atoms/ions/molecule etc.:
Use above equation given in the 1st point.
5. To find fractions of ions in the given formula of oxides or other
molecule: For such question use the oxidation concept taught in XI chemistry.
6. To Predict Molecular Formula of the given constituent
particles/spheres/Atoms/ions:
Use the following conceptual point to solve such problem
7. Doping Related problems : (see the problem related with doping of NaCl with
SrCl2)
8. To find coordination no. of the given sphere.(Use table 2)
9. To predict nature of the unit cell on the basis of z (Use table no.1)
10. To find Radius Ratio on the basis of Co-ordination no. (Use table 2)
11. To find the range of the cation/anion on the basis of radius ration.
(Use table 2)
12. To find the nature of the unit cell on the basis of Radius ratio.
(Use table 2)
- Thank You
UNIT WISE DIFFICULT AREAS MENTIONED BY PARTICIPANTS
THE SOLID STATE
1. 3-D Representation of solids
2. Numericals/calculations
3. Magnetic properties
4. Defects of solids
SOLUTIONS
1. Numericals on Vant hoff factor
2. Ideal&Non-ideal solutions
ELECTROCMEMISTRY
1. Nerst equation
CHEMICAL KINETICS
1. Fractional order of reaction
2. Log table
3. Numericals based on initial rate&activation energy
SURFACE CHEMISTRY
1. Preferential adsorption of ions.
2. Charge on colloids.
GENERAL PRINCIPLES OF EXTRACTION &ISOLATION OF ELEMENTS
Ellingham Diagram
p-BLOCK ELEMENTS
Difficulty faced by exception cases
d&f BLOCK ELEMENTS
Electrode potential of transition elements
M.Pt of transition elements
Cu+/Cu+2 Stability
COORDINATION CHEMISTRY
1.Valence bond theory
2.Crystal field theory
ORGANIC CHEMISTRY(Unit 10-13)
Basicity of amines ,
Note : All the above topic were discussed and solved by The Course Director and Resource Persons
UNIT WISE IMPORTANT TOPICS COMPILED BY THE PARTICIPANTS
UNIT-1 Marks-4
Solid state
Group terms and Definitions:-
• Anisotropy: - Property like refractive index, X-ray diffraction etc. are different through different axis. This property shown by crystalline solid.
• Classification of crystalline solids:-
|Types of solid |Force of attraction |Milting point |Examples |
|Atomic or molecular |Vander waal force, Hydrogen |Very less |Dry ice, Solid NH3 etc. |
| |bonding etc. | | |
|Covalent network solid |Covalent force |Very high |Quartz,Diamand. |
|Ionic solid |Ionic force |Very high |NaCl, KF |
|Matallic solid |Metallic force |High |Fe,Sn,Alloys etc. |
• Unit cell and cell dimension.
|Unit cell |Edge length |Coordination no. |% occupied space |% free space |
|Simple cubic cell |a=2r |06 |52 |48 |
|B.C.C |a=4r/√3 |08 |68 |32 |
|F.C.C/HCC/CCP |a=4r/√2 |12 |72 |28 |
• F- Centre: - It is the defect in which when an alkali metal halide is heated in the vapour of alkali metal the excess cation occupy the crystal lattice and anion vacancy filled with the valance electron. So that the crystal appear coloured.
• P-type semiconductor: - The semiconductor formed by doping of elements of less valence electron with crystal. For example Si (VE=4) dopped with Ga(VE=3)
• n – type semiconductor :- The semiconductor formed by dopping of element with a crystal. For example Si (VE=4) dopped with As (VE=5).
Photovoltaic Material: The material which converts sun light into electricity is called photo voltaic material.
[ Amorphous silica ]
Crystalline solid
[1] In a crystalline solid the particles (atoms, molecules or ions) are arranged in a regular and repetitive
three dimensional arrangements
[2] These solids have sharp melting point.
[3] These solids are anisotropic, i.e. their physical properties such as electrical conductivity, refractive
index, thermal expansion etc. have different values in different directions.
[4] These solids can under go a clean cleavage.
[5] These solids are generally incompressible.
Examples: All the metallic elements like iron, copper and silver;
Non – metallic elements like sulphur, phosphorus and iodine and
Compounds like sodium chloride, zinc sulphide and naphthalene
Amorphous solid
[1] In amorphous solid the particles (atoms, molecules or ions) are arranged in an irregular and
non repetitive three dimensional arrangements.
[2] Rapidly solidified liquids are amorphous substances, e.g. Glass, rubber etc.
[3] These solids are generally isotropic, i.e. physical properties are same in all directions.
[4] These solids on cleavage form smaller pieces with non-planar faces.
[5] These solids do not have sharp melting point and boiling point i.e. they melt gradually over a
temperature range.
[6] These solids are compressible.
What makes a glass different from a solid such as Quartz? Under what conditions quartz could be converted into glass?
In glass, amorphous silica ( SiO2 ) is present. SiO4 tetrahedral have an irregular arrangement.
In quartz, crystalline silica ( SiO2 ) is present. SiO4 tetrahedral have a regular arrangement.
When quartz (SiO2 ) is melted and the melt is cooled very rapidly, quartz converted into glass.
Fluid
Liquids and gases are called fluids because of their ability to flow. The fluidity is due to the fact that the molecules are free to move about.
Why glass pans fixed to windows or doors of old building are invariably found to be slightly thicker at the bottom than at the top?
Due to fluidity property, the glasses flows down very slowly and make the bottom portion slightly thicker.
Why solids are rigid in nature?
The constituent particles in solid have fixed position and can only oscillate about their mean position, for which solids are rigid.
Name the factors which determine the stability of a substance.
[1] Intermolecular forces tend to keep the molecules or constituent particles closer.
[2] Thermal energy tends to keep them apart by making them move faster.
Characteristic properties of solid
[1] They have definite mass, volume and shape.
[2] The inter molecular distances are short.
[3] The inter molecular forces are strong.
[4] Their constituent particles have fixed positions and can only oscillate about their mean positions.
[5] They are incompressible and rigid.
Why glass is considered as a super cooled liquid?
Amorphous solids have a tendency to flow. Since glass is an amorphous solid , so it is called super cooled liquid or pseudo solid.
Why some glass objects from ancient civilizations are found to become milky in appearance?
Glass becomes crystalline at some temperature. For which glass objects from ancient civilizations become milky in appearance because of some crystallization.
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Space lattice or crystal lattice
A regular three dimensional arrangement of points in space is called space lattice or crystal lattice. The points represent the constituent particles of the crystal.
Unit cell
An unit cell is the smallest portion of the crystal lattice. When it is moved repeatedly a distance equal to its own dimension along each direction, a three dimensional crystal lattice is generated.
Types of unit cell
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[2] Non-Primitive unit cell / centered unit cell- In this type of unit cells, particles as points are present not
only at the corners but also at some other positions.
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Packing in metallic crystal:-
The identical solid spheres can be packed in a number of ways.
[1] In the first layer the spheres are arranged in a hexagonal manner in which each sphere is in contact
with six other spheres.
[2] In the second layer the spheres will fit into the depression of the first layer.
[3] For the third layer, there are two possibilities:-
(a) The spheres can be placed in the depression of the second layer i.e. the third layer is directly above
the first and the fourth layer is directly above the second. This leads to the arrangement ABABAB……
This type of arrangement is known as hexagonal closed packed (HCP) structure.
e.g. Zinc, magnesium crystallizes in this type of structure.
[b] Alternatively, the sphere can be placed in the depressions, of the second layer; do not lie directly
above the atoms of the first layer i.e. the spheres in fourth layer lie exactly above the first, fifth above
the second, sixth above the third and so on. This leads to the arrangement ABCABCABC……….
This type of arrangement is cubic closed packed or face centered cubic arrangement.
e.g. Cu,Ag.Au crystallizes in this type of structure.
Co-ordination number
It is the number of atoms or spheres that surrounds the single sphere / atom in a crystal.
C.Nof tetragonal arrangement = 3
C.Nof tetrahedral arrangement = 4
C.Nof octahedral arrangement = 6
C.Nof body centered cubic arrangement = 8
Any close ( tight ) packing having C.N = 12 i.e. hcp and ccp i.e. fcc having C.N = 12
Void / Hole/ Interstices
The space which is left in between the closest pack arrangement is called void. In close packing two types of voids are created.
[pic]
Relationship between edge length (a) and radius of the sphere ( r ) in unit cell.
[pic]
[pic]
Gold(At.radius= 0.144nm)crystallizes in aFCC unit cell. What is the length of the side oftheunitcell?
Atomic radius= 0.144 nm
So, length of side a = 2 √ 2 r = 2 √ 2 x 0.144 = 0.406 nm
Aluminum crystallizes in a cubic closed packed structure. Its metallic radius is 125 pm.
[1] What is the length of the side of the unit cell ?
[2] How many unit cells are there in one c.c of aluminium?
[1] For FCC , a = 2 √ 2 r = 2 √ 2 x 125 = 354 pm, So the edge length of the unit cell = 354 x 10 -10 cm
[2] Volume of unit cell = a3 = ( 354 x 10 -10 ) 3 cm 3
Therefore, number of unit cells in 1 cc of aluminum = 1/ ( 354 x 10 -10 ) 3 cm 3 = 2.254 x 10 22 Unit cells
[pic]
[pic]Ferric oxide crystallizes in a hexagonal closed pack array of oxide ions with two out of every three octahedral holes occupied by ferric ions. Deduce the formula of the ferric oxide.
No. of atoms in one unit cell of hcp structure = 6 No. of oxide ions per unit cell = 6
No. of octahedral voids = 6
Since ferric ions occupy only two out of every three octahedral voids, there fore, no. of octahedral voids occupied by ferric ions = ( 2/3 ) x 6 = 4 Stoichiometric ratio of Fe 3+ and O 2- is 4 : 6 = 2 : 3
Hence the formula of ferric oxide is Fe2O3
Analysis shows that nickel oxide has the formula Ni 0.98 O 1.00. What fraction of nickel exist as Ni 2+ and Ni3+ ions?
Let amount of Ni3+ be x mol. Then amount of Ni2+ is (0.98 – x)
Total oxidation number of Ni in the compound is 3x + 2 (0.98 – x)
Oxidation number of oxygen is -2
Since the sum of the oxidation number of all the constituents in a compound is zero.
=> 3x + 2 (0.98 – x) – 2 = 0 => 3x + 1.96 – 2x – 2 = 0 => x = 0.04
Hence % of Ni3+ = ( 0.04 / 0.98 ) x 100 = 4.08 % % of Ni2+ = 100 – 4.08 = 95.92 %
Relationship between density (d) and the dimension of unit cells.
Let the edge length of unit cell be a There fore volume of unit cell = a 3
Let no. of atoms in unit cell = Z Gm. Atomic mass = M
There fore mass of one atom = M / NA Where NA = Avogadro’s number i.e. 6.023 x 1023
[pic]
Silver crystallizes in FCC lattice. If edge length of the cell is 4.05 x 10 – 8 cm and density is
10.5 gm/cm3 . Calculate atomic mass of silver.
Given data-
Edge length ( a ) = 4.07 X 10 – 8 cm Density ( d ) = 10.5 gm/ cm3
Since silver crystallizes in fcc lattice, so rank , i.e. the no. of silver atoms per unit cell ( z ) = 4
NA = 6.023 X 10 23
[pic]
[pic]
[pic]
# Single crystals are formed when the process of crystallization occurs at extremely slow rate.
# Point defects are the irregularities or deviations from ideal arrangement around a point or an atom in a
crystalline substance.
# Line defects are the irregularities or deviations from ideal arrangement in entire rows of lattice points.
# Point defects do not disturb the stoichiometric of the solid is known as stoichiometric defect or intrinsic
defect or thermodynamic defect.
# Vacancy defect – When some of the lattice sides are vacant, the crystal is said to have vacancy defect.
This results the decrease in density of the substance. This defect develops when a substance is heated.
# Interstitial defect- When some constituent particles occupy an interstitial site, the crystal is said to
have interstitial defect. This defect increases the density of the substance.
Schottky defect
[1] It occurs when a pair of ions of opposite charge are missing from the ideal lattice.
[2] The presence of a large number of Schottky defect in a crystal lowers its density.
[3] This defect occurs if cation and anion having similar size with high coordination number.
[4] In sodium chloride, there is one schottky defect for 1016 ions. One c.c of sodium chloride contains 1022
ions. Therefore, one cc of sodium chloride possesses 106 schottky pair of ions.
Frenkel defect
[1] When an ion leaves its position in the lattice and occupy interstitial site leaving a gap in the crystal i.e.
it creates a vacancy defect and interstitial defect.
[2] This defect will occur if size of cation is smaller than anion, with low coordination number.
[3] Frenkel defects are not found in pure alkali halide. Due to larger size of cations, ions can not accommodate in interstitial site.
[4] Frenkel defect are found silver halide, because silver ions are smaller in size and can get into the interstitial site.
[5] The Frenkel defect does not change the density of the solid.
[6] In silver bromide, both Schottky and Frenkel defects are found.
Metal excess defect
[a] F-Centers ( Farbe: means colour )
[1] When there is an excess of metal ions in non-stoichiometric compounds, the crystal lattice has vacant
anion site. The anion sites occupied by electrons are called F-centre.
[2] The F-centers are associated with the colour of the compounds. Excess of K in KCl makes the crystal
violet. Excess of Li in LiCl makes the crystal pink.
[3] Solid containing F-centre are paramagnetic, because the electrons occupying the F-centers are
unpaired.
[4] When the crystal having F-centers are exposed to light, they become photoconductor.
[b] Metal excess defect due to presence of extra cation at the interstitial site
Zinc oxide is white in colour at room temperature on heating, it looses oxygen and turns yellow.
[pic]Now there is excess of zinc in the crystal and its formula becomes Zn 1+ x O
The excess zinc ions move to interstitial site and the electrons to neighboring interstitial site.
Metal deficiency defect
FeO, mostly found with a composition of Fe 0.95 O i.e. range from Fe0.93O – Fe0.96O. In crystals of FeO, some Fe2+ ions are missing and the loss of positive charge is made up by the presence of required number of Fe3+ ions.
Electron sea model of metallic bonding
[1] A metal consists of a lattice of positive ions ( Kernel ) immersed in a sea of valence electrons ( mobile
electrons )
[2] The force of attraction between the mobile electrons and the the kernels is known as metallic bond.
[3] The electrical and thermal conductivity of metals can be explained by the presence of mobile electrons
in metal.
The Band Model Of Metallic Bonding
The band model of metal is based on molecular orbital theory.
When a large no. of orbital overlap in metal, it results a continuous energy level produced by a large number of molecular orbital is called energy band.[pic]
Impurity defect ( Doping )
The introduction of defects in a particular crystalline solid by the addition of other elements is known as doping.
Doping increases the conductivity of crystal. For example, if we mix strontium chloride ( SrCl2 ) with sodium chloride, some strontium ( Sr2+ ) ions occupy the lattice sites of sodium ions ( Na +) and equal number of sodium ( Na+ ) sites remain vacant. Such vacancies in the crystal increase the electrical conductivity because certain ions from the neighboring sites can move into these vacant holes. In this defect the number of positive ions are less as compared to negative ions. Crystals with such defects also act as semiconductor. Since the conductivity is due to holes, these are known as P-type semiconductors.
If NaCl is doped with 10-3 mol % of SrCl2. What is the concentration of cation vacancies?
The addition of SrCl2 to NaCl produces cation vacancies equal in number to that of Sr2+ ions.
No. of moles of SrCl2 added to one mol of NaCl = 10-3 / 100 = 10-5 mol.
No. of holes created in one mole of NaCl = 10-5 X 6.023 X 1023 = 6.023 x 1018
Semiconductor
These are solids whose conductivity lies in between those of conductors and insulators. The conductivity of semiconductors increases with increase of temperature.
Intrinsic semiconductor
An insulator capable of conducting electric current at higher temperature or when irradiated with electromagnetic radiations, are known as intrinsic semiconductor.
This happens because certain covalent bonds are broken and the released electrons are in a position to conduct electric current. e.g. Silicon , Germanium.
Extrinsic semiconductor
These are formed when impurities of certain elements are added (doped) to insulator.
N-type semiconductors
It is obtained by doping group – 14 elements with group – 15 elements.
Suppose Si is doped with P with 5 valence electrons, out of 5 valence electrons, only 4 valence electrons are involved in bond formation.
The fifth electron is not bound any where and can be easily promoted to the conduction band. The conduction is thus mainly caused by the movement of electrons.
P-type semiconductors
It is obtained by doping group – 14 elements with group – 13 elements.
Suppose Si is doped with Ga which has 3 valence electrons, 3 valence electrons are involved in bond formation with neighboring Si atom.
A vacancy is left which can be filled by the transfer of a valence electron from a neighboring Si atom.
The movement of electron into the vacancy leaves behind a hole which carries positive charge.
Another electron from a neighboring Si atom can move into the hole leaving behind another hole. It appears as if the hole has moved through the lattice.
The movement of positively charged hole is responsible for the conduction of charge.
Non-stoichiometric cuprous oxide, Cu2O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1. Can you account for the fact that this substance is a p-type semiconductor?
[1] Since Cu2O is non-stoichiometric oxide, it contains Cu in two oxidation states, +1 and +2.
[2] Cu2+ provides an excess of positive charge. As a result an electron from a neighboring Cu+ is transferred
to Cu2+.
[3] The transfer of electron leaves behind a hole, which carries an extra positive charge and a negative hole
is created.
[4] It appears that the positive hole moves through the lattice, hence it appears as P-type semiconductor.
12 – 16 and 13 – 15 compounds
Combination of elements of Gr – 13 and Gr – 15 or Gr – 12 and Gr – 16 produce compounds which stimulate average valence of four as in Ge or Si .
12 – 16 compounds –> ZnS, CdS, CdSe, HgTe
13 – 15 compounds –> InSn, AlP, GaAs
Magnetic properties
[1] Diamagnetic
Diamagnetic substances are the substances which are weakly repelled by a magnetic field.
The electrons in diamagnetic substances are all paired. They do not contain unpaired electrons.
e.g. TiO2 , NaCl , C6H6 ,N2 , Zn
[2] Paramagnetic
Paramagnetic substances are those which are attracted by a magnetic field but they lose their
magnetism in the absence of magnetic field.
These substances have permanent magnetic dipole, due to presence of atoms, molecules or ions
containing unpaired electrons.
e.g. Cu2+, Fe3+, O2 , NO, CuO, etc.
Substances containing unpaired electrons are further classified as:
a) Ferromagnetic substances –> Ferromagnetic substances are those substances which are strongly attracted by a magnetic field and can be made into permanent magnets.
These substances show magnetism even in the absence of a magnetic field.
The large magnetism in these substances is due to the spontaneous alignment
of magnetic moment,i.e Unpaired electron in the same direction.
Example: Iron, cobalt, nickel, gadolinium and CrO2
CrO2 is used to make magnetic tapes for audio recording.
b) Anti-ferromagnetic substances –> Anti-ferromagnetic substances
are those substances in which equal number of magnetic moments
are aligned in opposite directions so as to give zero net moment.
Example: MnO, MnO2 and Mn2O3
c) Ferrimagnetic substances
Ferrimagnetism is observed when the magnetic moments
of the domains in the substance are aligned in parallel and
anti-parallel directions in unequal numbers They are weakly
attracted by magnetic field as compared to ferromagnetic substances.
Example: Fe3O4 (magnetite) and ferrites like MgFe2O4 and ZnFe2O4
These substances also lose ferrimagnetism on heating a
|TERMS |EXPLANATIONS |
|Amorphous and Crystalline Solids |Amorphous- short range order, Irregular shape eg-glass |
| |Crystalline Solids- long range order, regular shape eg : NaCl |
|Molecular solids |Ar, CCl4, H2O (ice) |
|Covalent or Network solid |SiO2 diamond |
|No of lattice points per unit cell |Simple cubic -4, BCC- 9, FCC – 14 , End-Centred- 10 |
|No of atoms per unit cell (z ) |Simple cubic -1, BCC- 2, FCC – 4 , End-Centred- 2 |
|Coordination Number |FCC- 6:6 BCC- 8:8 |
|Calculation of number of voids |Let the number of close packed spheres be N, then: |
| |The number of octahedral voids generated = N |
| |The number of tetrahedral voids generated = 2N |
|Relation between r and a |Simple Cubic( a = 2r , BCC( 4r = a√3 FCC( 4r = a√2 |
|Packing Efficiency |Simple Cubic(52.4% , BCC( 68% , FCC( 74% |
|Calculations Involving Unit Cell | |
|Dimensions |[pic] M=molar mass (g/mol) a = edge length in cm , |
| |NA = 6.023× 1023 |
|Frenkel Defect: |Ccation is dislocated to an interstitial site. It does not change the density of the solid.|
| |Frenkel defect is shown by ionic substance in which there is a large difference in the size|
| |of ions, for example, ZnS, AgCl, AgBr and AgI due to small size of Zn2+ and Ag+ ions. |
|Schottky Defect |A vacancy defect. The number of missing cations and anions are equal. Density decreases. |
| |For example, NaCl, KCl, CsCl and AgBr. |
|Metal excess defect due to anionic vacancies |When NaCl heated in an atmosphere of Na vapour, the Na atoms deposited on the surface of |
|(F-centres ) |the crystal. The Cl– ions diffuse to the surface of the crystal and combine with Na atoms |
| |to give NaCl. The |
| |released electrons diffuse into the crystal and occupy anionic sites The anionic sites |
| |occupied by unpaired electrons are called F-centres They impart yellow colour to the |
| |crystals of NaCl. Similarly, excess of lithium makes LiCl crystals pink and excess of |
| |potassium |
| |makes KCl crystals violet (or lilac). |
|Doping |The conductivity of intrinsic semiconductors is increased by adding an appropriate amount |
| |of suitable impurity. This process is called doping |
| n / p -type semiconductors |n- type : Si + As or Sb or Bi p-type: Si + B or Ga or In or Tl |
|13 –15 compounds &12–16 compounds |13 – 15 compounds: InSb, AlP and GaAs. |
| |12 – 16 compounds :ZnS, CdS, CdSe and HgTe |
|Paramagnetic substances |Weakly attracted by a magnetic field. Examples: O2, Cu2+, Fe3+, Cr3+ |
|Diamagnetic substances |Weakly repelled by a magnetic field. Example: H2O, NaCl and C6H6 |
|Ferromagnetism: |A few substances like iron, cobalt, nickel, gadolinium and CrO2 are attracted very strongly|
| |by a magnetic field. |
|Antiferromagnetism |MnO. Domains oppositely oriented and cancel out magnetic moment |
|Ferrimagnetism: |domains aligned in parallel and anti-parallel directions in unequal numbers . Example: |
| |Fe3O4 (magnetite) |
Impurity defect ( Doping )
The introduction of defects in a particular crystalline solid by the addition of other elements is known as doping.
Doping increases the conductivity of crystal. For example, if we mix strontium chloride ( SrCl2 ) with sodium chloride, some strontium ( Sr2+ ) ions occupy the lattice sites of sodium ions ( Na +) and equal number of sodium ( Na+ ) sites remain vacant. Such vacancies in the crystal increase the electrical conductivity because certain ions from the neighboring sites can move into these vacant holes. In this defect the number of positive ions are less as compared to negative ions. Crystals with such defects also act as semiconductor. Since the conductivity is due to holes, these are known as P-type semiconductors.
If NaCl is doped with 10-3 mol % of SrCl2. What is the concentration of cation vacancies?
The addition of SrCl2 to NaCl produces cation vacancies equal in number to that of Sr2+ ions.
No. of moles of SrCl2 added to one mol of NaCl = 10-3 / 100 = 10-5 mol.
No. of holes created in one mole of NaCl = 10-5 X 6.023 X 1023 = 6.023 x 1018
Semiconductor
These are solids whose conductivity lies in between those of conductors and insulators. The conductivity of semiconductors increases with increase of temperature.
Intrinsic semiconductor
An insulator capable of conducting electric current at higher temperature or when irradiated with electromagnetic radiations, are known as intrinsic semiconductor.
This happens because certain covalent bonds are broken and the released electrons are in a position to conduct electric current. e.g. Silicon , Germanium.
Extrinsic semiconductor
These are formed when impurities of certain elements are added (doped) to insulator.
N-type semiconductors
It is obtained by doping group – 14 elements with group – 15 elements.
Suppose Si is doped with P with 5 valence electrons, out of 5 valence electrons, only 4 valence electrons are involved in bond formation.
The fifth electron is not bound any where and can be easily promoted to the conduction band. The conduction is thus mainly caused by the movement of electrons.
P-type semiconductors
It is obtained by doping group – 14 elements with group – 13 elements.
Suppose Si is doped with Ga which has 3 valence electrons, 3 valence electrons are involved in bond formation with neighboring Si atom.
A vacancy is left which can be filled by the transfer of a valence electron from a neighboring Si atom.
The movement of electron into the vacancy leaves behind a hole which carries positive charge.
Another electron from a neighboring Si atom can move into the hole leaving behind another hole. It appears as if the hole has moved through the lattice.
The movement of positively charged hole is responsible for the conduction of charge.
Non-stoichiometric cuprous oxide, Cu2O can be prepared in laboratory. In this oxide, copper to oxygen ratio is slightly less than 2:1. Can you account for the fact that this substance is a p-type semiconductor?
[1] Since Cu2O is non-stoichiometric oxide, it contains Cu in two oxidation states, +1 and +2.
[2] Cu2+ provides an excess of positive charge. As a result an electron from a neighboring Cu+ is transferred
to Cu2+.
[3] The transfer of electron leaves behind a hole, which carries an extra positive charge and a negative hole
is created.
[4] It appears that the positive hole moves through the lattice, hence it appears as P-type semiconductor.
12 – 16 and 13 – 15 compounds
Combination of elements of Gr – 13 and Gr – 15 or Gr – 12 and Gr – 16 produce compounds which stimulate average valence of four as in Ge or Si .
12 – 16 compounds –> ZnS, CdS, CdSe, HgTe
13 – 15 compounds –> InSn, AlP, GaAs
Magnetic properties
[1] Diamagnetic
Diamagnetic substances are the substances which are weakly repelled by a magnetic field.
The electrons in diamagnetic substances are all paired. They do not contain unpaired electrons.
e.g. TiO2 , NaCl , C6H6 ,N2 , Zn
[2] Paramagnetic
Paramagnetic substances are those which are attracted by a magnetic field but they lose their
magnetism in the absence of magnetic field.
These substances have permanent magnetic dipole, due to presence of atoms, molecules or ions
containing unpaired electrons.
e.g. Cu2+, Fe3+, O2 , NO, CuO, etc.
Substances containing unpaired electrons are further classified as:
d) Ferromagnetic substances –> Ferromagnetic substances are those substances which are strongly attracted by a magnetic field and can be made into permanent magnets.
These substances show magnetism even in the absence of a magnetic field.
The large magnetism in these substances is due to the spontaneous alignment
of magnetic moment,i.e Unpaired electron in the same direction.
Example: Iron, cobalt, nickel, gadolinium and CrO2
CrO2 is used to make magnetic tapes for audio recording.
e) Anti-ferromagnetic substances –> Anti-ferromagnetic substances
are those substances in which equal number of magnetic moments
are aligned in opposite directions so as to give zero net moment.
Example: MnO, MnO2 and Mn2O3
f) Ferrimagnetic substances
Ferrimagnetism is observed when the magnetic moments
of the domains in the substance are aligned in parallel and
anti-parallel directions in unequal numbers They are weakly
attracted by magnetic field as compared to ferromagnetic substances.
Example: Fe3O4 (magnetite) and ferrites like MgFe2O4 and ZnFe2O4
These substances also lose ferrimagnetism on heating and become paramagnetic.
|(important questions with answer) |
•
Q.1) What are the stoichiometric defects found in ionic crystals? (1 Mark)
(Ans) The point defects in which the ratio of cations to anions remains the same as shown by the molecular formula of the compound are known as stoichiometric defects.
Q.2) Write two examples of amorphous solids. (1 Mark)
(Ans) Rubber and quartz glass are examples of amorphous solids.
(Q.3) Name two metals which have cubic closepacked structure. (1 Mark)
(Ans) Silver (Ag) and copper (Cu) have cubic close packed structure.
(Q.4) Name the type of solids which are malleable, ductile and electrical conductors. (1 Mark)
(Ans) Metallic solids are malleable, ductile and electrical conductors.
(Q.56) Sometimes,crystals of common salt (NaCl) are yellow instead of being pure white. Why?(1 Mark)
(Ans) Sometimes,crystals of common salt (NaCl)are yellow instead of being pure white due to the presence of electrons in some lattice sites in place of anions.These sites actas F-centers and impart yellow colour to crystal of common salt.
(Q.6) What are voids? (1 Mark)
(Ans) Voids are the empty spaces present between atoms or ions, when they are packed within the crystal.
(Q.7) How many atoms are present in the unit cell of bcc and fcc? (1 Mark)
(Ans) Number of atoms in unit cell of bcc is2and infcc it is 4.
(Q.8) Fe3O4 is ferrimagnetic at room temperature. What happens to its magnetic properties when it is heated to 850 K? (1 Mark)
(Ans) When Fe3O4 is heated to 850 K it loses ferrimagnetism and becomes paramagnetic.
(Q.9) Name the point defect which lowers the density of a crystal. (1 Mark)
(Ans) Schottky defect lowers the density of a crystal.
(Q.10) Write the unit in which the magnitude of magnetic moment is measured. (1 Mark)
(Ans) The magnetic moment is measured in Bohr magneton ([pic]B).
(Q.11) What do you mean by F-center? (1 Mark)
(Ans) Theanionsites which are cccupied by unpairedelectron are called F-centres.
Q.(12) Name the type of solids which have long range orders. (1 Mark)
(Ans) crystalline solids have long range order.
(Q.13) Name one solid which has both Frenkel and Schottky defects? (1 Mark)
(Ans) Silver bromide (AgBr) has both Schottky and Frenkel defects.
(Q.14) Why is the window glass of the old building thick at the bottom?
(1 Mark)
(Ans) Glass is a pseudo solid, that is, it is a supercooled liquid of high viscosity. It flows down very slowly and makes the bottom portion of window glass of old building slightly thicker.
(Q.15) What causes the conduction of electricity by semiconductors? (1 Mark)
(Ans) Electrons and holes produced by defects cause the conduction of electricity by semiconductors.
(Q.16) Name the salt which can be added to AgCl so as to produce cationic vacancies. (1 Mark)
(Ans) SrCl2orCdCl2 is added to AgCl to produce cationic vacancies.
(Q.17) What is a diode? (1 Mark)
(Ans) Diode is a combination of n- type and p- type semiconductors. It is used as a rectifier.
(Q.18) Name a transition metal oxide which has appreance and conductivity like that of Cu? (1 Mark)
(Ans) Rhenium oxide (ReO3)
(Q.19) What is the co-ordination number of an atom present in octahedral void?
(1 Mark)
(Ans) The co-ordination number of atom present in octahedral void is 6.
(Q.20) Write one property which is caused due to the presence of F-center in a solid. (1 Mark)
(Ans) The colours and paramagnetic behaviour of the solid is due to the presence of F-center in a solid.
(Q.21) Draw body centred and face centred cubic unit cells. (2 Marks)
(Ans)[pic](Q.22) Define: (i) Crystal lattice (ii) Packing efficiency (2 Marks)
(Ans) (i)Crystal lattice is the well-defined regular arrangement of atoms, molecules or ions in three-dimensional space.
(ii) Packing efficiency is the percentage of the total space filled by the particles.
(Q.23) Explain the following with suitable example:
(i) Molecular solids (ii) Metallic solids (2 Marks)
(Ans) (i) In molecular solids, the constituents particles are molecules which areheld together by van der Waals forces of attraction. E.g. I2.
(ii)Metallic solids consist of positive ions surrounded by andheld together bya sea of free electrons. These free electrons are mobile and are responsible for high thermal and electrical conductivity of metallic solids. E.g. Ag, Cu.
(Q.24) What is rank? Find rank of face centered cubic unit cell. (2 Marks)
(Ans) Rank is the number of atoms per unit cell of a crystal.
In f c c Contribution of atoms present at the corners= [pic]
Contribution of atoms present at faces = [pic]
[pic]Rank = 1 + 3 = 4.
(Q.25) What is doping? How does n-type and p-type semiconductors formed? (2 Marks)
(Ans) The process of introducing atoms of other elements as impurity into an insulator to make it semiconductor is called doping. Doping of silicon or germanium with electron rich impurities like P, As, Sb results in formation of n-type semiconductors whereas p-type semiconductors are formed by adding elements of group 13 like B, Al,Ga.
(Q.26) Explain the following with one example each:
(i)Ferrimagnetism (ii)Antiferromagnetic substances (2 Marks)
(Ans) (i) When magnetic moments are aligned in parallel and anti parallel directions in unequal numbers itresults in net moment. It is called ferrimagnetism. These substances are weakly attracted by magnetic field as compared to ferromagnetic substances.E.g:Magnetite (Fe3O4)
(ii) Antiferromagnetic substances are expected to posses paramagnetism or ferromagnetism but actually they possess zero net magnetic moment. It is due to the presence of equal number of domains in opposite direction. E.g: MnO.
(Q.27) Write two differences between isotropy and anisotropy. (2 Marks)
(Ans)
|Isotropy |Anisotropy |
|(i)These substances show identical values of physical properties |These substances show different values of physical properties in |
|in all directions. |different directions. |
|(ii) Amorphous solids show isotropy. |Crystalline solids show anisotropy. |
(Q.28) Potassium metal crystallizes in bcc. The edge length of unit cell is 4.3 A0. Find the radius of potassium atom. (2 Marks)
(Ans)
[pic]
(Q.29) A solid is made of two elements A and B. Atoms of element A ocupy all the tetrahedral sites while atoms of element B are in ccp arrangement.From this data find the formula of the compound. (2 Marks)
(Ans) There are 2 tetrahedral sites per atom of B because atoms of element B have ccp arrangement.There are 2 atoms of element A for each atom of element B because all tetrahedral sites are occupied by atoms of element A. Therefore, the formula of the compound is A2B.
(Q.30) A solid A+ B– has NaCl closed packed structure. The radius of anion is 245 pm. Find radius of anion. (2 Marks)
(Ans) The co-ordination number of A+ B– = 6 ( [pic]It has NaCl type structure.)
For this, [pic]
[pic][pic]
(Q.31) The edge length of unit cell of NaCl crystal lattice is 5.6A0. The density of NaCl is 2.2g cm–3. Find the number of formula units of NaCl per unit cell. (2 Marks)
(Ans)
[pic]
(Q.32) Find the number of NaCl molecules in a unit cell of its crystal. (2 Marks)
(Ans)
[pic]
[pic]No. ofNaCl molecules in aunit cellof NaCl= 4
(Q.33) A compound is made of two atoms X and Y. Atom X is arranged in ccp and atom Y occupies tetrahedral site. Find the formula of compound.(2 Marks)
(Ans) No. of atoms of X = 8
No. of atoms of Y =(8/8 ) + (6/2) = 4
[pic]Ratio of X : Y is 2: 1
[pic]Formula of compound is X2Y.
(Q.34) The unit cell of metallic silver is face-centred cubic. What is the mass of a silver unit cell? (Ans) (2Marks)
[pic]
(Q.35) A metal crystallizes as face centered cubic lattice with edge length of 450pm. Molar mass of metal is 50g mol–1. Find the density of metal.(2 Marks)
(Ans)
[pic]
(Q.36) A solid has bcc structure. Distance of closest approach between two atoms is 1.73A0. Find edge length of cell. (2 Marks)
(Ans) In bcc, distance of closest approach =[([pic]3)/2] edge length
[pic]
Or Edge length =[1.73/[pic]3][pic]2A[pic]
= 200pm
(Q.37) Classify the following solids as metallic; molecular,amorphous, covalent or ionic.
(i) SO2 (ii) Diamond (iii) I2 (iv) MgO
(iv) Ag (v) Quartz (vi) Ar (3 Marks)
(Ans) Metallic solid - Ag
Covalent solid - Quartz
Molecular solids - I2, Ar, SO2
Ionic solids - MgO
(Q.38) (i) What are voids?
(ii) How a tetrahedral void is different from octahedral void?
(iii) Draw structure of tetrahedral and octahedral void. (3 Marks)
(Ans) (i) Atomsand ions are spherical in shape. A crystal is formed by close packing of atomsor ions.Since,spheres touch each other only at points, some empty space is left between them.This space is called void or hole.
(ii)A tetrahedral void is surrounded by four spheres(atoms), which lie at vertices of regular tetrahedron whereas an octahedral void is surrounded by six spheres(atoms).
(iii)
[pic](Q.) The density of an atom is 7.2g cm–3. It has bcc structure. The edge length is 288 pm. How many atoms of element does 208g of element has?
(3 Marks)
(Ans)
[pic]
(Q.39) Find the type of lattice for cube having edge length of 400 pm, atomic wt. = 60 and density = 6.25 g/cc.
(3 Marks)
(Ans)
Let the no. of atoms in a unit cell = x
[pic]Mass of one unit cell = [pic]
= [pic]
Volume of unit cell = (edge length) 3 = [pic]
= 64 x 10-24 cm3
Density = [pic]
or, Mass = [pic]
[pic]= [pic]
[pic][pic]
= 4
[pic]The unit cell has4 atoms
[pic]It is face centered cubic lattice.
(Q.40) A mineral contains Ca, O and Ti. In its unit cell oxygen atoms are present at face centres, calcium atoms at corners and titanium atoms at centre of cube. Find the oxidation number of titanium in the mineral.(3 Marks)
(Ans) No. of Ca atoms = [pic]
No. of O atoms = [pic]
No. of Ti atoms = [pic]
[pic]Formula of mineral is CaTiO3
Let oxidation number ofTi = x
[pic]In CaTiO3
+2 + x + (-2[pic]3) = 0
[pic]x = +4
[pic]Oxidation state of titanium is + 4 in this mineral.
(Q.41) A metal oxide crystallizes in a hexagonal close packed array of oxide ions with two out of every three octahedral holes occupied by metal. Find formula of metal oxide. (3 Marks)
(Ans)
[pic]
(Q.42) A metal has cubic lattice. Edge length of lattice cell is 2A0. The density of metal is 2.4g cm–3.How many units cell are present in 200g of metal.(3 Marks)
(Ans)
[pic]
(Q.43) The density of NaCl crystal is 2.155g cm–3 and distance between Na+ and Cl– is 280 pm. Find value of Avogadro’s number. (3 Marks)
(Ans) NaCl has fcc structure.
In fcc, a (edge length) = [pic]
= [pic]pm
= 560 pm
[pic]
For fcc , Z = 4, Na = Avogadro number =?
[pic]
(Q.44) In a face centered cubic lattice atoms of A occupy corner of cell and that of B occupy face centers. One of the A atoms is missing from one corner of a unit cell. Find the simplest formula of compound. (3 Marks)
(Ans)
[pic]
**********************************
Unit-2 mm - 5
SOLUTIONS
|Solid Solutions |Gas in solid ( Solution of hydrogen in palladium |
| |Liquid in solid ( Amalgam of mercury with sodium |
|Temp. Vs Conc. |Mass %, ppm, mole fraction and molality are independent of temperature, whereas molarity depends on |
| |temperature. This is because volume depends on temperature. |
|Henry’s law. |At a constant temperature, the solubility of a gas in a liquid is directly proportional to the pressure |
| |of the gas. p = KH . x |
| |KH = Henry’s law constant ( greater the KH value means lower the solubility.) |
|Application of Henry’s law. |1.To increase the solubility of CO2 in soft drinks, the bottle is sealed under high pressure. |
| |2. To avoid bends, the tanks used by scuba divers are filled with air diluted with helium |
|Temp and Solubilty of gas |Solubility of gas increases with decrease of temperature. It is due to this reason that aquatic species |
| |are more comfortable in cold waters rather than in warm waters. |
|Raoult’s law for volatile liquids |The partial vapour pressure of each component in the solution |
| |is directly proportional to its mole fraction p1 α x1 p1 = p10 x1 |
|Ideal Solutions |The solutions which obey Raoult’s law over the entire range of concentration are known as ideal |
| |solutions. ( For ideal solution ΔmixH = 0, ΔmixV = 0) |
| |Example : Solution of n-hexane and n-heptane, |
|Non-ideal Solutions |Positive deviation : A-B interactions are weaker than those between A-A or B-B, |
| |Example - Mixtures of ethanol and acetone |
| |Negative deviations : Forces between A-A and B-B are weaker than those between A-B |
| |Example- mixture of phenol + aniline. a mixture of chloroform +acetone |
|Azeotropes |Mixtures have same composition in liquid and vapour phase and boil at a constant temp. |
| |minimum boiling azeotrope(positive deviation) eg- 95% aq ethanol |
| |maximum boiling azeotrope(negative deviation) eg- 68% aq nitric acid |
|Colligative properties |Depend on the number of solute particles not upon their nature. |
|Osmosis |Solvent flows through the semi permeable membrane from pure solvent to the solution. |
|Osmotic pressure |The extra pressure applied on the solution that just stops the flow of solvent is called osmotic |
| |pressure of the solution |
|Isotonic solutions |Two solutions having same osmotic pressure |
|Hypertonic |Higher osmotic pressure than a particular soln |
|Hypotonic |Lower osmotic pressure than a particular soln |
|Reverse Osmosis |The direction of osmosis can be reversed if a pressure larger than the osmotic pressure is applied to |
| |the solution side. That is, now the pure solvent flows out of the solution |
| |Application : Desalination of sea water |
|van’t Hoff factor ( i ) |ratio of normal molar mass to experimentally determined molar mass or as the ratio of observed |
| |colligative property to the calculated colligative property. |
(Q1) Define binary solution? (1 Mark)
(Ans)Binary solution is a solution containing only one solute dissolved in a solvent.
(Q2) What is molarity? (1 Mark)
(Ans) The number of moles of solute dissolved in one litre or 1dm3 of solution is known as molarity.
(Q3) What do you understand by saying that molality of a solution is 0.2? (1 Mark)
(Ans) This means that 0.2 mol of the solute is dissolved in 1Kg of the solvent.
(Q4) Why is the vapour pressure of a liquid remains constant at constant temperature? (1 Mark)
(Ans) At equilibrium, the rate of evaporation = rate of condensation. Hence the vapour pressure of a liquid is constant at constant temperature.
(Q5) Define Azeotropes? (1 Mark)
(Ans) Constant boiling mixtures are called Azeotropes.
(Q6) Which substance is usually added into water in the car radiator to act as antifreeze? (1 Mark)
(Ans) Ethylene glycol is usually added into water in the car radiator to act as antifreeze.
(Q7) Which liquids form ideal solution? (1 Mark)
(Ans) Liquids having similar structure and polarities.
(Q8) Which property of solution depend only upon the number of moles of solute dissolved and not on the nature of the solute? (1 Mark)
(Ans) Colligative properties.
(Q9) Write one example each of solid in gas and liquid in gas solution? (1 Mark)
(Ans) Solid in gas e.g. Camphor in nitrogen gas.
Liquid in gas – e.g. Chloroform mixed with N2 gas
(Q10) What is molal elevation constant or ebullioscopic constant? (1 Mark)
(Ans) The elevation in boiling point which takes place when molality of the solution is unity, is known as ebullioscopic or molal elevation constant.
(Q) Define van’t Hoff factor. (1 Mark)
(Ans) The ratio of the observed colligative property to the theoretical value is called van’t Hoff factor.
(Q11) Two liquids A and B boil at 1200c and 1600c respectively. Which of them has higher vapour pressure at 700 c? (1 Mark)
(Ans)Lower the boiling point, more volatile it is .So liquid A will have higher vapour pressure at 700c.
(Q12) What happens when blood cells are placed in pure water? (1 Mark)
(Ans) Water molecules move into blood cells through the cell walls. So, blood cells swell and may even burst.
(Q13) What is the effect of temperature on the molality of a solution? (1 Mark)
(Ans) No effect.
(Q14) Write Henry’s law. (1 Mark)
(Ans) The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas at a given temperature.
(Q15) What is the relation between normality and molarity of a given solution. (1 Mark)
(Ans) Normality = 2 x molarity.
(Q16) What is an antifreeze? (1 Mark)
(Ans) An antifreeze is a substance which is added to water to lower its freezing point. e.g. Ethylene glycol
(Q17) Why cutting onions taken from the fridge is more comfortable than cutting onions lying at room temperature? (1 Mark)
(Ans) The vapour pressure is low at lower temperature. So, less vapours of tear – producing chemicals are produced
(Q18) What will be the van’t Hoff factor for O.1 M ideal solution? (1 Mark)
(Ans) Van't Hoff factor = 1, because ideal solution does not undergo dissociation or association.
(Q19) Name the substances which are used by deep sea divers to neutralize
the toxic effects of nitrogen dissolved in the blood. (1 Mark)
(Ans) Theyusemixture of helium andoxygen to neutralize the harmful effects of nitrogen.
(Q20) Why is Anoxia disease very common at higher altitudes? (1 Mark)
(Ans) Anoxia is very common at higher altitudes because of lower partial pressure of oxygen at higher altitudes.
(Q21) What is the optimum concentration of fluoride ions for cleaning of tooth? (1 Mark)
(Ans) The optimum concentration of fluoride ions for the cleaning of tooth is 1.5 ppm.
[If it is more than 1.5 ppm it can be poisonous and if less than 1.5 ppm it isineffective.]
(Q22) What happens to blood cells when they are placed in water containing less than 0.99% (mass/volume) salt? (1 Mark)
(Ans) The blood cells collapse due to loss of water by osmosis when placed in water containing less than 0.9% (mass/volume) salt.
(Q23) Why is molality generally preferred over molarity as unit for expressing concentration of solutions? (1 Mark)
(Ans) Molality is preferred over molarity as unit for expressing concentration of solutions because it involves mass termwhich is not affected by change in temperature while molarity involves volume termwhichchanges with temperature.
(Q24) Calculate the van't Hoff factor of K4[Fe(CN)6]. (1 Mark)
(Ans) K4[Fe(CN)6][pic]4 K + + [Fe(CN)6] 4-
Since one molecule of K4[Fe(CN)6] dissociates to produce 5 ions, the value of van't Hofff factor is 5.
(Q25) Name the law which explains the relationship between solubility of a gas in a liquid and pressure above the liquid surface. Also write the name of the variable which is kept constant for this law. (1 Mark)
(Ans) This is Henry’s law and temperature is kept constant for this law.
[According to Henry's law the partial pressure of gas in vapour phase is proportional to the mole fraction of gas in the solution at constant temperature.]
(Q26) How does Henry constant vary with the solubility of gas in the solution at a given pressure?(1 Mark)
(Ans) Higher the value of “Kh” (Henry constant), lower is the solubility of gas in solution.
(Q27) What care should be taken while preparing intravenous injection? (1 Mark)
(Ans) They should be prepared in aquatic medium and salt concentrations shouldbe same as blood plasma levels.
(Q28) Why osmotic pressure is better technique for determination of molar mass of biomolecules? (1 Mark)
(Ans) Osmotic pressure is better technique for the determination of molar mass of biomolecules because they are generally not stable at higher temperatures and have poor solubility. Therefore, other techniques like elevation in boiling point and depression in freezing point cannot be used to determine molecular masses of biomecules.
(Q29) What will be the molecular mass of acetic acid when it is dissolved in benzene? (1 Mark) (Ans) Normal molecular mass of acetic acid (CH3COOH) is 60. It dimerises when dissolved in benzene.Therefore, molecular mass of acetic acid will be 120 when it is dissolved in benzene.
(Q30) How does increase in temperature affects the solubility in endothermic and exothermic dissolution of substances? (1 Mark)
(Ans) The solubility in endothermic dissolution increases while in exothermic it decreases.
(Q31) What will be the shape of graph which is obtained by ploting partial pressure of a gas against mole fraction of gas in solution? (1 Mark)
(Ans) It is a straight line sincepartial pressure of a gasand mole fraction of gas are directly proportional to each other.
(Q32) Aquatic animals are more comfortable in cold water than in warm water. Explain? (1 Mark)
(Ans) This is because “Kh” (Henry constant) values for both N2 and O2 increase with increase in temperature indicating that the solubility of gases increases with decrease intemperature.
(Q33) Deep sea divers are advised not to come to surface immediately from deep waters. Why? (1 Mark)
(Ans) Deep sea divers are advised not to come to surface immidiately from deep waters because sudden change in outside pressure can be fatal for divers because N2 will bubble out of blood vessels causing severe pain and can be dangerous.
(Q34) What are colligative properties? Name them. (2 Marks)
(Ans) The properties of solute which depend upon the number of particles present in definite amount of solvent but not on the chemical nature of solute are called colligative properties. They are-
(i) Relative lowering of vapour pressure (ii) Elevation in boiling point
(iii) Depression in freezing point (iv) Osmotic pressure
(Q35) Which is better method for expressing concentration of solution – Molarity or Molality? (2 Marks)
(Ans)
[pic]
Volume changes with temperature whereas mass does not change with temperature. So molality, which does not have volume term in it is better method for expressing concentration.
(Q36) Define- (i) Mole fraction (ii) Molality (2 Marks)
(Ans) ( i) The mole fraction of a particular component in a solution is the ratio of the number of moles of that component to the total number of moles of all the components present in the solution.
(ii) Molality of a solution is defined as a number of moles of solute dissolved per 1000g of solvent.
(Q37) The osmotic pressure of human blood is 7.65 atm at 37°C. For injecting glucose solution it is necessary the glucose solution has same osmotic pressure as of human blood. Find the molarity of glucose solution having same osmotic pressure as of human blood. (2 Marks)
(Ans) [pic]= [pic]
Or 7.65 = [pic]
[pic]= [pic]
[pic]= Molarity = 0.30
(Q38) Vapour pressure of two liquid A & B are 120 and 180mm Hg at a given temp. If 2 mole of A and 3 mole of B are mixed to form an ideal soln, calculate the vapour pressure of solution at same temperature. (2 Marks)
(Ans) Total moles = 2 + 3 = 5
P solution = [pic]
= [pic]
= 48 + 108
= 156mm.
(Q39) Density of 1 M soln of glucose 1.18g/cm3. Kf for H2O is 1.86 Km–1. Find freezing point of solution. (2 Marks)
(Ans) Mass of solution =volume x density
=1000 x 1.18
=1180g
Mass of water =1180 - 180
=1000g
[pic][pic]= 1 m
[pic]= [pic]
= [pic]
[pic]= [pic]
= 0 – 1.86 = –1.86°C
(Q40) An aqueous solution freezes at –0.186°C.
Kf = 1.86°, Kb = 0.512. Find elevation in boiling point. (2 Marks)
(Ans) [pic]= 0 – (0.186) = 0.186°C
[pic]= [pic]
Or m = [pic]
[pic]= [pic]
= [pic]
(Q41) Vapour pressure of dilute solution of glucose is 750 mm of Hg at 373K. Calculate the mole fraction of solute. (2 Marks)
(Ans) 373K = 100°C
Vapour pressure of pure water = 760 mm Hg.
P = 750 mm Hg (given)
[pic]
[pic]
Or [pic]
(Q42) Ethylene glycol solution having molality 0.5 is used as coolant in a car. Calculate the freezing point of solution (given Kf=1.86 °C/mole) (2 Marks)
(Ans)
[pic]
(Q46) Calculate the molality of solution prepared by dissolving 18g of glucose 500g of water. (2 Marks)
(Ans) Mol. Wt. of glucose [pic]=(12 x 6) + (1 x 12) + (16 x 6)
= 180
Molality = [pic]= [pic]
(Q47) Find the vant Hoff factor for Al2(SO4)3 (2 Marks)
(Ans)
[pic]
Total ions produced = 2 + 3 = 5
[pic]
(Q48) On a hill station pure water boils at 99.82°C. The Kb of water is 0.513°C Kg mol–1. Calculate the boiling point of 0.69m solution of urea. (2 Marks)
(Ans)
[pic]
Boiling point of solution = Boiling point of water + [pic]
= 99.82 + 0.3539
= 100.17° C
(Q49) A soln of ethanol in water is 1.6 molal. How many gms of ethanol is present in 500g of solution. (2 Marks)
Ans) Mass of ethanol =Molality x Molecular weight
= 1.6 x 46
= 73.6 g
Total of mass of solution = 73.6 + 1000 = 1073.6g
[pic]1073.6g of solution contain 7.6g of ethanol.
[pic]Mass of ethanol in 500g of solution = (73.6 / 1073.6)x 500
[pic]
(Q50) List two conditions that ideal solutions must satisfy. (2 Marks)
(Ans) 1.[pic]Hmixing and[pic]Vmixing of ideal solutions should be zero.
2.They should obey Raoult’s law over the entire range of concentrations.
(Q51) Explain ideal and non-ideal solutions with respect to intermolecular interactions in a binary solution of A and B. (2 Marks)
(Ans) For the given binary solution of A and B, it would be ideal if A-B interactions are equal to A-A and B-B interactions and it would be non-ideal if they are different to each other.
The deviation from ideal behaviour will be positive if A-B interactions are weaker as compared to A-A and B-B. The deviation will be negative if A-B interactions are stronger as compared to A-A and B-B.
(Q52) (i) What are minimum boiling and maximum boiling azeotropes?
(ii) Can azeotropes be separated by fractional distillation? (2 Marks)
(Ans) (i) Minimum boiling azeotropes are the non-ideal solutions showing positive deviation while maximum boiling azeotropes are those which show negative deviation. Because of positive deviation their vapour pressures are comparatively higher and so they boil at lower temperatures while in case of negative deviation, thevapour pressures are lesser and sohighertemperature arerequired for boiling them.
(ii) No, azeotropes can’t be separated by fractional distillation.
(Q53) (i) When a non-volatile solute is added to solvent,there is increase in boiling point of solution.Explain.
(ii) Define ebullioscopic constant and give its units. (2 Marks)
(Ans) (i) When a non-volatile solute is added to a volatile solvent the vapour pressure of pure solvent decreases because a part of the surfaceis occupied by non-volatile solute which can’t volatilise. As a result, thevapour pressure of solution decreases andhence, the solution requires acomparatively higher temperature to boilcausing an elevation of boiling point.
(ii) Ebullioscopic constant isdefined as the elevation in boiling point of a solution of a non-volatile solute when its molality is unity. Its units are K Kg mol-1
(Q54) One molal solution of a given solvent is always less concentrated than one molar solution. Explain. (2 Marks)
(Ans) In one molar solution one gram mole of solute is dissolved in one litre of solution while in case of one molal solution same one gram mole of solute is dissolved in 1000 gm of solvent only, which on considering normal density parameters of water, can’t be lesser in amount than solvent part present in one litre solution.Therefore,more amount of solvent is present in one molal solution than in one molar solution.
(Q55) State Raoult’s law. Prove that it is a special case of Henry’ law? (2 Marks)
(Ans) Raoult’s law states that partial pressure of a volatile component of a solution is directly proportional to its mole fraction. It is a special case of Henry’ law because it becomes the same when “Kh” (Henry constant) is equal to pressure of pure solvent.
(Q56) How did Van’t Hoff explain the abnormal molecular masses of electrolytes like KCl in water and non-electrolytes like benzoic acid in benzene. (2 Marks)
(Ans) The molecular mass of KCl in aqueous medium has been observed to be almost half than expected and it has been explained as dissociation of KCl into K+ ions and Cl- ions when actual no. of particles become double and so become the colligative properties but since molecular mass is always inversely proportional to colligative property it becomes almost half.
In case of benzoic acid in benzene, association of molecules take place when they dimerise and their no. becomes almost half and so molecular mass doubles as a result.
(Q57) Calculate molality of an aerated drink having 2.5 gm of carbonic acid dissolved in 150 gm of water. (2 Marks)
(Ans) Molality= moles of solute / Mass of solvent in Kg
= [(2.5 / 62.)/ (150 / 1000)]
= 0.268.
(Q58) When 3.49 gm of a non-volatile solute was dissolved in 125 gm of benzene, its boiling raised by 1.23K. Calculate the molecular mass of non-volatile solute. (Kb for benzene is 2.53 K kg Mol-1) (2 Marks)
(Ans)
[pic]
(Q59) When 5.29 g of a non-volatile solute was dissolved in 400 g of water, its freezing point decreased by 1.79 K. Calculate the molecular wt of solute if Kf for water is 1.86 KkgMol-1 (2 Marks)
(Ans)
[pic]
(Q60) Calculate the mass of ethanol which is present in 500g of 1.6m solution of ethanol in water.(2 Marks)
(Ans)
[pic]
(Q61) One litre seawater is found to contain 5.8 [pic] 10-3g of dissolved oxygen. Calculated the ppm of dissolved oxygen in seawater. (Density of seawater = 1.03 g/cc). (2 Marks)
(Ans)
[pic]
(Q62) When a non-volatile solute is added to pure water its vapour pressure decreases by 4 mm Hg. Calculate molality of solution. (Vapour pressure of pure water is 40mm Hg) (2 Marks)
(Ans)
[pic]
(Q63) What are azeotropes? Give an example of maximum boiling azeotrope. (2 Marks)
(Ans) Azeotropes are binary mixtures having the same composition in liquid and vapour phase and boil at a constant temperature. Mixture of nitric acid and water is an example of maximum boiling azeotrope.
(Q64) A decimolar solution of NaCl exerts OP(∏) of 4.6 atm at 300K. Find the degree of dissolution. (3 Marks)
(Ans) NaCl → Na+ + Cl -
Initial moles 1 0 0
Moles at [pic][pic][pic]
Equilibrium
Total moles at equilibrium = [pic]
[pic]
[pic]
[pic]
[pic]
[pic][pic]
= 0.868 = 86.8%
(Q65) An aqueous solution of a non-volatile and non-electrolyte substance boils at 100.5°C. Calculate osmotic pressure of this solution at 27°C. Kb (for water) per 1000g = 0.50. (3 Marks)
(Ans) [pic]= [pic]
= 100.5 –100 = 0.5°C
[pic]= [pic]
[pic]Molality of solution = 1
[pic]Solvent is water.
[pic]density of solution = 1
Volume of solution = volume of solvent = 1000/1 = 1000ml = 1 L
[pic]
[pic]= nRT
[pic]= [pic]
(Q66) The vapour pressure of benzene at certain temperature is 640mm Hg. To 39.08 of benzene, non-volatile and non-electrolyte solid-weighing 2.175g was added. The vapour pressure of solution was 600mm of Hg. Find the mass of the solute? (3 Marks)
(Ans)
[pic]
or [pic]= [pic]
[pic]= [pic]
[pic]= [pic]
or m = [pic]
(Q67) The vapour pressure of water at 296K is 19.8 mm of Hg, 0.1 mol of glucose dissolved in 178.2g of water. Calculate the vapour pressure of resultant solution. (3 Marks)
(Ans) n glucose = 0.1 (given)
n H2O = [pic]
x (water) = [pic]
(Q68) A solution is prepared by dissolving 30g of non-volatile non-electrolyte solute in 90g water. The vapour pressure of solution was 2.8 K Pa at 298K. When 18g of water was further added to it, the vapour pressure became 2.9 k Pa at 298K. Calculate molar mass of solute. (3 Marks)
(Ans) [pic]
(When A is for H2O) n = moles of solute
2.8 = [pic]________ (1)
2.9 = [pic]_______ (2)
Dividing eq. (1) and (2), we get
[pic]= [pic]
[pic]n = [pic]
[pic]Mass of solute = 30 and molecular mass = 23
(Q69) Vapour pressure of pure water is 40mm. If a non-volatile solute is added to it, vapour pressure falls by 4 mm. Calculate molality of solution. (3 Marks)
(Ans)
[pic]
[pic]The solution has 0.1 moles of solute in 0.9 moles of water.
Mass of water = [pic]
Molality of solution = [pic]
= 6.17m
(Q70) Conc. H2SO4 has a density 1.9g/ml and is .99% H2SO4 by weight. Find molarity of solution. (3 Marks)
(Ans) Mass of 1000 ml of H2SO4 = density [pic]volume
=[pic]
= 1900 g
Mass of H2SO4 present in 1900 g (1L) of H2SO4
= [pic]
= 1881 g
Mole of H2SO4 present in 1L = Molarity = [pic]
= [pic]
= 19.197 M
(Q710) A solution contains 25% water, 25% ethanol and 50% acetic acid by mass. Find mole fraction of each of the component. (3 Marks)
(Ans)
Moles of water = n1 = [pic]
Moles of [pic]= n2 = [pic]
Moles of [pic]= n3 = [pic]
Total moles in solution = [pic]
Mole fraction of water = [pic]
Mole fraction of [pic]= [pic]
Mole fraction of [pic]= [pic]
(Q72) Which will have more osmotic pressure and why? Solution prepared by dissolving 6g/L of CH3COOH or Solution prepared by dissolving 7.45g/L of KCl (3 Marks)
(Ans)
Moles of CH3COOH = [pic]
Moles of KCl = [pic]
[pic]Molar concentration of both the solutions is same.
KCl ionizes into K+ and Cl– where as CH3COOH does not ionize:
[pic]Osmotic pressure is colligative property.
[pic]Its value depend on number of particles.
Since, KCl produces more ions so, osmotic pressure of KCl will be more than that of CH3COOH .
(Q73) A solution is prepared by mixing 50ml of chloroform and 50ml of acetone. What will be the resulting volume of solution? 100 ml or >100 ml or mol L-1s–1 |
|For R(P | |
|Rate law / Rate equation / |Rate law is the expression in which reaction rate is given in terms of molar concentration of |
|Rate expression |reactants with each term raised to some power, which may |
| |or may not be same as the stoichiometric coefficient of the reacting species in a balanced chemical|
| |equation. |
|For aA + bB → cC + dD |The rate expression for this reaction is : |
| |Rate α [A]x [B]y => Rate = k [A]x [B]y k is the Rate const. (x , y from expts) |
|Order of a Reaction |The sum of powers of the concentration of the reactants in the rate law expression is called the |
| |order of that chemical reaction. |
| |If Rate = k [A]x [B]y Order = x + y |
|Elementary reactions |The reactions taking place in one step are called Elementary Reactions |
|Unit of rate constant |For n th order reaction : mol1-n Ln-1 s-1 |
|Molecularity of a Reaction |The number of reacting species taking part in an elementary reaction, which must collide |
| |simultaneously in order to bring about a chemical reaction is called molecularity of a reaction |
| |(values are limited from 1 to 3) |
|Rate Determining Step |The overall rate of the reaction is controlled by the slowest step in a reaction called the rate |
| |determining step |
|Half-life (t1/2) |The half-life of a reaction is the time in which the concentration of a reactant is reduced to one |
| |half of its initial concentration. It is represented as t1/2. |
|Zero Order Reactions |K =[R0] – [R] |
|(Integrated Rate Equation) |t Mol L-1 Sec-1 |
| | |
|First Order Reactions | |
|(Integrated Rate Equation) |K = 2.303log [A0] |
| |t [A] |
|Dependence of t1/2 on [R]0 |For zero order : t1/2 α [R]0. For first order reaction t1/2 is independent of [R]0 |
|Example of Zero Order |The decomposition of gaseous ammonia on a hot platinum surface is a zero order reaction at high |
|Reactions |pressure. Rate = k [NH3]0 = k |
|Radioactive decay |All natural and artificial radioactive decay of unstable nuclei take place by first order kinetics |
|Pseudo First Order |When one of two reactants is present in large excess. During the hydrolysis of 0.01 mol of ethyl |
|Reaction |acetate with 10 mol of water The concentration of water does not get altered much during the course|
| |of the reaction and the reaction behaves as first order reaction. Such reactions are called pseudo |
| |first order reactions. |
|Activation Energy |Activation energy is given by the energy difference between activated complex and the reactant |
| |molecules |
|Arrhenius equation |k = A e -Ea /RT (exponential form) |
| |ln k = – Ea/RT + ln A (logarithmic form) |
| |A is the Arrhenius factor or the frequency factor or pre-exponential factor |
|e -Ea /RT |The factor e -Ea /RT corresponds to the fraction of molecules that have kinetic energy greater than|
| |Ea |
|Action of catalyst |Catalyst provides an alternate pathway or reaction mechanism |
| |by reducing the activation energy between reactants and products and hence lowering the potential |
| |energy barrier |
|Collision frequency (Z) |The number of collisions per second per unit volume of the reaction mixture. |
| |For A + B → Products Rate = P.ZAB e−Ea/ RT P is probability or steric factor ZAB is |
| |collision frequency of reactants, A and B |
Important questions
Q1. Define Pseudo order reaction?
Ans:- Reaction showing higher order but actually follow lower order is known as Pseudo order
Q2. The decomposition reaction of ammonia gas on platinum surface has a rate
constant = 2.3 x 10-5 L mol-1s-1. What is the order of the reaction?
Q3 Mention the factors that affect the rate of a chemical reaction.
Q4 From the rate expression for the following reactions determine their order
of reaction and dimensions of the rate constants.
a) H2O2 (aq) + 3 I - (aq) + 2H+ ( 2H2O (l) + 3I-1 Rate = k [H2O] [I-]
b) CH3 CHO (g) ( CH4(g) + CO(g) Rate = k [CH3 CHO]3/2
Q5.. A reaction is first order in A and second order in B.
i) Write differential rate equation.
ii) How is the rate affected when concentration of B is tripled?
iii) How is the rate affected when the concentration of both A and B is
doubled?
Q6. The decomposition of NH3 on platinum surface is zero order reaction.
What are the rates of production of N2 and H2 if k = 2.5 x 10-4 mol L-1 S-1?
Q7 . Derive the Integrated rate equation for first order reaction. Also find half
life period and plot the graph associated to it.
Q8. For a first order reaction, show that time required for 99% completion is
twice the time required for the completion of 90% of reaction.
Q9. A first order reaction has a rate constant 0.0051min-1 .If we begin with 0.10
M concentration of the reactant, what concentration of the reactant will be
left after 3 hours.
Q10. The half-life for radioactive decay of 14C is 5730 years. An archaeological
Artifact containing wood had only 80% of the 14C found in a living tree.
Estimate the age of the sample
Q11. What is the effect of temperature on the rate constant of a reaction? How
Can this temperature effect on rate constant be represented quantitatively ?
Q12. The rate of a reaction quadruples when the temperature changes from 293K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature.
Q13. A first order reaction takes 40 min for 30% decomposition. Calculate t1/2..
Q14 (a) Distinguish between order of reaction & Molecularity.
(b) For a decomposition reaction the values of rate constant k at two different temperatures are given below:k1 =2.15 x 10-8 L mol-1s-1 at 650K, k2 =2.39 x 10-7 L mol-1s-1 at 700K Calculate the value of Activation Energy for this reaction.
Q15. (i) Write short notes on the following:
(a) Activation energy of a reaction (b) Elementary step in a reaction (c)Rate of a reaction
(ii) The following result has been obtained during the kinetic studies of the
reaction2A + B ( C+D
|Experiment |[A] mol L-1 |[B] mol L-1 |Intial rate |
| | | |mol L-1min-1 |
|I |0.1 |0.1 |6.0x10-3 |
|II |0.3 |0.2 |7.2X10-2 |
|III |0.3 |0.4 |2.88X10-1 |
|IV |0.4 |0.1 |2.40X10-2 |
Determine the rate law and rate constant for the reaction.
Q16 From the concentrations of C4H9Cl (butyl chloride) at different times given
below, calculate the average rate of the reaction:C4H9Cl + H2O ( C4H9OH + HCl
during different intervals of time.t/s 0 50 100 150 200 300 400 700 800
[C4H9Cl]/mol L–1 0.100 0.0905 0.0820 0.0741 0.0671 0.0549 0.0439 0.0210 0.017
Ans We can determine the difference in concentration over different intervals
of time and thus determine the average rate by dividing Δ [R] by Δt
Unit - 5
SURFACE CHEMISTRY MARKS-4
(Q.) What is meant by critical temperature of gas? (1 Mark)
(Ans) Critical temperature is the minimum temperature above which a gas cannot be liquefied howsoever high the pressure may be applied.
(Q.) Give the expression for Fruendlich adsorption isother (1 Mark)
(Ans) x/m= kp1/n
(Q.) What do x and m represent in the expression x/m=kp1/n (1 Mark)
(Ans) ‘m’ is the mass of the adsorbent and ‘x’ is the number of moles of the adsorbate when the dynamic equilibrium has been achieved between the free gas and the adsorbed gas.
(Q.) Why is heterogeneous catalysis also known as surface catalysis (1 Mark)
(Ans) In heterogeneous catalysis the reaction always starts at the surface of the catalyst. So, it is also known as surface catalysis.
(Q.) What is a hydrosol? (1 Mark)
(Ans) A colloid in which the dispersion medium is water is known as hydrosol.
(Q.) Define peptization? (1 Mark)
(Ans) Peptization is a process of converting a precipitate into colloidal particlesby adding suitable electrolyte.
(Q.) Define Brownian movement? (1 Mark)
(Ans) Brownian movement can be defined as continuous zig- zag movement of the colloidal particles in a colloidal sol.
(Q.) Why is Brownian movement important? (1 Mark)
(Ans) Brownian movement opposes the force of gravity and does not allow the colloidal particles to settle down, thus making the colloidal solution stable.
(Q.) Differentiate between adsorption and absorption. (1 Mark)
(Ans) Adsorption Absorption
a)it occurs only at surface a) it is a bulk phenomena
b)concentration on the surface b) concentration is same
is more than in the bulk through out the material
(Q.) What is the effect of temperature on adsorption? (1 Mark)
(Ans) Adsorption processes, being exothermic, decreases with increase in temperature.
(Q.) When a finely powdered active carbon is stirred into a solution of a dye, the intensity of color in solution decreases. Why? (1 Mark)
(Ans) The intensity of color in the solution decreases because of gas adsorbedon the surface of carbon.
(Q.) Why do finely divided substances have larger adsorption power? (1 Mark)
(Ans) Finely divided substances have large surface area for adsorption and hence have larger adsorption power.
(Q.) What are zeolites? (1 Mark)
(Ans) Zeolites are aluminosilicates i.e. three dimensional network silicates in which some silicon atoms are replaced by aluminium atoms.
(Q.) Why are zeolites called shape selective catalysts? (1 Mark)
(Ans) Zeolites are called shape selective catalysts because their catalytic action depends upon the size and shape of the reactant and the product molecules as well as on their own pores and cavities.
(Q.) A small amount of silica gel and that of anhydrous CaCl2 are placed separately in two corners of a vessel containing water vapours. What phenomena will occur in the two corners? (1 Mark)
(Ans) Adsorption would occur where silica gel is kept in the vessel where as absorption will occur in the corner where CaCl2 is placed.
(Q.) Name the substance catalysed by Zymase. (1 Mark)
(Ans) Glucose--Zymase->ethyl alcohol.
(Q.) How can colloidal solution of ferric hydroxide be prepared by peptization? (1 Mark)
(Ans) A colloidal sol. of ferric hydroxide can be prepared by adding small quantity of ferric chloride solution to freshly prepared precipitate of ferric hydroxide.
(Q.) What is the cause of Brownian movement? (1 Mark)
(Ans) Brownian movement is caused by the striking of the colloidal particles with the molecules of dispersion medium due to their kinetic energy.
(Q.) Define Tyndall effect? (1 Mark)
(Ans) It is defined as the scattering of light by the colloidal particles present in a colloidal solution.
(Q.) What happens to a gold sol. when gelatin is added to it? (1 Mark)
(Ans) Gold sol. which is lyophobic starts behaving like lyophilic sol.
(Q.) Write down the relation between pressure of the gas and the amount of it adsorbed? (1 Mark)
(Ans) x/m = K P1/n
(Q.) Which adsorption may be a multilayered formation phenomenon? (1 Mark)
(Ans) Physisorption
(Q.) Which is irreversible and why? Physisorption or chemisorption. (1 Mark)
(Ans) chemisorption. Because of the formation of chemical bond.
(Q.) Name the promoter used in Haber’s process? (1 Mark)
(Ans) Molybdenum.
(Q.) What is emulsion? What are their different types? (2 Marks)
(Ans) An emulsion is the colloidal dispersion in which both the dispersed phase and the dispersion mediums are liquids. They can be of two types:-
i) Emulsion of oil in water.
ii) Emulsion of water in oil.
(Q.) How are micelles formed in soap solution? (2 Marks)
(Ans) Soap is sodium salt of fatty acids (RCOONa) which when dissolved in water dissociates to give RCOO- and Na+. The RCOO- consists of polar group COO- which is hydrophilic and stays at the surface and the non polar group R which being hydrophobic stays away from the surface. At high concentrations RCOO- ions are pulled into the solution to form spherical aggregates with R pointing to the centre COO- part remaining outward. This aggregate is known as ionic micelle.
(Q.)How can lyophobic sols be prepared by mechanical disintegration?(2 Marks)
(Ans) The coarse suspension of the substance is introduced in the colloid mill that consists of two metal discs close together rotating at a high speed in the opposite directions. Here the suspension particles are broken to the colloidal size.
(Q.) Differentiate between chemisorption and physisorption? (2 Marks)
(Ans) Physisorption:
a)The forces operating are weak vander Waal’s forces
b)The heat of adsorption is low 20-40 KJ Mol-1
c)Does not require any activation energy
d)Forms multimoleculer layer
Chemisorption:
a)Forces acting are similar to those of chemical bonds
b) The heat of adsorption is high 80-240 KJ Mol-1
c) Requires activation energy
d) Forms unimolecular layer
(Q.) Describe the mechanism of peptization? (2 Marks)
(Ans) When electrolyte is added to the freshly precipitated substance, the particles of the precipitate preferentially absorb one particular type of ions of the electrolyte and get dispersed due to electrostatic repulsions giving particles of colloidal size and hence cause peptization.
(Q.) Give any two reasons for the origin of electrical charge on the colloidal particles. (2 Marks)
(Ans) The two reasons are:
i) Due to electron capture by sol particles during electro dispersion of metals, due to preferential adsorption of ions from solution
ii) Dissociation of colloidal sols.
(Q.) How is the electrical charge of the colloidal particles responsible for the stability of colloidal sols? (2 Marks)
(Ans) The electrical charges of the particles prevent them from coming together due to electrostatic repulsion. All the dispersed particles in a colloidal solution carry the same charge while the dispersion medium has equal and opposite charge.
(Q.) What is demulsification? Name two demulsifiers. (2 Marks)
(Ans) The process of separation of the constituent liquids of an emulsion is called demulsification. Demulsification can be done by centrifugation or boiling.
(Q.) Why lyophilic colloids are called reversible sols while lyophobic sols are called irreversible sols? (3 Marks)
(Ans) In the lyophilic colloids if the dispersed medium is separated from the dispersion medium the sol can be made again by simply remixing with the dispersion medium. So they are called reversible sols.
In lyophobic sols if small amount of electrolyte is added, the sols are readily precipitated and do not give back the colloid by simple addition of the dispersion medium. So they are called irreversible sols.
(Q.) Describe the preparation of the following colloidal solution.
(a) Gold sol (b) Sulphur sol (3 Marks)
(Ans) (a) Preparation of Gold sol :- By the reduction of very dilute solution of silver salts with a suitable reducing agent
2AuCl3 + 3SnCl2 -------------> 2Au + 3SnCl4
Gold sol
(b) Preparation of Sulphur sol :- By the oxidation of H2S in the presence of suitable oxidizing agent like nitric acid, bromine water, etc.
H2S + Br2 --------------> S + 2HBr
H2S + 2HNO3 ------------> 2H2O + 2NO2 + S
(Q.) What are macromolecular and multimolecular colloids? How are they different from associated colloids? (3 Marks)
(Ans) Macromolecular colloids:-
i)They are molecules of large size.
ii)They have lyophobic property.
Multimolecular colloids:-
i) They are formed by the aggregation of large number of atomsor molecules which have diameter less than 1nm.
ii) They have lyophilic property.
Associated colloids:-
i) They are formed by the aggregation of large number of ions in concentrated solution
ii) They contain both lyophilic and lyophobic groups
(Q.) What are lyophilic and lyophobic solutions? Give examples for each.
(3 Marks)
(Ans) Lyophilic solutions are those that can be prepared by directly mixing the dispersed phase with dispersion medium. For example starch dissolved in water.
Lyophobic solutions are those that can not be prepared directly but some special methods are used to prepare them. For example metal sulphides when mixed with a dispersion medium directly do not result in any colloid.
(Q.) "Action of soap is due to emulsification and micelle formation".Comment. (3 Marks)
(Ans) Yes, action of soap is due to emulsification and micelle formation. Soaps are sodium salt of higher fatty acids like sodium stearate, C17H35COO-Na+
[pic]
[pic]
The anionic head of stearate ion (-COO-) is hydrophobic in nature and has great affinity for water, while the hydrocarbon part (C17H35-) is hydrophilic in nature and great affinity for oil,grease etc.When soap is used in water, the anions (C17H35COO-) form micelle and due emulsification encapsulate oil or grease inside. These micelle are removed by rinsing with water; while free dirt (from oil or grease) either settle down or are washed away by water. Thus the main function of a soap is to entrap oil or grease with the micelles through emulsification, thereby freeing dirt from grease and oil.
(Q.) Why the sun looks red at the time of setting? Explain on the basis of colloidal properties. (3 Marks)
(Ans) At the time of setting, the sun is at the horizon. The light emitted by the sun has to travel a longer distance through the atmosphere. As a result, blue part of the light is scattered away by the dust particles in the atmosphere. Hence, the red part is visible.
(Q.) Explain the reason for these: (3 Marks)
(a) Sky looks blue in colour.
(b) Delta is formed at the meeting place of river and sea water.
(c) Blood coagulate on treatment of alum.
(Ans) (a) Sky looks blue in colour because colloidal particles suspended in environment scatter the light and blue light is scattered maximum.
(b) The charged colloidal particles of river water neutralized by ions present in sea water so coagulation take place.
(c) The charged colloidal particles present in blood are neutralized by ions of alum.
UNIT – 6 Marks-3
General Principles and Processes of Isolation of elements
1. Give the name and composition of ore chosen for extraction of aluminium. (1 Mark)
Ans: The ore chosen for the extraction of aluminium is bauxite and its composition is Al2O3.xH2O.
2. What is leaching? (1 Mark)
Ans: Leaching is the process of extracting a substance from a solid by dissolving it in a liquid. In metallurgy leaching is used for the ores that are soluble in a suitable solvent.
3. Why cryolite & fluorospar added to alumina during electrolytic reduction? (1 Mark)
Ans: Cryolite and fluorospar are added to alumina during electrolytic reduction to reduce the melting point of alumina and to increase its conductivity
4. Reduction with C for Cu2O can be done at lower temp. than ZnO. Why? (1 Mark)
Ans: In the Ellingham diagram the curve for Cu2O lies higher than ZnO i.e. for the reduction of Cu2O with C the negative value of Gibbs energy can be reached at a lower temperature than ZnO.
5. Although thermodynamically feasible in practice magnesium metal is not used for the reduction of alumina. Why? (1 Mark)
Ans: Magnesium can reduce alumina at the temperature above the intersection point of the curves for Al2O3 and MgO in the Gibbs Energy vs T plot (Ellingham diagram). But the temperature at which this is feasible is too high to be achieved economically and is also technologically difficult. So this reduction is not done.
6. What is the significance of leaching in extraction of aluminium? (1 Mark)
Ans: In the extraction of aluminium leaching is used for the concentration of ore by removing the impurities i.e. silica, iron oxides and titatinium oxides.
7. Define Metallurgy. (1 Mark)
Ans: Metallurgy is the process of extraction of metals from their ores that includes various steps.
8. Why is hydraulic washing a type of gravity separation? (1 Mark)
Ans: The process of hydraulic washing is based on the differences in gravity of the ore and the gangue particles and so is known as gravity separation.
9. What is the use of van Arkel method? (1 Mark)
Ans: Van Arkel method is used for removal of impurities like oxygen and nitrogen from the metals like zirconium and titanium.
10. How is distillation used for metal refining? (1 Mark)
Ans: Distillation is used for the metals with boiling point lower then the impurities. So the metals can be evaporated and separately obtained as distillate.
11. Why do the anodes used in the electrolytic cell for the reduction of alumina need to be replaced regularly? (1 Mark)
Ans: The oxygen liberated at the anode during the reduction of alumina, reacts with the carbon of the anode to form CO and CO burns away the anode and hence the anodes need to be replaced.
12. What is the role of depressant in froth floatation process? (1 Mark)
Ans: In froth floatation process the depressant selectively prevents one of the ores from coming to the froth in a mixture of two ores hence enabling the separation of the other one with the froth.
13. State the role of silica in the metallurgy of copper. (1 Mark)
Ans: Silica in the metallurgy of copper helps in removal of iron oxide as iron silicate (slag).
14. What is the role of graphite rods in the electrometallurgy of aluminium?(1 Mark)
Ans: In the electrometallurgy of aluminium graphite rods act as anodes in the electrolytic cell of reduction and are the site for release of oxygen
15. Give an example when an element is extracted by oxidation. (1 Mark)
Ans: Extraction of chlorine from brine is based on oxidation.
16. What will happen if aqueous solution of NaCl is subjected to electrolysis?(1 Mark)
Ans: If aqueous Solution of NaCl is subjected to electrolysis, Cl2 will be obtained with NaOH and H2 gas as the side products.
17. What is refining of metals? (1 Mark)
Ans: Refining of metal is the process of purification of a metal extracted from its ore.
18. What is vapour phase refining? (1 Mark)
Ans: Vapour phase refining is the method of metal refining by changing the metal into volatile compound that can be collected separately leaving behind the impurities and can be decomposed to give the pure metal.
19. Give the principle underlying the process used for refining of gallium. (1 Mark)
Ans: The process used for the refining of gallium is zone refining and the principle underlying it is that the impurities are more soluble in the melt than in solid state of the metal.
20. State the principle on which the chromatographic methods of metal refining are based? (1 Mark)
Ans: Chromatographic methods of metal refining are based on the principle that different components of a mixture are differently adsorbed on an adsorbent
21. Which is the purest form of iron and what are its uses? (1 Mark)
Ans: The purest form of iron is wrought iron & is used in making anchors, wires, bolts etc.
22. What are minerals and how are they different from ores? (2 Marks)
Ans: Minerals are the naturally occurring chemical substances in the earth’s crust obtained by mining. Its different from ores, as ores are the minerals that are used for the extraction of metals profitably.
23. Name one ore each for iron & copper & give their chemical compositions. (2 Marks)
Ans: The ore of iron is hematite- Fe2O3 and the ore for copper is copper pyrites- CuFeS2.
24. What is the purpose of adding collectors and froth stabilisers during froth floatation? Give an example for each. (2 Marks)
Ans: During froth floatation process collectors like pine oil and fatty acids are added to enhance non wettability of the mineral particles and the froth stabilisers like cresol and aniline stabilise the froth.
25. How can the ores ZnS and PbS be separated from a mixture using froth floatation process? (2 Marks)
Ans: During the froth floatation process a depressant like NaCN is added to the tank. The depressant selectively prevents ZnS from coming to the froth but allows PbS to come to the froth and hence helps the separation of PbS with the froth.
26. Give the equations involved in the concentration of bauxite ore. (2 Marks)
Ans: i) Al2O3(s) + 2NaOH + 3H2O[pic] 2Na[Al(OH)4](aq)
ii) 2Na[Al(OH)4](aq) + CO2(g)[pic] Al2O3.xH2O(s) + 2NaHCO3
iii) Al2O3.xH2O(s)[pic] Al2O3(s) + xH2O
27. Give one reaction each for roasting and Calcination. (2 Marks)
Ans: Calcination: ZnCO3[pic] ZnO(s) + CO2
Roasting: 2ZnS + 3O2[pic] 2ZnO + 2SO2
28. Why is coke preferred over CO for reducing FeO? (2 Marks)
Ans: According to Ellingham diagram the point of intersection of the curves of C, CO and Fe, FeO lies at temperature lower than that of the point of intersection of CO,CO2 and Fe, FeO curves. This means the reduction of FeO will occur at much lower temperature with C than with CO. So C is preferred to CO for reduction.
29. How is cast iron different from pig iron? (2 Marks)
Ans: Pig iron has 4% carbon and can be easily cast into verity of shapes. Whereas cast iron has lower carbon content and is extremely hard and brittle.
30. Give the reactions that occur after the copper matte have been fed into silica lined converter. (2 Marks)
Ans: 2FeS+3O2 [pic]2FeO + 3O2
FeO + SiO2 [pic]FeSiO3
2Cu2S + 3O2 [pic]2Cu2O + 2SO2
2Cu2O + Cu2S [pic]6Cu + SO2
31. Give the reactions taking place at the anode and the cathode during the electrolytic reduction of alumina. (2 Marks)
Ans: Anode: C(s) + O2-(melt) [pic]CO(g) + 2e-
C(s) + 2O2-(melt) [pic]CO2(g) + 4e-
Cathode: Al3+(melt) + 3e- [pic]Al(l)
32. Explain the process of magnetic separation for concentration of ores. (3 Marks)
Ans: In magnetic separation ore is carried over a conveyer belt which passes over a magnetic roller. If either the ore or the gangue is capable of being attracted by the magnetic field then it will collect near the roller and the particles showing non magnetic behaviour will be collected away from the roller.
33. Differentiate between roasting and Calcination. (3 Marks)
Ans: Calcination:
i) it involves heating of the ore in the absence of air
ii) it is generally used for carbonate ores
Calcination: ZnCO3[pic] ZnO(s) + CO2
Roasting:
i) it involves the heating of the ore in the presence of air
ii) it is generally used for sulphide ores
Roasting: 2ZnS + 3O2[pic] 2ZnO + 2SO2
34. Give the reactions involved in the reduction of iron oxide to give iron in a blast furnace. (3 Marks)
Ans: The reactions are as follows:
C + O2[pic] CO2
CaCO3 [pic]CaO + CO2
CO2+ C[pic] CO
3Fe2O3 + CO [pic]Fe3O4 +CO2
Fe3O4 + CO [pic]3FeO + CO2
FeO +CO [pic]Fe + CO2
FeO + C [pic]Fe + CO
CaO + SiO2 [pic]CaSiO3
35. How is copper extracted from low grade ores and scraps? (3 Marks)
Ans: For extraction of copper from low grade ores and scraps the ore is first leached out using acid or bacteria. The solution containing Cu2+ is treated with scarp iron or H2 and Cu is obtained.
Cu2+(aq) + H2(g) [pic]Cu(s) + 2H+(aq)
Cu2+ + Fe [pic]Cu(s) + Fe2+
36. How is gold extracted from its ore? (3 Marks)
Ans: Extraction of gold involves leaching the metal with CN- giving metal complex.
4Au + 8CN-(aq) + 2H2O + O2(g) [pic]4[Au(CN)2]-(aq) + 4OH-(aq)
the metal is later recovered by displacement method with zinc acting as reducing agent.
2[ Au(CN)2]-(aq) + Zn(s) [pic]2Au(s) + [Zn(CN)4]- (aq)
37. Describe the method used for refining copper metal. (3 Marks)
Ans: Copper metal is refined by using electrolytic method with impure copper metal as anode and the pure copper metal strip as cathode. The electrolyte is acidified copper sulphate solution. Copper dissolves from the anode into the electrolyte and get reduced and deposited on the cathode as pure metal.
Anode: Cu [pic]Cu2+ + 2e-
Cathode: Cu2+ + 2e- [pic]Cu
Impurities deposit as anode mud.
38. How is nickel refined? (3 Marks)
Ans: Nickel is refined by Mond’s process which is based upon vapour phase refining.
In this process nickel is heated in stream of carbon monoxide giving a volatile complex, leaving the impurities behind. The complex is further subjected to higher temperature so that it gets decomposed to giving pure metal. 330-350K
Ni + 4CO --------------> Ni(CO)4
450-470K
Ni(CO)4 ------------------> Ni + 4CO
39. Describe briefly column chromatography. (3 Marks)
Ans: Column chromatography is the method of chromatographic refining of metals available in minute quantities and the impurities are not chemically very much different from the element. In this process the column of Al2O3 is prepared in glass tube that forms the stationary phase and the solution of the components to be separated are taken as solution that forms the mobile phase. The components would separate out based on their different solubilities in the mobile phase and the stationary phase.
40. What criterion is followed for the selection of the stationary phase in chromatography? (3 Marks)
Ans: Stationary phase is the immobile and immiscible phase in chromatographic method. Stationary phase is such chosen that the components to be separated present in the mobile phase have different solubilities in the mobile phase and the stationary phase.
41. How is zinc extracted from zinc blende? (3 Marks)
Ans: Zinc blende is ZnS. For the extraction of zinc from zinc blende, the ore is first concentrated by the method of froth floatation. The concentrated ore is then roasted by heating the ore in the presence of oxygen to give ZnO releasing SO2. The ZnS is further reduced using coke at temperature of 673k giving zinc metal.
2ZnS + 3O2 [pic]2ZnO + 2SO2
ZnO + C [pic]Zn + CO
UNIT-7 MARKS-8
p-Block Elements
Ques: Why is N2 inert at room temperature? (1 Mark)
Ans: N2 is inert at room temperature because of high bond enthalpy due tothe presence of triple bond in N2.
Ques: Why are the axial bonds in PCl5 longer than equatorial bonds? (1 Mark)
Ans: Axial bonds are longer than equatorial bonds in PCl5 because of the higher repulsion experienced by the axial bond pairs as three pair of electrons repel them whereas only two pair of electrons repel the equatorial bonds
Ques: What happens when SO2 passed through an aqueous solution of Fe3+ salt? (1 Mark)
Ans: 2Fe3+ + SO2 + 2H2O[pic] 2Fe2+ + SO42- + 4H+
Ques: What is Oleum and How is it forms? (1 Mark)
Ans: Oleum is H2S2O7. It forms during the preparation of sulphuric acid, as follows:
SO3 + H2SO4 [pic] H2S2O7
sulphur trioxide Oleum
Ques: Why is the bond angle in PH4+ higher than in PH3? (1 Mark)
Ans: Alone pair of electrons is not present in PH4+. But in PH3, the presence oflone pair of electrons repel the bonds giving a smaller bond angle.
Ques: Why does PCl3 fume in atmosphere? (1 Mark)
Ans: PCl3 fumes in atmosphere due to its hydrolysis in the presence of moisture in atmosphere.
PCl3 + 3H2O [pic] H3PO3 + 3HCl
Ques: What happens when H3PO3 is heated? (1 Mark)
Ans: H3PO3 when heated, disproportionate to give orthophosphoric acid and phosphine.
4H3PO3[pic] 3H3PO4 + PH3
Ques: Why are noble gases least reactive? (1 Mark)
Ans: Noble gases are least reactive because their valence shells are completely filled or they already have octet configuration, which gives them the maximum stability.
Ques: Why is the ionization energy of group 15 elements higher than that of group 14 elements? (1 Mark)
Ans: The ionization energy of group 15 elements is higher than that of group 14 elements because the elements of group 15 have extra stable half-filled p orbital configuration and their size is smaller due to the higher nuclear charge.
Ques: Why does the tendency to exhibit the -3 oxidation state decreases down the group for group 15 elements? (1 Mark)
Ans: The tendency to exhibit -3 oxidation state decreases down the group because of the increase in atomic radii and metallic character down the group.
Ques: Why does basicity decrease form NH3 to BiH3? (1 Mark)
Ans: Basicity decreases from NH3 to BiH3 because as the size of atom increases the electron density decreases and the tendency to donate electrons decreases.Thus, the basic character decreases from NH3 to BiH3.
Ques: Why does NH3 has higher boiling point than PH3? (1 Mark)
Ans: NH3 has higher boiling point than PH3 because of the presence of inter molecular hydrogen bonding in NH3, as the electronegativity difference is quite high in case of Nand H.
Ans: Thermal decomposition of ammonium dichromate:
(NH4)2Cr2O7[pic]N2 + 4H2O + Cr2O3
Ques: How does NH3 behaves as a Lewis base? (1 Mark)
Ans: N in NH3 has a lone pair of electrons that can be donated to form linkage with the metal ions and hence NH3 acts as Lewis base.
Ques: Why is SF6 exceptionally stable? (1 Mark)
Ans: In SF6, the six F atoms protect the central sulphur atom and does not allow any reagent to attack the S atom, thus making the compound extra stable. It is due to the small size of F atom.
Ques: Which aerosols deplete ozone? (1 Mark)
Ans: Freons in aerosol sprays and refrigerants deplete ozone.
Ques: Fluorine has a lower electron gain enthalpy than chlorine. Give reason. (1 Mark)
Ans: Due to the small size of fluorine, thereis astrong inter electronic repulsions in the relativelycompact 2p-orbitals of flourine. So the electron gain enthalpy of fluorine is lower than that of chlorine.
Ques: Why are halogens coloured? (1 Mark)
Ans: Halogens are coloured because they absorb radiations in visible region, resulting in the excitation to higher energy level and transmit the remaining light.The colour of that transmitted light is the colour of Halogen.
Ques: All halogens except F exhibit +1, +3, +5 & +7 Oxidation states. Why? (1 Mark)
Ans: F cannot show oxidation states other than -1 because of the lack of d orbitals and its higher electronegativity.Other halogens can show higher oxidation states due the presence of vacant d orbitals.
Ques: HF is liquid at room temperature while other halides are gases. Why?(1 Mark)
Ans: HF is liquid at room temperature due to the presence of hydrogen bonding between Hydrogen and Flourine atoms But no H-bonding is present in other halides so they are gases.
Ques: Acidic strength increases in this order : HF M(g), ΔaH = enthalpy of atomization
M(g) + Δi H -------------> M2+(g), ΔiH = ionization enthalpy
M2+(g) + aq -------------> M2+(aq) +Δhyd H,ΔhydH = hydration enthalpy
Copper has high enthalpy of atomization and low enthalpy of hydration so E0 (Cu2+ / Cu) is positive.
26 (Q.) Calculate the “spin only” magnetic moment of M2+(aq) ion (Z= 27). (2 Marks)
(Ans) Electronic configuration of M atom is 1s22s22p63s23p63d74s2. It has three unpaired electrons in d orbitals. Magnetic moment = √ n(n+2) BM
= √3 (3+2)
= √15 [pic]3.87 BM
27 (Q.) How does +2 oxidation state becomes more and more stable in the first half of the first row transition elements with increasing atomic number? (2 Marks)
(Ans) The sum of first and second ionization enthalpies increases with increasing atomic number so the standard reduction potentials become less and less negative. Hence the +2 oxidation state becomes more and more stable.
UNIT-9
COORDINATION COMPOUNDS 3 marks
1. Write the formula for the following: - (3)
(i) Tetrahydroxozincate (II)ion
(ii) Hexaammineplatinum (IV) ion
(iii) Hexaamminecobalt (III) sulphate
Ans: (i) [Zn(OH)4]2-
(ii) [Pt(NH3)6]4+
(iii)[Co(NH3)6]2(SO4)3
2. Write the IUPAC name of the following: - (2)
(i)[Pt(NH3)2Cl(NH2CH3)]Cl (ii) [Co(NH3)4Cl(NO2)]Cl
Ans (i) Diamminechloridomethyleamineplatinum (ii) chloride
(ii) Tetraaminechloridonitrito-N-cobalt (iii) chloride
3. What is meant by ambidentate ligands? Give two examples. (1)
Ans : Ligand which can ligate through two different atoms
e.g. CN-, SCN-
4. Explain on the basis of VBT, the experimental findings that [Ni(CN)4]2- ion with a square-planar structure is diamagnetic and the [NiCl4]2- ion with tetrahedral geometry is paramagnetic. (2)
Ans: In [Ni(CN)4]2-
Ni2+ electronic configuration- 3d8
Hybridization - dSP2
Unpaired electron = 0 , therefore it is diamagnetic
In [NiCl4]2-
Ni2+ Electronic configuration 3d8
Hybridization SP3
Unpaired electron = 2, therefore it is paramagnetic
5. Aqueous copper sulphate solution (blue in colour) gives( a) a green precipitate with aqueous potassium fluoride, and(b) a bright green solution with aqueous potassium chloride. Explain. (2)
Ans:
(a) [Cu(H2O)4]2+ + 4F- → [CuF4]2- + 4H2O
Blue green ppt
(b) [Cu(H2O)4]2+ + 4Cl- → [CuCl4]2- + 4H2O
Blue Bright green solution
6. Give a chemical test to distinguish between [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br. What kind of isomerism do they exhibit? (2)
Ans : (i) [Co(NH3)5Br]SO4 + Ba2+ → BaSO4
White ppt
[Co(NH3)5Br]SO4 + Ag+ → No ppt
(ii) [Co(NH3)5SO4]Br. + Ba2+ → No ppt
[Co(NH3)5SO4]Br. + Ag+ → AgBr
Yellow ppt
7. Name the metal present in (i) Chlorophyll (ii) Haemoglobin (iii) Vitamin B12 (iv) Cis-platin (2)
Ans: (i) Mg (ii) Fe (iii) Co (iv) Pt
8. What is the coordination number of central metal ion in (i) [Fe(C2O4)3]3- (ii) [Co(en)2Cl2]+. (1)
Ans: (i) 6 (ii) 6
9. Why are cyclic complexes more stable than open one? (1)
Ans : Cyclic complexes have more stability because of reduced strain in five or six member
rings. e.g. Chlorophyll (cyclic) is more stable than [Co(NH3)5Br]SO4 .
10. CuSO4 on mixing with NH3 (1:4) does not give test for Cu2+ ions but gives test for SO42-
ions. Why? (2)
Ans: It is because when NH3 coordinates to Cu2 ions it forms the complex
[Cu(NH3)4]SO4. Copper ions are present in coordination sphere, therefore, they are
non- ionisable whereas SO42- ions are counter ions which are ionisable.
UNIT-10 MARKS-4
HALOALKANES AND HALOARENES
Q :1 Identify A, B in the following:-
Dry ether H2O
─Br + Mg ─────────→ A ───────→ B 2
Ans: A= ─MgBr B =
Q : 2 Give the IUPAC names of the following:-
(a) Cl CH2 C ≡ C-CH2-Br (b) CH3CH2CH(CH3)CH(C2H5) Cl 2
Ans : A) 1-Bromo,4-Chloro But-2- yne
B) 3-Chloro-4-Methyl-hexane
Q: 3 Explain why Aryl halides are extremely less reactive towards nucleophlic substitution 1
reactions.
Ans : due to resonance in aryl halide in C-X bond will acquire double bond character so
difficult to substitute halogen.
Q: 4 Haloalkanes are only very slightly soluble in water explain. 1
Ans: Unable to form Hydrogen bond with water.
Q : 5 Write short notes on:- (a) Wurtz reaction (b) Swarts reaction 2
Dry Ether
Ans :A) R-X + 2Na +R-X ------------( R-R + 2Na X
B) R-Br + AgF -----------( RF + AgBr
Q : 6 Arrange the following in increasing order of the property indicated 1
Bromomethane, Bromoform, Chloromethane, Dibromomethane ( boiling point)
Ans : Chloromethane < Bromomethane < Dibromomethane < Bromoform .
Q : 7 What do you mean by asymmetric carbon? Give one example. 1
Ans: If all the four atom or group of atoms attach to a carbon are different then carbon is called
asymmetric carbon. e.g. CH3CHBrCl.
Q : 8 Explain why H2SO4 is not used during the reaction of alcohol with KI. 1
Ans: Because HI produced get oxidize to Iodine in presence of Sulphuric acid.
Q : 9 Explain why Reaction of CH3Br with KCN yields CH3CN while with AgCN yields CH3NC? 1
Ans: Because CN- is an ambidentate nucleophile.
Q : 10 Write short notes on:- (a) Sandmeyer’s reaction (b) Finkelstein reaction 2
CuCl /HCl
Ans : (a) C6H5N2Cl ---------------( C6H5Cl
Acetone
(b) C6H5 Br + NaI ----------------( C6H5 I + Na Br
Q : 11Convert : -propane-1-ol to 2-iodopropane. 1
Conc. H2SO4 HI , M.Rule
Ans : CH3 CH2 CH2 OH ----------------( CH3 CH=CH2 ----------------( CH3 CH I CH 3
443K
Q : 12 Arrange the following in increasing order of the property indicated 2
(a) 1-Bromobutane, 2-Bromobutane, 2-Bromo-2-methylpropane ( boiling point)
Ans : 2-Bromo-2-methylpropane CH3-O-C(CH3)3 + NaBr
Q : 2 Give reasons: 2
a. Ethanol has higher boiling point in comparison to methoxymethane .
Ans : Due to presence of intermolecular hydrogenbond in ethanol.
b. Phenols are more acidic than alcohols.
Ans : Due to –R effect of phenoxide ion produced after the loss of proton from phenol, phenoxide ion is more stable than alkoxide ion
Q : 3 (a) o-nitrophenol is steam volatile while p-nitrophenol not.
Ans : Due to presence of intramolecular hydrogen bond
(b)Cleavage of phenyl alkyl ether with HI always gives phenol and alkyl iodide
Ans : Due to resonance C-O bond of phenyl will acquire double bond character hence
difficult to break 2
Q : 4 How are the following conversions carried out: -
a. Methyl magnesium bromide to 2-methylpropane-2-ol
CH3COCH3 H+/H2O
Ans : CH3MgBr ----------------------( (CH3)3C-OMgBr -----------------((CH3)3C-OH
Dry Ether
a. Propene to propan-2-ol
HBr,M.Rule aq.KOH, ∆
Ans : CH3CH=CH2-------------------( CH3CHBrCH3------------------( CH3CHOHCH3
b. Propan-2-one to 2-methyl-2-propanol
CH3MgBr H+/H2O
Ans : CH3COCH3 ---------------------( (CH3)3C-OMgBr -----------------((CH3)3C-OH
Dry Ether 2
Q : 5 Write IUPAC name-
i. CH3-O-CH2-CH-CH3 ii. CH3-CH-CH-CH2-CH2OH
| | |
CH3 Cl CH3
Ans: i) 2-methoxybutane
ii) 4-Chloro,3-methyl butan-1-ol. 2
Q : 6 Arrange the following as property indicated: -
(i) pentan-1-ol, pentanal, ethoxyethane (increasing order of boiling point)
Ans : n-butane C=O group into >CH2
group.
Ans: Clemmensen reduction and Wolff-Kishner reduction
UNIT-13 MARKS-4
Amines
Types of Amines
[pic]
Preparation of amines
1. Reduction method:
[pic]
2. Hoffman’s ammonolysis method:
[pic]
[pic]
3. Reduction of nitriles:
[pic]
4. Reduction of amides:
[pic]
5. Gabriel Phthalimide Synthesis:
[pic]
6. Hoffman’s Degradation Reaction:
[pic]
Physical Properties
Amines are polar in nature and can form H-bonding therefore there boiling pt. is more than non-polar molecules but lower than alcohols and carboxylic acids having same molecular mass.
Lower Amines are soluble in water but solubility decreases with increase in alkyle group.
Methyl and ethyl amines have ammonical smell other have fishy order.
Amines are basic in nature due to presence of lone pair of electrons e.g
[pic]
Amines
(Q.) Why are benzenediazonium salts soluble in water? (1 Mark)
(Ans) Benzenediazonium salts are soluble in water because they are ionic in nature.
(Q.) What are aromatic nitro compounds? (1 Mark)
(Ans) Nitro compounds in which one or more benzene rings are present are called aromatic nitro compounds.
(Q.) Draw the structure of trimethyl phenyl ammonium bromide. (1 Mark)
(Ans) C6H5N(CH3)3Br
(Q.) What is diazotization? (1 Mark)
(Ans) The reaction in which benzendiazonium chloride is prepared by the reaction of aniline with nitrous acid at 273-278K is called diazotization reaction.
(Q.) Why do nitro compounds have higher boiling points than the hydrocarbons having almost same molecular mass? (1 Mark)
(Ans) Nitro compounds have large dipole moments and higher polarity. So, they have higher boiling point than hydrocarbons having almost same molecular mass.
(Q.) How will you convert the acetonitrile to propionitrile? (1 Mark)
(Ans) CH3CN [pic]CH3CONH2[pic]CH3COOH + NH3
Acetonitrile Ethanamide Acetic acid
CH3COOH [pic]CH3CH2OH [pic]CH3CH2Br [pic]CH3CH2CN
Ethanol BromoethanePropionitrile
(Q.) Why primary amines have higher boiling point than tertiary amines? (1 Mark)
(Ans) Because the molecules of primary amines are joint by intermolecular H-bonding while molecules of tertiary amines are joint by weak van der Waals forces.
(Q.) Why aniline does not undergo Friedel Crafts reaction? (1 Mark)
(Ans) In Friedel crafts reaction AlCl3 is used as the catalyst with which anilines give salts. so the reaction is not possible foraniline
(Q.) How is the basic strength of aromatic amines affected by the presence of electron releasing group on the benzene ring? (1 Mark)
(Ans) An electron releasing group increases the electron density on the N-atom. So, its tendency to donate an electron pair to a proton increases and hence the basicity of the amine.
(Q.) What for quaternary ammonium salts are widely used? (1 Mark)
(Ans) The quaternary ammonium salts are used as detergents.
(Q.) Which is more basic CH3NH2 or (CH3)3N? (1 Mark)
(Ans) CH3NH2 is more basic than (CH3)3N due to greater stability of conjugate acid due to H-bonding.
(Q.) Write the short note on reductive amination reactions? (2 Marks)
(Ans) When aldehydes or ketones react with ammonia imines is formed. These imines give the primary amine by catalytic reduction.
RCHO + NH3[pic]RCH=NH [pic]RCH2NH2
Aldehyde imines Primary amine
(Q.) What is the difference between the nitrite (-O-N-O) group and nitro (NO2) group?(2 Marks)
(Ans)
|Nitrite (-O-N-O) group |Nitro (NO2) group |
|1. Nitrite group attaches itself to an alkyl or aryl group |1. Nitro group attaches itself to any alkyl or aryl group through N atom. |
|through oxygen atom. |2. Nitrogen is pentavalent in nitro group. |
|2. Nitrogen is trivalent in nitrite group. | |
(Q.) Why is NO2 group called an ambident group? (2 Marks)
(Ans) Nitro group can attach itself through two different atoms, i.e., through O atom and N atom. Thus, nitro group is an ambident group
(Q.) How will you differentiate in between primary, secondary and tertiary amines? (2 Marks)
(Ans) We can differentiate primary, secondary and tertiary amines by ‘Hinsberg test’. When amines are treated with benzene sulphonyl chloride, the following changes occur: -
(i) Primary amines form monoalkyl benzene sulphonamide, which is soluble in KOH.
RNH2 + C6H5SO2Cl [pic]C6H5SO2NHR [pic] C6H5SO2NKR
Primary Benzene sulphonyl Monoalkyl Potassium salt of Monoalkyl
Amine Chloride sulphonamide sulphonamide
(ii) Secondary amines form dialkyl benzene sulphonamide, which is insoluble in KOH.
R2NH + C6H5SO2Cl [pic]C6H5SO2NR2[pic]insoluble
dialkyl
sulphonamide
(iii) Tertiary amine does not react.
Q.) How will you form quaternary ammonium salt from haloalkane? (2 Marks)
(Ans) When haloalkanes heated with an ethanolic solution of ammonia in a sealed tube at 1000C .
RX + NH3[pic]RNH2[pic]R2NH [pic]R3N [pic]R4+NX-
Haloalkane P. amine S. amine T. amine Quaternary
Ammonium salt
(Q.)What happens when diazoniumfluoroborate is heated with aqueous sodium nitrite solution in the presence of copper?
Give reactions. (2 Marks)
(Ans) In this reaction thediazonium group is replaced by nitro group.
C6H5N2BF4 + NaNO2 + Cu[pic]C6H5NO2 + N2 + NaBF4
(Q.) Why is aniline a weaker base than methylamine? (2 Marks)
(Ans) Aniline and methylamine both have nitrogen with lone pair of electron. In aniline the phenyl group is electron attracting. It tend to decrease the electron density on nitrogen atom and hence decreases electron releasing tendency of nitrogen. While in methylamine CH3- group is electron repelling in nature. It tends to increase the electron density on the nitrogen atom and helps in electron releasing tendency of nitrogen. So, the aniline is a weaker base than methylamine.
[pic]
(Q.) Arrange the following in increasing order of basic strength: -
(i) Triethylamine, ethylamine and ammonia.
(ii) p-nitroaniline, aniline and p-toludine. (2 Marks)
(Ans) (i) Ammonia Cx(H2O)y + x O2
(Q.) Define Monosaccharides? (1 Mark)
(Ans) These are the simplest carbohydrates which cannot be hydrolysed to smaller molecules. Their general formula is (CH2O)n, where n = 3-7.
(Q.) Define the term Oligosaccharides? (1 Mark)
(Ans) Those carbohydrates which give 2-10 molecules of monosaccharides in hydrolysis.
(Q.) Define Disaccharides? (1 Mark)
(Ans) Carbohydrates which on hydrolysis give two molecules of the same or different monosaccharides are called disaccharides. e.g.,
C12H22O11 + H2O [pic]C6H12O6 + C6H12O6
sucrose glucose fructoes
(Q.) What is difference between Reducing and non-reducing sugars or carbohydrates?(1 Mark)
(Ans) All those carbohydrates which contain aldehydic and ketonic group in the hemiacetal or hemiketal form and reduce Tollen’s reagent or Fehling’s solution are called reducing carbohydrates while others which do not reduce these reagents are called non-reducing reagents.
(Q.) Explain the term mutarotation? (1 Mark)
(Ans) Mutarotation is the change in the specific rotation of an optically active compound with time, to an equilibrium mixture.
(Q.) Define glycosidic linkage? (1 Mark)
(Ans) The two monosaccharide units are joined together through an ethereal or oxide linkage formed by the loss of a molecule of H2O. Such a linkage between two monosaccharide units through oxygen atoms is called glycosidic linkage.
(Q.) Give a chemical equation for obtaining Maltose? (1 Mark)
(Ans) Maltose is obtained by partial hydrolysis of starch by the enzyme diastase present in malt i.e., sprouted barley seeds.
2(C6H10O5)n + n H2O [pic]n C6H12O6
(Q.) What are the main sources of vitamins? (1 Mark)
(Ans) The main sources of vitamins are milk, butter, cheese, fruits, green vegetables, meat, fish, eggs, etc.
(Q.) Give two methods for the preparation of glucose? (2 Marks)
(Ans) The methods for the preparation of glucose are:
(i) From sucrose (Cane Sugar).
When sucrose is hydrolysed by boiling with dil. HCl or H2SO4 in alcoholic solution, an equimolar mixture of glucose or fructose is obtained.
C12H22O11 + H2O [pic]C6H12O6 + C6H12O6
(ii) From starch.
Commercially glucose is obtained by hydrolysis of starch by boiling it with dil. H2SO4 at 393 K under pressure.
(C6H10O5)n + n H2O [pic]n C6H12O6
(Q.) Define Carbohydrates? Give their basic classification depending upon their behaviour towards hydrolysis. (2 Marks)
(Ans) Carbohydrates are defined as optically active polyhydroxy aldehydes or polyhydroxy ketone
substances which give these on hydrolysis.
These are broadly classified as:
(i) Monosaccharides.
(ii) Oligosaccharides.
(iii) Polysaccharides.
(Q.) What is Milk sugar? Give its characteristics. (2 Marks)
(Ans) Lactose occurs in milk so, it is called milk sugar. Lactose on hydrolysis with dilute acids yields an equimolar mixture of D-glucose and D-galactose. It is a reducing sugar since it forms an osazone. It undergoes mutarotation and also reduces Tollen’s or Fehling’s solution.
(Q.) Define the term vitamins? State its importance. (2 Marks)
(Ans) Vitamins may be defined as group of bio-molecules (other than fats, carbohydrates and proteins) which are required in small amounts for normal metabolic processes and for the life, growth and health of human beings and animal organisms.Vitamins neither supply energy nor help in building tissues of the cells. They play an important role in keeping good health of human beings and animals. Their deficiency causes serious disturbances and diseases in the body.
(Q.) What do you understand by denaturation of proteins? (2 Marks)
(Ans) When a protein in its native form, is subjected to physical change like in temperature or chemical change like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity. This is called denaturation of protein.
(Q.) Give the D and L configurations of Glyceraldehyde? (2 Marks)
(Ans)
[pic]
(Q.) Give the chemical structure of sucrose & explain why sucrose is non reducing sugar.(2 Marks)
(Ans)
[pic]
The two monosaccharide are held together by a glycosidic linkage between C1 of[pic]-glucose and C2 of[pic]-fructose. Since the reducing groups of glucose and fructose are involved in glycosidic bond formation, sucrose is a non-reducing sugar.
(Q.) Give a broad classification of vitamins? (2 Marks)
(Ans) Vitamins are complex organic molecules.They can be broadly classified as:
(i) Water soluble vitamins: These include vitamin B-complex and vitamin C.
(ii) Fat soluble vitamins: These are oily substances that are not readily soluble in water. However, they are soluble in fat. These include vitamins A,D,E and K. Nucleic acids are bipolar (i.e. polymers present in the living system). They are also called polynucleotides since the repeating structural unit of nucleic acids is a nucleotide.
General structure of a nucleotide can be given as:
[pic]
(Q.) Write a short note on cellulose and give its chemical structure.(3 Marks)
(Ans)
[pic]
Cellulose occurs exclusively in plants and it is the most abundant organic substance in plant kingdom. It is a predominant constituent of cell wall of plant cells. Cellulose is a straight chain polysaccharide composed only of [pic]-D-glucose units which are joined by glycosidic linkage between C1 of one glucose unit and C4 of t he next glucose unit.
(Q.) Give a short note on Zwitter ion? (3 Marks)
(Ans) Amino acids are usually colourless, crystalline solids. These are water soluble , high melting solids and behave like salts rather than simple amines or carboxylic acids. This behaviour is due to the presence of both acidic (carboxylic group) and basic (amino group) groups in the same molecule. In aqueous solution, the carboxyl group can lose a proton and amino group can accept a proton, giving rise to a dipolar ion known as zwitter ion.
[pic]
(Q.) How are peptides formed. Show the formation of peptide bond with diagram. (3 Marks)
(Ans) Peptides are amides formed by the condensation of amino group of one [pic]-amino acid with the carboxyl group of another molecule of the same or different [pic]-amino acid with the elimination of awater molecule. They are classified as di-, tri-, tetra-, etc.
E.g.
[pic]
UNIT-15 MARKS-3
POLYMERS
|POLYMER |MONOMER(Name & Structure) |USES |
|Addition or Chain Growth Polymer |
|Polythene |Ethene CH2=CH2 |Insulator, ,Packing material, |
|Teflon |Tetrfluoroethene CF2=CF2 |Lubricant, Insulator and making non-stick cooking ware. |
|(Poly tetrfluoroethene) | | |
|Poly acrylonitrile |Acrylonitrile CH2=CH-CN |For syntheticfibres and synthetic wool. |
|Buna S |Buta-1,3-diene + Styrene |Automobile tyres and Foot wears |
| |CH2=CH-CH=CH2 C6H5CH=CH2 | |
|Buna N |Buta-1,3-diene + Acrylonitrile |Oil seals, Tank lining |
| |CH2=CH-CH=CH2 CH2=CH-CN | |
|Natural Rubber |2-Methylbuta-1,3-diene (Isoprene) |Used for tyres after vulcanisation |
|Synthetic Rubber(Neoprene) |2-Chlorobuta-1,3-diene (Chloroprene) |Insulator, making conveyor belts and printing rollers |
|Polypropene |Propene CH3-CH=CH2 |Ropes, toys,pipes and fibres |
|Polystyrene |Styrene C6H5CH=CH2 |Insulator, Wrapping material,toys, Radio and television |
| | |cabinets. |
|Polyvinyl chloride |Vinyl Chloride CH2=CH-Cl |Rain coats, Hand bags, Vinyl flooring and water pipe. |
|(PVC) | | |
|Condensation or Step Growth Polymers |
|Terylene(Dacron) |Ethane-1,2-diol + Benzene-1,4-dicarboxylic acid |Used for making fibres, safety belts, tents |
|Nylon 66 |Hexamethylenediamine + Adipic acid |For making brushes,paratutes and ropes |
| |NH2(CH2)6NH2 HOOC(CH2)4COOH | |
|Nylon 6 |Caprolactum |Tyrescords,fabrics andropes |
|Bakelite |Phenol + Methanal |Combs,electricalswitches,handles of utensiles and |
| | |computer discs |
|Melamine |Melamine + Methanal |Unbreakable crockery |
|PHBV (biodegradable) |3-Hydroxybutanoic acid + |Specialty packaging, orthopedic devices, In controlled |
| |3-Hydroxypentanoic acid |drug release |
|Nylon 2 – Nylon 6 |Glycine + Amino caproic acid | |
|(biodegradable) |H2N-CH2-COOH H2N (CH2)5-COOH | |
|Urea-formaldehyde resin |Urea + Formaldehyde |Unbreakable cups , laminated sheet |
|Glyptal |Ethane1,2-diol + Benzene-1,2-dicarboxylic acid |Binding material |
| | |in preparation of mixed plastics and paints |
|****************************************************************************************** |
|Semi-synthetic poly |Cellulose Acetate (Rayon) |
|Thermoplastic polymers |Linear or slightly branched / capable of repeatedly softening on heating and hardening on cooling. Example : |
| |Polythene, Polystyrene, Polyvinyls, etc. |
|Thermosetting polymers |Cross linked or heavily branched molecules, / on heating undergo extensive cross linking in moulds and again |
| |become infusible. These cannot be reused. Examples : Bakelite, Urea-formaldelyde resins. |
|Homo-polymer & |Homo-polymer (Polymer of a single monomeric species. Example : Polythene , PVC |
|Co-polymer |Co-polymer( Polymer of more than one monomer .Example : Nylon66, Bakelite |
|Initiators |Benzoyl Peroxide [ C6H5CO-O-O-CO-C6H5 ] (in freeradical addition polymerization) |
|Vulcanisation of Rubber. |Natural rubber is soft at high temp and brittle at low tempand absorbs water. To improve these physical |
| |properties, it is heated with sulphur and an appropriate additive at a temperature range between 373 K to 415 |
| |K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets |
| |stiffened. |
Polymers
(Q.) Give the structure of natural rubber? (1 Mark)
(Ans)
[pic]
(Q.) Define the term polymerization? (1 Mark)
(Ans) The repeating structural units formed from some simple and reactive molecules (monomers) are linked together by covalent bonds. This process of formation of polymers from their respective monomers is called polymerization.
(Q.) Define Elastomers? (1 Mark)
(Ans) Elastomers are rubber-like solids with elastic properties. In elastomers, the polymer chain is heldtogether by weak intermolecular forces which allow the polymer to be stretched.
e.g. buna-S, buna-N neoprene.
(Q.) What are fibers? (1 Mark)
(Ans) Fibers are the thread forming solids which possess high tensile strength and high modulus. These polymers possess strong intermolecular forces.Thus leading to close packing of chains and imparting crystalline nature. e.g., polyamides( nylon 6,6) and polyesters( terylene), etc.
(Q.) Define Thermoplastics polymers? (1 Mark)
(Ans) Thermoplastic polymers are the linear or slightly branched chain molecules capable of repeatedly softening on heating and hardening on cooling. Some examples of thermoplastics are polythene, polystyrene, polyvinyl, etc
(Q.) Define Thermosetting plastics? (1 Mark)
(Ans) Thermosetting polymers are cross linked or heavily branched molecules which on heating undergo extensive cross linking in moulds and again become infusible. Some examples of thermosetting plastics are bakelite, urea-formaldehyde resins, etc.
(Q.) Give the method of preparation of polyacrylonitrile? (2 Marks)
(Ans) The addition polymerization of acrylonitrile in presence of a peroxide catalyst leads to the formation of polyacrylonitrile. It is used as a substitute for wool in making fibers as orlon or acrilan.
[pic]
(Q.) Define copolymerization? Give chemical reaction showing formation of copolymer.(2 Marks)
(Ans) Copolymerisation is a polymerization reaction in which a mixture of more than one monomeric species is allowed to polymerise and form a copolymer. For example, a mixture of a 1,3 – butadiene and styrene form a copolymer.
[pic]
(Q.) Describe the method for the preparation of neoprene? (2 Marks)
(Ans) Neoprene or poly chloroprene is formed by the free radical polymerization of chloroprene.
[pic]
(Q.) Differentiate between Addition and Condensation polymers? (2 Marks)
(Ans)
|S.No |Addition Polymers |Condensation polymers |
|1. |They are formed by the repeated addition of |They are formed by repeated condensation reaction between two different |
| |molecules possessing double or triple bonds. |bi-functional and tri-functional monomeric units. |
|2. |E.g. polythene |E.g. nylon 66 |
(Q.) Differentiate between Homopolymers and Copolymers with example. (2 Marks)
(Ans) Homopolymers: The addition polymers formed by the repeated addition of monomer molecules possessing double or triple bonds, are known as homopolymers.
E.g., nCH2 = CH2----->---(CH2—CH2)---
Ethene polythene
Copolymers: The polymers formed by addition polymerization of two different monomers are termed as copolymers.
E.g., nCH2 = CH—CH = CH2 + nC6H5CH=CH2---->---[CH2—CH = CH—CH2—CH2—CH(C6H5)]n---
(Q.) Give the differences between homopolymers and copolymers? (2 Marks)
(Ans)
|S.No. |Homopolymers |Copolymers |
|1 |The addition polymers formed by the polymerisation of a single |The polymers formed by the addition polymerisation of two |
| |monomeric unit are called Homopolymers. |different monomers are termed as copolymers. |
|2 |E.g. Polythene. |E.g. Buna-S |
(Q.) What is synthetic rubber? (2 Marks)
(Ans) Synthetic rubber is any vulcanisable rubber like polymer, which is capable of getting stretched twice its length. However, it returns to its original shape and size as soon as the external stretching force is released.
(Q.) Give the method of preparation of Teflon and its uses. (3 Marks)
(Ans) Polytetrafluoroethene (Teflon) is manufactured by heating tetrafluroethene with a free radical or persulphate catalyst at high temperature. It is chemically inert in nature. It is used for making oil seals and gaskets and also used for non-stick surface coated utensils.
[pic]
Tetraflouroethane Teflon
(Q.) What are the different types of structural polymers?Give examples? (3 Marks)
(Ans) There are three different types of structural polymers:
(1) Linear polymers: These polymers consist of long and straight chains.
e.g. polythene,polyvinyl chloride, etc.
(2) Branched chain polymers: These polymers contain linear chains having some branches.
e.g. low density polythene.
(3) Cross linked polymers (network polymers): These are usually formed from bi-functional and tri-functional monomers and contain strong covalent bonds between various linear polymer chains.
e.g. bakelite, melamine etc.
(Q.) Give the method for preparing Bakelite? (3 Marks)
(Ans) Bakelite is manufactured from Phenol-formaldehyde polymers. It is obtained by the condensation reaction of phenol with formaldehyde in thepresence of an acid or base catalyst. The initial product formed is a linear chain called – Novolac used in paints. Novolac on heating with formaldehyde undergoes cross linking to form infusible solid mass called bakelite.
[pic]
(Q.) Give the method of preparation and uses of nylon 6? (3 Marks)
(Ans) Nylon 6 is obtained by heating caprolactum with water at high temperature.
[pic]
Nylon 6 is used for the manufacture of tyre cords, and fabrics and ropes.
(Q.) How are condensation polymers formed? Explain giving one example. (3 Marks)
(Ans) The condensation polymers are formed by repeated condensation reaction between two different bi-functional or tri-functional monomeric units. During this process, a small molecule of water, alcohol, hydrogen chloride, etc is eliminated. E.g. terylene, nylon 6,6, nylon 6, etc.
Preparation of nylon 6,6:
nH2N(CH2)6NH2 + nHOOC(CH2)4COOH ----->---(NH(CH2)6NHCO(CH2)4CO)n--- + n H2O
(Q.) What are natural and synthetic polymers? Give 2 examples of each. (3 Marks)
(Ans) Natural polymers: Polymers which are found in plants and animals are called natural polymers. e.g. proteins, cellulose starch etc.
Synthetic polymers: Man made polymers are called synthetic polymers. They consists of a number of smaller molecules to form large molecules. e.g. nylon 6,6 and Buna-S.
(Q.) Define the term polyesters? How is it manufactured? (3 Marks)
(Ans) Polyesters are the condensation products of dicarboxylic acids and diols. e.g. Dacron or Terylene.
It is manufactured by heating a mixture of ethylene glycol and terephthalic acid at 420 to 460 K in the presence of zinc acetate-antimony trioxide catalyst.
(Q.) Explainvulcanisation of rubber? (3 Marks)
(Ans) Natural rubber becomes soft at high temperatures and brittle at low temperatures. It has a high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidizing agents.
To improve upon these physical properties, the process of vulcanization is carried out. It consists of heating a mixture of raw rubber with sulphur with a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at reactive sites of double bonds and thus the rubber gets stiffened.
(Q.) Give three examples of biodegradable polymers? (3 Marks)
(Ans) (1) phbv
(2) Nylon-2
(3) nylon-6
UNIT-16 MARKS-3
CHEMISTRY IN EVERYDAY LIFE
|THERAPEUTIC ACTION OF DIFFERENT DRUGS |
|Drugs |Action |Example |
|Analgesics |Relieving pain |AspirinAnalgin, Seridon, Anacine, |
|Analgesics |Reduce tension and pain. produceunconsciouness. |Opium, Heroin , Pethidine , Codeine, Morphine |
|(Narcotic ) | | |
|Antibiotics | Produced by micro – organism, that can inhibit the |Penicillin G(Narrow Spectrum) |
| |growth or destroy other micro-organism. |Streptomycin, Ampicillin ,Amoxycillin Chloramphenicol Vancomycin, |
| | |ofloxacin, |
|Antiseptics |Prevent the growth of micro-organism or kill them but | Dettol, Bithional(in soap) |
| |not harmful to the living tissues. |Tincture iodine, 0.2% phenol, |
|Disinfectants |Kills micro-organisms, not safe for living tissues. | 1% phenol, |
| |It is used for toilets, instruments. |chlorine (Cl2) , |
| | |Sulphurdioxide ( SO2) |
|Antacids |Reduce or neutralise the acidity. |[pic] |
|Antihistamines |Reduce release of acid. |Cimetidine(Tegamet), Ranitidine (Zantac), |
| | | |
| |It is also used to treat allergy |Brompheniramine ( Dimetapp) |
| | |Terfenadine ( Seldane) |
|Tranquilizers |Reduce the mental anxiety, stress, (sleeping pill) |Valium, Serotonin, Veronal, Equanil,Amytal,Nembutal,Luminal, Seconal |
|Antipyretics |Reduce body temperature |Aspirin, Paracetamol, Analgin, Phenacetin. |
|Antifertility |These are the steroids used to control the pregnancy |Norethindrone, Ethynylestradiol (novestrol ) |
|drugs | | |
|CHEMICALS IN FOOD |
|Sweetening Agent |Saccharine,Aspartme(for cold foods) Alitame |
| |Sucrolose(stable at cooking temp) |
|Food Preservative |Salt, sugar, veg. oils, sodium benzoate |
|CLEANSING AGENTS |
|Soap |Na / K –salt of long chain fatty acids |Not work in hard water becoz with Ca and Mg salt soap produce insoluble |
| | |scum |
|Anaionicdetergen |Sodium laurylsulphate |Used in household work / in tooth paste |
|Cationic detergent |Cetyltrimethyl ammonium bromide |Hair conditioner / germicidal properties |
|Non ionic detergent |Ester of searic acid and polyethylene glycol |Liquid dishwashing |
|Detergents with highly branched hydrocarbon parts are non biodegradable and hence water pollutants so branching is minimized which are degradable and pollution is|
|prevented. |
Chemistry in Everyday Life
(Q.) Why it is advised to consult a doctor before taking a sleeping drug? (1 Mark)
(Ans) Because itmay produce harmful effects and can act as a poison and cause even death.
(Q.) Give the name of the alkoloids which are used to cure Hypertension and Malaria.(1 Mark)
(Ans) Alkoloid for hypertension is reserpine and for malaria is quinine.
(Q.) Name the macromolecules which are chosen as drug targets. (1 Mark)
(Ans) Macromolecules like proteins, nucleic acid, carbohydrates and lipids are chosen as drug targets.
(Q.) What do you understand by chemotherapy? (1 Mark)
(Ans) It is the branch of chemistry deals with the study of the treatment of the diseases using chemicals.
(Q.) Name the forces which are involved in holding the drugs to the active site of the enzymes? (1 Mark)
(Ans) Hydrogen bonding, ionic bonding, dipole-dipole interactions or van der Waals interactions.
(Q.) Antacids and antiallergic drugs interfere with the function of histamines but why do these not interfere with the function of each other? (1 Mark)
(Ans) Because the antiallergic and antacids drugs work on different receptors, so antihistamines remove allergy and antacid remove acidity.
(Q.) Give a name of the substance which can be used as antiseptic and disinfectant.(1 Mark)
(Ans) 0.2% solution of phenol acts as antiseptic and 1% solution of it act as disinfectant.
(Q.) What are the main constituents of dettol? (1 Mark)
(Ans) Chloroxylenol and terpineol in a suitable solvent.
(Q.) What is tincture iodine? Give one of its use. (1 Mark)
(Ans) The 2-3% solution of iodine in alcohol and water is tincture iodine. It is used as an antiseptic for wounds.
(Q.) Why is the aspartame used only for the cold foods and the drinks? (1 Mark)
(Ans) Aspartame decomposes at baking or cooking temperature.so it isusedonlyin cold drinks and cold foods.
(Q.) What are artificial sweetening agents? Give examples. (1 Mark)
(Ans) The chemical substances which are sweet in taste but do not add any calorie to our body are called artificial sweetening agents. For example Saccharin and Aspartame.
(Q.) Why alitame is not used as an artificial sweetening agent? (1 Mark)
(Ans) Because it is a high potency artificial sweetener.
(Q.) Why detergents are called soapless soaps? (1 Mark)
(Ans) Because the detergents are cleansing agents which have all the properties of a soap but do not contain any soap.
(Q.) Why do soaps not work in hard water? (1 Mark)
(Ans) In hard water, there are calcium and magnesium salts. So the soaps get precipitated in hard water as calcium and magnesium salts
(Q.) Name the antibiotic used for typhoid fever. (1 Mark)
(Ans) Chloramphenicol.
(Q.) What are antipyretics? Give some examples. (1 Mark)
(Ans) These are the chemicals used to lower down the temperature during the fever. Example: paracetamol, aspirin etc.
(Q.) Why are detergents preferred over soaps? (1 Mark)
(Ans) Detergents contain calcium and magnesium salts of sulphonic acids which are soluble even in hard water but soaps are not soluble in hard water.
(Q.) Label the hydrophilic and hydrophobic parts in the given molecule.
[pic] (1 Mark)
(Ans)
[pic]
Hydrophobic Hyhrophilic
(Q.) Why the medicines should not be taken without consulting the doctors? (1 Mark)
(Ans) When a drug binds to more than one receptor site it causes side effects. Secondly the dose of the drug is also decisive because higher doses of some drugs act as a poison. So a doctor must be consulted to choose the right drug.
(Q.) Can soaps and detergents be used to check the hardness of water? (1 Mark)
(Ans) Detergents do not get precipitated in water but the soaps get precipitated in hard water as insoluble calcium and magnesium soaps. So soaps can be used to check the hardness of water but detergents not.
(Q.) Give the name and structure of two common antihistamine drugs. (2 Marks)
(Ans)1. Diphenylhydramine:
[pic]
2. Promethazine:
[pic]
(Q.) Explain the following: (i) Equanil (ii) Morphine (2 Marks)
(Ans) (i) Equanil: It possesses a good tranquilizing effect so it is used to cure depression and hypertension.
(ii) Morphine: It is used as analgesic. It is also a habit forming drug.
(Q.) Give structure of following antifertility drugs:a) Mifepristone b) Norethindrone(2 Marks)
(Ans) a) Mifepristone:
[pic]
b)Norethindrone:
[pic]
(Q.) How do antiseptics differ from disinfectants? (2 Marks)
(Ans) Antiseptics are the chemicals which are used to prevent the growth of micro organisms or to kill them but these are not harmful to animal tissues. Examples- Furacin and Soframycin.
Disinfectants are the chemicals which are used to kill micro organisms but these are harmful to the animal tissues. Examples- phenol and chlorine.
(Q.) What do you understand by “board spectrum antibiotics”? (2 Marks)
(Ans) These are effective against several types of bacteria. For example tetracycline, chloramphenicol, Ofloxacinwhichare used as antibiotics.
(Q.) What refers to the statement “Ranitidine is an antacid”? (2 Marks)
(Ans) This statement refers to the classification of the drugs according to the pharmacological effect because any drug used to neutralize the excess acid present in the stomach will be called an antacid.
(Q.) Define the terms Lead compounds and Target molecules. (2 Marks)
(Ans) Lead compounds: The knowledge of the physiological function of the drug target in the body helps us to choose a compound which can interact with the target and hence is expected to be therapeutically active .These compounds are called target compounds.
Target molecules: The macromolecules like carbohydrates, proteins,lipidsetc.interacting with the drugs are called target molecules.
(Q.) Why are cimetidine and ranitidine better antacid than sodium bicarbonate or magnesium or aluminium hydroxide. (2 Marks)
(Ans) If there is an excess use of sodium bicarbonate or aluminium hydroxide or magnesium hydroxide in the stomach,it becomes alkaline and the HCl release in more quantitymay cause ulcers in the stomach. On the other hand cimetidine and ranitidine prevent the interaction of histamine with the receptor cells in the stomach wall and thus release lesser amount of HCl.
(Q.) Explain the term bactericidal and bacteriostatic drug. (2 Marks)
(Ans) A drug which kills the organisms in the body is called bactericidal drug and a drug which inhibits the growth of organisms is called bacteriostatic drug.
(Q.) Give the name and structure of two antacids. (2 Marks)
(Ans) 1. Omeprazole:
[pic]
2. Lansoprazole:
[pic]
(Q.) What do you understand by (i) Tranquillizers (ii) Antifertility drugs (iii) Antihistamines
Explain with examples. (3 Marks)
(Ans) Tranquillizers: The drugs which act on central nervous system to cure mental diseases are called tranquillizers. Example-Chlordiazepoxide and Meprobamate etc.
Antifertility drugs: The chemicals which are used to check pregnancy in women are called antifertility drugs. Examples- Norethindrone and Mifepristone.
Antihistamines: The drugs which interfere with the natural action of histamine are called antihistamines. Examples- Brompheniramine and Terfenadine.
(Q.) Define the following with examples.(i) Preservatives(ii) Biodegradable detergents
(iii) Non-biodegradate detergents (3 Marks)
(Ans) i) The chemical substances which are used to protect the food against bacteria, yeast, and moulds are known as preservatives. Examples- sodium benzoate, sorbic acid and its salts etc
ii) Biodegradable detergents: The detergents having straight hydrocarbon chains are easily decomposed by micro organisms. Examples- sodium lauryl sulphate, 4-(1-dodyl) benzene sulphonateetc
iii) Non-biodegradable detergents: These contain branched hydrocarbon chains and are not easily decomposed by the micro organisms. Examples- sodium4-(1, 3, 5, 7-tetramethyloctyl) benzenesulphonate.
(Q.) Explain the cleansing action of soaps. (3 Marks)
(Ans) Suppose some grease or oil is sticking on the surface of a cloth, When it comes incontact with the soap solution the stearate ions arrange themselves around it in such a way that hydrophobic parts of the stearate ions are in the oil and the hydrophilic parts project outside the oil droplets. As hydrophilic part is polar so it interacts with the water molecules present around the oil droplet. As a result, the oil droplet is pulled away from the surface of cloth into water to form ionic micelle which is then washed away with the excess of water.
(Q.) Write the chemical equations for preparing sodium soap from glycerol oleate and glycerol palmitate. (3 Marks)
(Ans) Preparation of soap from glycerol palmitate(Saponification):
Heat CH2OH
(C15H31COO)3C3H5 + 3NaOH -------------> | + 3C15H31COONa
(glycerolpalmitate) sodium CHOH sodium palmitate
hydroxide | (soap)
CH2OH
glycerol
Preparation of soap from glycerol oleate (Saponification):
heat CH2OH
(C17H33COO)3C3H5 + 3NaOH -----------> l + 3C17H33COONa
(glycerololeate) CHOH sodium oleate
| (soap)
CH2OH
(Glycerol)
(Q.) Describe the following terms with suitable examples.
a) Anionic detergents b) Cationic detergents c) Neutral detergents. (3 Marks)
(Ans) a) Anionic detergents: The detergents in which a large part of their molecules are anions are called anionic detergents. These are of two types:
i)Sodium alkyl sulphates: example- sodium lauryl sulphate (C11H23CH2OSO3Na).
ii)Sodium alkylbenzenesulphonates: example- sodium 4- (1-dodecyl) benzenesulphonate.
[pic]
b) Cationic detergents: These are quaternary ammonium salts. Example- cetyltrimethylammoniumchloride.
c) Neutral detergents: These are esters of high molecular mass alcohols with fatty acids. Example- polyethylene glycol stearate
{CH3 (CH2)16COO(CH2CH2O)nCH2CH2OH}
(Q.) Name the hydrophobic and hydrophilic parts in the following compounds.
a) CH3(CH2)10CH2OSO3Na b) CH3(CH2)15─N(CH3)Br−
c) CH3(CH2)6COO(CH2CH2O)nCH2CH2OH (3 Marks)
(Ans) (a)CH3(CH2)10CH2 — OSO3Na
hydrophobic hydrophilic
(b)CH3(CH2)15 — N(CH3)Br−
hydrophobic hydrophilic
(c)CH3(CH2)6 — COO(CH2CH2O)nCH2CH2OH
hydrophobic hydrophilic
Important tools / notes for Organic Chemistry (Class XII)
Compiled by N Kar, PGT (Chem) , KV Kunjaban, Agartala
KEY FOR CONVERSIONS IN ORGANIC CHEMISTRY
|S.No |Reagent |Group Out |Group In |Remark |
|1 |KMnO4 / H+ |-CH2OH |-COOH |Strong Oxidation (20 alc( ketone) |
|2 |LiAlH4 |-COOH |-CH2OH |Strong Reduction (ketone ( 20 alc) |
|3 |Cu / 573 K or CrO3 |-CH2OH |-CHO |Dehydrogenation |
|4 |PCl5 or SOCl2 |-OH |-Cl | |
|5 |Cl2 / Δ or Cl2 / UV |-H |-Cl |Free radical substitution |
|6 |Aq NaOH / KOH |-X |-OH |Nucleophilic substitution |
|7 |KCN |-X |-CN |Step Up |
|8 |AgCN |-X |-NC | |
|9 |Alcoholic KOH |-HX |= |Dehydrohalogenation (Stzf) |
|10 |Mg / dry ether | |Mg |R-X ( R-MgX |
|11 |HBr |>=< |H, Br |Merkovnikov |
|12 |H2 / Pd-BaSO4 |-COCl |-CHO |Rosenmund Reduction |
|13 |Zn-Hg / HCl |>C=O |-CH2- |Clemmension Reduction |
|14 |NH3 / Δ |-COOH |-CONH2 |-COOH + NH3 ( -COONH4 |
|15 |Br2 / NaOH or NaOBr |-CONH2 |-NH2 |Step Down ( Hoffmann) |
|16 |HNO2 or NaNO2/HCl |-NH2 |-OH |HONO |
|17 |CHCl3 / alc KOH |-NH2 |-NC |Carbyl amine |
|18 |P2O5 |-CONH2 |-CN |Dehydration |
|19 |H3O+ |-CN |-COOH |Hydrolysis |
|20 |OH- |-CN |-CONH2 | |
|21 |LiAlH4 |-CN |-CH2NH2 |Reduction |
|22 |Red P / Cl2 |α-H of acid |-Cl |HVZ Reaction |
| | In benzene ring |
|23 |Fe / X2 /dark |-H |-X |Halogination |
|24 |CH3Cl / AlCl3(anhyd) |-H |-CH3 |Friedel Craft alkylation |
|25 |CH3COCl / AlCl3(anhyd) |-H |-COCH3 |Friedel Craft acylation |
|26 |Conc.HNO3/con.H2SO4 |-H |-NO2 |Nitration |
|27 |Conc H2SO4 |-H |-SO3H |Sulphonation |
|28 |KMnO4 / H+ |-R |-COOH |Oxidation |
|29 |CrO2Cl2 / H+ |-CH3 |-CHO |Mild oxidation(Etard Reaction) |
|30 |Sn / HCl or Fe/HCl |-NO2 |-NH2 |Reduction |
|31 |NaOH / 623K / 300 atm |-Cl |-OH | |
|32 |Zn dust / Δ |-OH |-H | |
|33 |NaNO2 / dil HCl / 273-278 K |-NH2 |-N2+Cl- |Diazo reaction |
|34 |CuCl / HCl or Cu/HCl |-N2+Cl- |-Cl |Sanmeyer or Gattermann |
|35 |CuBr / HBr or Cu/HBr |-N2+Cl- |-Br |Sanmeyer or Gattermann |
|36 |CuCN / KCN |-N2+Cl- |-CN |Sanmeyer |
|37 |KI |-N2+Cl- |-I | |
|38 |HBF4 / Δ |-N2+Cl- |-F | |
|39 |H3PO2 or CH3CH2OH |-N2+Cl- |-H | |
|40 |H2O / 283 K |-N2+Cl- |-OH | |
|41 |HBF4/ NaNO2, Cu / Δ |-N2+Cl- |-NO2 | |
|42 |C6H5-OH |-N2+Cl- |-N=N-C6H5-OH |Coupling ( p-hydroxy) |
|43 |C6H5-NH2 |-N2+Cl- |-N=N-C6H5-NH2 |Coupling ( p-amino) |
Reactions of Grignard Reagent
|Grignard reagent + |Any one below + H2O ( |Product |
|R-MgX |H2O or ROH or RNH2 |R-H |
| |H-CHO |R-CH2-OH (10 alc) |
| |R-CHO |R-CH(OH)-R (20 alc) |
| |R-CO-R |R2C(OH)-R (30 alc) |
| |CO2 |R-COOH |
| |R-CN |R-CO-R |
| |HCOOR |Aldehyde |
| |RCOOR |Ketone |
NB: i) During reaction generally changes take place in the functional group only so see the functional
group very carefully.
ii) Remember structural formula of all the common organic compounds ( with their IUPAC and common
names)
iii) Wurtz Reaction and Aldol Condensation are not included in the table although they are
very important for conversions so study them .
iv) By taking examples practice all the above cases ( from 1 to 43 and Grignard)
v) Practice only from NCERT book.
vi) Start practicing NOW !
How to use the table? See below.
[pic]
Directional Properties of groups in benzene ring for electrophilic substitution
Ortho-para directing group: -R , -OH, -NH2, -X, -OR, -NHR, -NR2, -NHCOCH3, -CH2Cl, -SH, - Ph
Meta-directing group: -NO2 , -CHO , -COOH , COOR , -CN , -SO3H , -COCH3 , -CCl3 , -NH3+ ,
NAME REACTIONS (ORGANIC CHEMISTRY)
| |Finkelstein |CH3Br + NaI [pic] CH3-I + NaBr |
| |Swarts |CH3Br + AgF [pic] CH3F + AgBr |
| |Friedel-Crafts Alkylation |[pic] |
| |Friedel-Crafts Acylation |[pic] |
| |Wurtz |[pic] |
| |Fittig |[pic] |
| |Wurtz-Fittig |[pic] |
| |Kolbe |[pic] |
| |Reimer-Tiemann |[pic] |
| |Williamson |CH3-Br + CH3-ONa [pic] CH3-O- CH3 + NaBr |
| |Stephen |[pic] |
| |Etard |[pic] |
| |Gatterman – Koch |[pic] |
| |Rosenmund reduction |[pic] |
| |Clemmensen |[pic] |
| |reduction | |
| |Wolff-Kishner reduction |[pic] |
| |Tollens’ test |R-CHO + 2 [Ag(NH3)2]+ + 3 OH- [pic]R-COO- + 2Ag [pic] + 2H2O + 4 NH3 |
| |Fehling’s test |R-CHO + 2 Cu2+ + 5 OH- [pic]R-COO- + Cu2O [pic] + 3H2O |
| |Iodoform Reaction |[pic] |
| |Aldol condensation |[pic] |
| |Cannizzaro |[pic] |
| |Hell-Volhard-Zelinsky (HVZ) |[pic] |
| |Hoffmann bromamide degradation |[pic] |
| |Carbylamine |R-NH2 + CHCl3 + 3 KOH [pic] R-NC + 3 KCl + 3 H2O |
| |Sandmeyer. |[pic] |
| |Gatterman |[pic] |
| |Coupling |[pic] |
ELECTRON DISPLACEMENT EFFECTS
+ I : O- , COO- , (CH3)3C , (CH3)2CH , CH3CH2 , CH3 (electron donating)
- I : NR3+ , SR2+ , NH3+, NO2 , SO2R , CN , COOH , F , Cl , Br , I , OR , OH, NH2 (withdrawing)
+ R ( + M ) : OH , NH2 , OR , NHR , X (electron donating)
- R ( - M ) : NO2 , CN , CHO , COOH , COCH3 (electron withdrawing)
DIRECTIVE INFLUENCE OF SUBSTITUENTS IN BENZENE RING
(for electrophilic substitution reactions)
|EFFECT OF THE GROUP |DIRECTING |ACTIVATING / DEACTIVATING |
|+ I |Ortho / Para |Activating |
|+ I , + R |Ortho / Para |Activating |
|- I < + R |Ortho / Para |Activating |
|- I > + R |Ortho / Para |Deactivating |
|- I |Meta |Deactivating |
|- I , - R |Meta |Deactivating |
Example: - I > + R : - X , - CH=CH2 , -CH=CH-COOH , -CH2-Cl
These groups are deactivating but exceptionally o / p directing due to +E effect by the attacking reagents electron density increases at ortho and para position .
If two groups are present initially
1. When both the groups present in benzene ring are o/p directing than the order of influence :
O- > NH2 > NR2 > OH > OCH3 > NHCOCH3 > CH3 > X
2. When both the groups present in benzene ring are meta directing than the order of influence :
(CH3)3N+ > NO2 > CN > SO3H > CHO > COCH3 > COOH
3. When one group is o/p and another is m – directing than o/p directing group takes priority
IUPAC & Common Names of Some Common Organic Compounds (Aliphatic)
|Sl |IUPAC Name |Formula / Structure | Common Name |
| | | | |
| |Methane | CH4 |Methane |
| |Ethane | CH3-CH3 |Ethane |
| |Propane |CH3-CH2-CH3 |Propane |
| | | | |
| |Ethene |CH2=CH2 |Ethylene |
| |Ethyne |CH≡CH |Acetylene |
| | | | |
| |Chloromethane | CH3Cl |Methyl chloride |
| |Chloroethane |CH3CH2-Cl |Ethyl chloride |
| |Trichloromethane |CHCl3 |Chloroform |
| |Triiodomethane |CHI3 |Iodoform |
| | | | |
| |Methanol | CH3-OH |Methyl alcohol |
| |Ethanol | CH3CH2-OH |Ethyl alcohol |
| |Propanol |CH3CH2CH2-OH |Propyl alcohol |
| |Propan-2-ol |CH3CH(OH)CH3 |Isopropyl alcohol |
| |Ethane-1,2-diol |CH2(OH)-CH2(OH) |Ethylene glycol |
| | | | |
| |Methanal | H-CHO |Formaldehyde |
| |Ethanal | CH3-CHO |Acetaldehyde |
| |Propanal |CH3CH2-CHO |Propionaldehyde |
| | | | |
| |Propanone |CH3-CO-CH3 |Acetone |
| | | | |
| |Methanoic acid | H-COOH |Formic acid |
| |Ethanoic acid | CH3-COOH |Acetic acid |
| |Propanoic acid |CH3CH2-COOH |Propionic acid |
| | | | |
| |Ethanoylchloride |CH3-COCl |Acetyl chloride |
| |Ethanamide | CH3-CONH2 |Acetamide |
| |Ethanoicanhydride |(CH3CO)2O |Acetic anhydride |
| |Methylethanoate |CH3-COOCH3 |Methyl acetate |
| | | | |
| |Methanamine | CH3-NH2 |Methyl amine |
| |Ethanamine |CH3CH2-NH2 |Ethyl amine |
| |N-methylmethanamine |CH3-NH-CH3 |Dimethyl amine |
| |Ethanenitrile |CH3-CN |Methyl cyanide |
| |Methyl magnesium bromide |CH3-MgBr |Methyl magnesium bromide |
[pic]
Distinguish By a Single Chemical Test
1. All aldehydes ( R-CHO) give Tollens’ Test and produce silver mirror.
RCHO + 2 [Ag(NH3)2]+ + 3 OH- ( RCOO- + 2 Ag + 2H2O + 4 NH3
Tollens’ Reagent silver ppt
Note: HCOOH(methanoic acid ) also gives this test, ketones(RCOR) do not give this test
2. All aldehydes (R-CHO) and ketones(RCOR) give 2,4-DNP test
RCOR + 2,4-DNP ( Orange ppt
R-CHO + 2,4-DNP ( Orange ppt
3. Aldehydes and ketones having CH3CO- (keto methyl) group give Iodoform Test. Alcohols having CH3CH- group also give Iodoform Test.
|
OH
CH3CHO + 3I2 + 4 NaOH ( CHI3 + HCOONa + 3 NaI + 3H2O
Yellow ppt
The following compounds give Iodoform Test: ethanol (C2H5OH), propan-2-ol (CH3CH(OH)CH3), ethanal(CH3CHO), propanone(CH3COCH3), butanone ( CH3COCH2CH3) , pentan-2-one (CH3COCH2 CH2CH3) , acetophenone ( PhCOCH3 )
4. All carboxylic acids ( R-COOH) give Bicarbonate Test
RCOOH + NaHCO3 ( RCOONa + CO2 + H2O
effervescence
5. Phenol gives FeCl3 Test
C6H5OH + FeCl3 ( (C6H5O)3Fe + 3 HCl
(neutral) (violet color)
6. All primary amines (R/Ar -NH2) give Carbyl Amine Test
R-NH2 + CHCl3 + KOH(alc) ( R-NC + KCl + H2O
offensive smell
7. Aniline gives Azo Dye Test ( Only for aromatic amines)
C6H5NH2 + NaNO2 + HCl ( C6H5N2+Cl- ; then add β-naphthol ( orange dye
8. All alcohols (ROH) give Na-metal test
R-OH + Na ( R-ONa + H2
bubbles
9. For esters (RCOOR) : Hydrolyses first. Then see the products ( acid & alcohol) and give a test to identify
them
10. All alkenes (C=C) and alkynes (C≡C) decolorizes Br2 – water from red to colorless
11. Lucas Test to distinguish primary, secondary and tertiary alcohols
Lucas reagent: ZnCl2/HCl
30-alcohol + Lucas reagent ( immediate turbidity
20-alcohol + Lucas reagent ( turbidity after sometime
10-alcohol + Lucas reagent ( no turbidity
SAMPLE QUESTION PAPERS WITH MARKING SCHEME AND BLUE PRINT
SAMPLE PAPER –I (PREPARED BY GROUP –Platinum)
BLUE PRINT
|S.NO. |NAME OF UNIT |VSA |SA(I) |SA(II) |LONG |TOTAL |
|1 |SOLID STATE | |2X2 | | |4 |
|2 |SOLUTION | |2 |3 | |5 |
|3 |ELECTROCHEMISTRY | |2 |3 | |5 |
|4 |CHEMICAL KINETICS | | | |5 |5 |
|5 |SURFACE CHEMISTRY |1 | |3 | |4 |
|6 |GENERAL PRINCIPLE OF EXTRACTION | | |3 | |3 |
|7 |P BLOCK | | |3 |5 |8 |
|8 |THE d-& f-BLOCK ELEMENTS | |2 |3 | |5 |
|9 |CO-ORDINATION COMPOUNDS |1 |2 | | |3 |
|10 |HALOALKANES& HALO ARENES | |2X2 | | |4 |
|11 |ALCOHALS, PHENOLS & ETHERS. |1 | |3 | |4 |
|12 |ALDEHYDE, KETONES & CARBOXYLIC ACIDS |1 | | |5 |6 |
|13 |AMINES |1 | |3 | |4 |
|14 |BIOMOLECULES |1 | |3 | |4 |
|15 |POLYMERS |1 |2 | | |3 |
|16 |CHEMISTRY IN EVERYDAY LIFE |1 |2 | | |3 |
| |
| |
| |Time : 3 Hours: Class-XII |Subject :Chemistry | | |Max Time: 3Hrs | |
| | | | | | | |
|Unit |Types of questions --> |VSA |SA(I) |SA(II) |LA |Total |
|no. |Name of the unit |(1mark) |(2Marks) |(3Marks) |(5Marks) | |
|1 |Solid State |1(1) | |3(1) | |4(2) |
|2 |Solutions | | | |5(1) |5(1) |
|3 |Electrochemistry | |2(1) |3(1) | |5(2) |
|4 |Chemical Kinetics | |2(1) |3(1) | |5(2) |
|5 |Surface Chemistry |1(1) | |3(1) | |4(2) |
|6 |General Principles and Processes of Isolation of Elements | | |3(1) | |3(1) |
|7 |p-Block Elements |1(1) |2(1) | |5(1) |8(3) |
|8 |d and f - Block Elements | |2(1) |3(1) | |5(2) |
|9 |Co-ordination Compounds |1(1) |2(1) | | |3(2) |
|10 |Haloalkanes and haloarenes | |4(2) | | |4(2) |
|11 |Alcohols, Penols and ethers | |4(2) | | |4(2) |
|12 |Aldehydes, Ketones and Carboxylic acid |1(1) | | |5(1) |6(2) |
|13 |Organic compds containing nitrogen |1(1) | |3(1) | |4(2) |
|14 |Biomolecules |1(1) | |3(1) | |4(2) |
|15 |Polymers | | |3(1) | |3(1) |
|16 |Chemistry in Everday life |1(1) |2(1) | | |3(2) |
| |Total |8(8) |20(10) |27(9) |15(3) |70(30) |
SAMPLE QUESTION PAPER-II
Class-XII
Max Marks:70 Subject- Chemistry Max. Time: 3 hrs
Total no. of questions: 30 Total no. of printed pages:03
General Instructions
1. All questions are compulsory.
2. Question nos. 1 to 8 are very short answer questions and carry 1 mark each.
3. Question nos. 9 to 18 are short answer questions and carry 2 marks each.
4. Question nos. 19 to 27 are also short answer questions and carry 3 marks each
5. Question nos. 28 to 30 are long answer questions and carry 5 marks each
6. Use log tables if necessary, use of calculators is not allowed.
1.Primary amines have higher boiling point than tertiary amines. Why? (1)
2.In liquid state HCl is stronger acid than HF. Why? (1)
3.What is coordination no. of ions in a rock salt type crystal structure. (1)
4.What is meant by the term broad spectrum antibiotic? (1)
5.Why are carbohydrates generally optically active? (1)
6.Write the IUPAC name of the following: (1)
CH3
CO-N
C2H5
7.Write the IUPAC name of the complex compound [Co(NH3)6][Cr(CN)6] (1)
8.How does adsorption of a gas on a solid surface vary with (1)
increase in pressure?
9.Give reasons for the following: (2)
(a)Oxygen is diatomic while sulphure is octatomic.
(b)H2S is less acidic than H2Te
10.Using valence bond approach, deduce the shape and magnetic character of [CoF6]3- ion. (2)
11.Account for the following: (2)
(a)Dry cell become dead after a long time even it has not been used.
(b)Iron does not rust even if zinc coating is scratched in galvanized iron.
12.Discuss the two ways in which drugs prevent attachment of natural substrate active site of an enzyme. (2)
Or
Explain the following terms with suitable examples:
(i) Cationic detergents (ii) Food preservatives
13.Give reasons for the following: (2)
(i)Alcohols act as weak base.
(ii)m-aminophenol is stronger acid than o-aminophenol.
14.Describe a chemical test to distinguish between the following pairs: (2)
(i)Acetaldehyde and acetone
(ii)Benzoic acid and phenol
15.Distinguish order and molecularity of a reaction. When could order and molecularity of a reaction be the same? (2)
16.Account for the following: (2)
(i)There are irregularities in the electronic configurations of actinoids
(ii)Compounds of transition elements are often coloured.
17.State the IUPAC name of the compound (2)
[pic]
(ii)Complete the equation: CH3CH2CH=CH2 HBr/Peroxide
18.Account for the following: (2)
(i) Cl* reacts faster than Cl
(ii)The treatment of an alkyl halide with aqueous KOH leads to the formation of an alcohol whereas in the presence of alcoholic KOH, alkene is the major product.
19.The decomposition of phosphine: 4PH3(g) ( P4(g) + 6H2(g) has the rate law, Rate=k[PH3]. The rate constant is 6.0 x 10-4 S-1 at 300K and activation energy is 3.05 x 105 J/mole. Calculate the value of rate constant at 310K. (3)
20(a)What is the difference between a colloidal solution and an emulsion? Give one example of each.
(b)What are emulsifiers? (3)
21.Describe the role of following: (3)
(i)Depressant in froth floatation process.
(ii)Cryolite in metallurgy of aluminium.
(iii)Silica in the extraction of copper from copper pyrites ore.
22(a)Describe the commercial preparation of potassium permanganate from pyrolusite ore.
(b)Write ionic equation to represent the reaction of acidified KMnO4 solution with oxalic acid.
23(a)Distinguish between homo polymers and copolymers. Give one example of each. (3)
(b)Is –(-CH2-CH(C6H5)-)-n a homo polymer or a copolymer? Why?
24.What do you understand from: (3)
(a)Denaturation of protein (b)Primary structure of protein
(c) Replication
25.Illustrate the following reaction with suitable example (3)
(i)Coupling reaction
(ii)Hell Volhard Zeilnsky reaction
26.Calculate the standard cell potential of a galvanic cell in which the following reaction takes place: (3)
2 Cr(s) + 3 Cd2+(aq) ( 2 Cr3+(aq) + 3 Cd(s)
Calculate ∆G0 and equilibrium constant, K of the above reaction at 250C.
Given that E0 Cr3+/Cr = - 0.74V; E0 Cd2+/Cd = - 0.40V
27.Explain the following terms with examples: (3)
(i)Schottky defect (ii)Ferromagnetism
Or
(a)What is the coordination number of an octahedral void?
(b)Name one defect which causes colour in ionic solids. Describe that defect.
28.(a)Arrange HClO3, HClO2, HOCl and HClO4 in order of increasing acid strength. Give reasons for your answer.
(b)Write the balanced chemical equation for the reaction of Cl2 with hot and conc NaOH solution. Justify that this reaction is a disproportionation reaction.
(c)Give one use of SF6. (5)
Or
(a)Why do some noble gases form compounds with fluorine and oxygen only?
(b)Draw the structure of IF7
(c)How are the following compounds prepared from XeOF6?
(i)XeOF4 (ii)XeO3
29(a)An organic compound A, molecular formula C8H16O2 was hydrolysed with dilute sulphuric acid to give a carboxylic acid B and an alcohol C. Oxidation of C with chromic acid produced B. C on dehydration gives but-1-ene. Write chemical equations for the reactions involved.
(b)How will you carryout following conversion
(a) Propanone to Propene (b)Methane to ethyl amine
Or
An organic compound A(C7H6Cl2) on treatment with NaOH solution gives another compound B(C7H6O). B on oxidation gives an acid C(C7H6O2) which on treatment with a mixture of conc. HNO3 and H2SO4 gives a compound D(C7H5NO4). B on treatment with conc. NaOH gives a compound E(C7H8O) and C6H5COONa. Deduce the structures of A, B, C, D and E. (5)
30(a)State Henry Law and mention its two applications (5)
(b)Henry law constant for CO2 dissolving in water is 1.6 x 108 Pa at 298K. Calculate the quantity of CO2 in 1L of soda water when packed under 2.5atm. CO2 pressure at 298K
Or
(a)The depression in freezing point of water observed for the same molar concentrations of acetic acid, trichloroacetic acid and trifluoroacetic acid increases in the order as stated above. Explain.
(b)Calculate the temperature at which a solution containing 54g glucose in 250g water will freeze.(Kf for water = 1.86 K kg mole-1)
SAMPLE PAPER –III (Prepared by Gr-Copper)
BLUE PRINT
|S. No. |Unit |VSA |SA I |SA II |LA |Total |
| | |(1 Mark) |(2 Marks) |(3.Marks) |(5 Marks) | |
|01 |Solid State | |4(2) | | |4(2) |
|02 |Solution | |2(1) |3(1) | |5(2) |
|03 |Electrochemistry | |2(1) |3(1) | |5(2) |
|04 |Chemical Kinetics | | | |5(1) |5(1) |
|05 |Surface Chemistry |1(1) | |3(1) | |4(2) |
|06 |General Principles & Processes of | | |3(1) | |3(1) |
| |isolation of elements | | | | | |
|07 |P block elements | | |3(1) |5(1) |8(2) |
|08 |d- & f- block elements | |2(1) |3(1) | |5(2) |
|09 |Coordination Compounds |1(1) |2(1) | | |3(2) |
|10 |Haloalkanes & Haloarenes | |4(2) | | |4(2) |
|11 |Alcohols, phenol & ethers |1(1) | |3(1) | |4(2) |
|12 |Aldehyde, ketones & carboxylic acid |1(1) | | |5(1) |6(2) |
|13 |Organic compounds containing Nitrogen. |1(1) | |3(1) | |4(2) |
|14 |Biomolecules |1(1) | |3(1) | |4(2) |
|15 |Polymers |1(1) |2(1) | | |3(2) |
|16 |Chemistry in everyday life |1(1) |2(1) | | |3(2) |
|Total |8(8) |20(10) |27(9) |15(3) |70(30) |
Model Question Set for class XII
Time allowed: 3 Hours Maximum Marks: 70
All questions are compulsory. Question nos. 1 to 8 are very short answer questions and carry 1 mark each. Question nos 9 to 18 are short answer questions and carry 2 marks each. Question nos 19 to 27 are short answer questions and carry 3 marks each. Question nos28 to 30 are long answer questions and carry 5 marks each. Use log table if necessary .
1. Why are powdered substances more effective adsorbents than their crystalline forms? 1.
2. Write the formulas for the coordination compound Tetraamineaquachloridocobalt(III) chloride 1.
3. Give IUPAC name of the compound 1.
[pic]
4. Write the structures of products of the following reaction. 1.
[pic]
5. Arrange the following in decreasing order of their basic strength in gas phase: 1.
[pic]
6. Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six membered ring compounds) are insoluble in water. Explain. 1.
7. What is monomer of PTFE? 1.
8. With reference to which classification has the statement, “ranitidine is an antacid” been given? 1.
9. X-ray diffraction studies show that copper crystallizes in an fcc unit cell with cell edge of 3.608×10-8 cm. In a separate experiment, copper is determined to have a density of 8.92 g/cm3, calculate the atomic mass of copper. 2.
Or
Silver crystallizes in fcc lattice. If edge length of the cell is 4.07 × 10–8 cm and density is 10.5 g cm–3, calculate the atomic mass of silver. 2.
10. In terms of band theory, what is the difference (i) between a conductor and an insulator (ii) between a conductor and a semiconductor? 1+1=2
11. State Henry’s law and mention some important applications? 1+1=2
12. Explain how rusting of iron is envisaged as setting up of an electrochemical cell. 2
13. What is meant by ‘disproportionation’ of an oxidation state? Give an example. 2
14. Write the IUPAC names of the following coordination compounds:
(i) [Pt(NH3)2 Cl(NO2 )] (ii) K3 [Cr(C2 O4 )3 ] 2
15. Which alkyl halide from the following pairs would you expect to react more rapidly by an SN2 mechanism? Explain your answer.
(i)CH3CH2CH2CH2Br & CH3CH2CH(Br)CH3 2.
(ii) [pic]
16. Draw the structures of major monohalo products in each of the following reactions: 1/2x4=2
[pic]
17. Write the names of monomers of the following polymers: 1+1=2 [pic]
18. Sleeping pills are recommended by doctors to the patients suffering from sleeplessness but it is not advisable to take its doses without consultation with the doctor. Why ?
19. Vapour pressure of chloroform (CHCl3) and dichloromethane (CH2Cl2)at 298 K are 200 mm Hg and 415 mm Hg respectively. (i) Calculate the vapour pressure of the solution prepared by mixing 25.5 g ofCHCl3 and 40 g of CH2Cl2 at 298 K and, (ii) mole fractions of each component in vapour phase.
Or
Two elements A and B form compounds having formula AB2 and AB4. When dissolved in 20 g of benzene (C6H6), 1 g of AB2 lowers the freezing point by 2.3 K whereas 1.0 g of AB4 lowers it by 1.3 K.
The molar depression constant for benzene is 5.1 K kg mol–1 Calculate atomic masses of A and B.
20. (i)Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging.
(ii) Explain how rusting of iron is envisaged as setting up of an electrochemical cell.
21. (i)What is the difference between physisorption and chemisorption?
(ii)Give two examples of heterogeneous catalysis.
(iii)What is shape selective catalysis?
22. (i) What is the role of depressant in froth floatation process? 1
(ii) Write down the reactions taking place in different zones in the blast furnace during the extraction of iron. 2
23. Write balanced equations for the following: 1x3= 3
(i) NaCl is heated with sulphuric acid in the presence of MnO2.
(ii) Chlorine gas is passed into a solution of NaI in water.
(iii) Ammonia reacts with a solution of Cu2+?
24. Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with (i) iron (II) ions (ii) SO2? Write the ionic equations for the reactions. 1+2 = 3
25. (a) Write the equations involved in the following reactions: 2+1 =3
i) Reimer - Tiemann reaction
(ii) Kolbe’s reaction
(b)Explain why propanol has higher boiling point than that of the hydrocarbon butane?
26. How will you convert
(i)Benzene into aniline (ii) Benzene into N, N dimethylaniline
(iii) Cl–(CH2)4–Cl into hexan-1,6-diamine?
27. (i) What products would be formed when a nucleotide from DNA containing thymine is hydrolysed?
(ii)When RNA is hydrolysed, there is no relationship among the quantities of different bases obtained. What does this fact suggest about the structure of RNA?
ii) What are monosaccharides?
28. (i) Determine the order of reaction represented by following time/ concentration graph. 1+2+2=5
[pic]
Show that in a first order reaction, time required for completion of 99.9% is 10 times of half-life (t ) of the reaction.
The following results have been obtained during the kinetic studies of the reaction:
2A + B → C + D
[pic]
Determine the rate law and the rate constant for the reaction.
Or 2+2+1=5
i) The decomposition of hydrocarbon follows the equation[pic]Calculate E a.
ii) The following data were obtained during the first order thermal decomposition of SO2Cl2 at a constant volume.
[pic][pic]
Calculate the rate constant of the reaction
iii) What is the order of I st order reaction
29. Conc H2SO4 placed in the five test tubes as shown below [pic]
With the help of chemical equation explain in which test tube
i) The Black residue formed
ii) A pungent smelling gas produced which change the acidified potassium dichromate solution green.
iii) Yellow powder disappears to produce pungent smelling gas which change the acidified potassium dichromate solution green.
iv) Orange red gas produced.
v) Black powder disappears.
OR
Give reason for the following :-
i) Bond angle in PH4+ is higher than that in PH3.
ii) PCl3 fume in moisture.
iii) O3 act as a powerful oxidising agent.
iv) In vapour state sulphur shows paramagnetic behavior.
v) Halogens have maximum negative electron gain enthalpy in the respective periods of the periodic table.
30. (a) An organic compound with the molecular formula C9H10O forms 2,4-DNP derivative, reduces Tollens’ reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1,2-benzenedicarboxylic acid. Identify the compound.
(b) How will you bring about the following conversions in not more than two steps?
(i) Propanone to Propene (ii) Benzoic acid to Benzaldehyde
Or
a) An organic compound (A) (molecular formula C8H16O2) was hydrolysed with dilute sulphuric acid to give a carboxylic acid (B) and an alcohol (C). Oxidation of (C) with chromic acid produced (B). (C) on dehydration gives but-1-ene.
Write equations for the reactions involved.
b) Arrange the following compounds in increasing order of their property as indicated: (i) Acetaldehyde, Acetone, Di-tert-butyl ketone, Methyl tert-butyl ketone (reactivity towards HCN)
(ii) CH3CH2CH(Br)COOH, CH3CH(Br)CH2COOH, (CH3)2CHCOOH, CH3CH2CH2COOH (acid strength)
ANSWER KEY
1. Due to large surface area of powdered solid. 1 mark
2. [Co(NH3)4 H2O Cl]Cl2 1 mark
3. 2,6-Dimethyl phenol. 1 mark
4. C6H5COC2H5 1 mark
5. Aniline < Ammonia < Ethanamine < Di ethyl amine. 1 mark
6. Sucrose or Glucose contain many polar O-H groups hence these are soluble in water. 1 mark
7. Tetra floro ethane 1 mark
8. On the basis of target molecule. 1 mark
9. Edge length =3.608×10-8 cm, density = 8.92 g/cm3, Z= 4 (FCC) Mol. Mass =? d = Z M/ a3NA 2 mark
M= d a3 NA/ Z = 8.92 g/cm3 x (3.608x10-8 cm)3 x 6.02x1023mol-1
4
= 62.9 gmol-1
Or 2mark
Edge length = 4.07 × 10–8 cm density = 10.5 g cm–3 Z=4
Mol. Mass =? d = Z M/ a3NA
M= d a3 NA/ Z =[10.5 g cm–3 x (4.07 × 10–8 cm)3 x 6.02x1023mol-1]/4
= 106.98 g mol-1
10. (i) In Conductor no energy gap present whereas in insulator a large energy gap present between valance band and conduction band 1mark
(ii) In Conductor no energy gap present whereas in semiconductor a small energy gap present between valance band and conduction band. 1 mark
11. Henry’s law:- Solubility (mole fraction) of a gas in a liquid is directly proportional to its (gas) partial pressure. 1 mark
P = KH χ
Applications of Henry’s law:- (a) To determine solubility of a gas (b) In cold drinks industry 1 mark
12. rusting of iron :- 1 mark
Fe -( Fe 2+ + 2e- , (Anode reaction)
4H+ + O2 + 4e- ( 2 H2O (Cathode reaction) 1 mark
Fe 2+ + H2O + O2 ( Fe2O3 . x H2O
13. Disproportionation’ of an oxidation state:- If oxidation state of an element in a compound disproportionate ( increase and decrease) In the reaction to form two different products then it is called Disproportionation’ of an oxidation state. 1 mark
Cl2 + OH- (Dil & Cold) ( Cl- + ClO- + H2O 1 mark
14. (i) [Pt(NH3)2 Cl(NO2 )] Diaminechloridonitro(o)platinum(II) 1 mark
(ii) K3 [Cr(C2 O4 )3 ] Potassium trioxalatochromate(III) 1 mark
15. i) Out of CH3CH2CH2CH2Br & CH3CH2CH(Br)CH3 , CH3CH2CH2CH2Br is more reactive since it is primary halide. 1 mark
(ii) Out of [pic] Cyclohexile methyl chloride is more reactive since it is primary halide 1 mark
17 Each reaction ½ mark
18. (I) Hexamethylene di amine and adipic acid (ii) Caprolactum. 1+1=2marks
over dose of sleeping piles may harm the patient so it must be taken under proper guidance of a doctor. 1 mark
19. P0 (CHCl3) = 200 mm Hg P0 (CH2Cl2) = 415 mm Hg 1 mark
Mass of(CHCl3) = 25.5g Mass of(CH2Cl2) = 40 g
n(CHCl3) = 25.5/119.5 = 0.213mole n(CH2Cl2) =40/85 =0.47mole
X(CHCl3) = n(CHCl3) / n(CHCl3) + n(CH2Cl2) =0.313
X(CH2Cl2) =0.687.
P = P0 (CHCl3) X(CHCl3) + P0 (CH2Cl2) X(CH2Cl2) = 347.9 1 mark
p = 0.688 × 415 mm Hg = 285.5 mm Hg
(CHCl3)p = 0.312 × 200 mm Hg = 62.4 mm Hg
(CH2Cl2) y = 285.5 mm Hg/347.9 mm Hg = 0.82
(CHCl3) y = 62.4 mm Hg/347.9 mm Hg = 0.18. 1 mark
Or
Ans – A =25.58u B= 42.64u 3 mark
20. (i) 1.5 mark [pic]
1.5 mark
(ii) [pic]
21. (i) Wrtite difference mark 1
(ii) Four equations mark 1
(iii) Write definition mark 1
22 (i) Role of depressant 1 mark
(ii) Reactions in blast furnace 2 marks
23. Each reactions 1 mark.
24. Preparation 1 mark, reactions 2 marks.
25. Reaction 2marks , reasoning 1 mark
26. Three conversions 1 mark each.
27. Hydrolysis product 1 mark, each Definitions 1 mark
28. Zero order reaction 1 mark,
Solution of numerical 2 marks each.
or
i) Numerical – Formula writing ½ mark, comparison 1/2 mark, Calculation 1mark.
ii) Numerical – Formula writing ½ mark, comparison 1/2 mark, Calculation 1mark.
iii) Definition 1mark
29. Five reactions ofone mark each,
or
Reasoning questions 1 mark each
30. (a) Identification of compounds 1 mark , Reaction 2 marks
(b) Each conversion 1
Or
a) Identification of compound 2 marks, Reactions involved 2 marks.
b) Arrangement of compound 1 mark
SAMPLE PAPER – IV (Prepared By Group-Silver)
|BLUE PRINT |
|CLASS XII SUBJECT: CHEMISTRY MAX. MARKS : 70 |
|TIME : 3 HOURS |
|UNIT |NAME OF THE UNIT |KNOWLEDGE |UNDERSTANDING |APPLICATION AND SKIL |TOTAL |
|NO. | | | | | |
| | |VSA |SA |SA |LA |
| | |1 |2 |3 |5 |
| |
|NOTE : - 1. Number of questions are written within the bracket and their marks out side the bracket. |
|2. Internal choice maybe given for all LA (5 marks) , one SA (3 marks) and one SA (2 marks). |
|3. Numercial problems may be given for 8 to 10 marks. |
| WEIGHTAGE TO TYPE OF QUESTIONS | WEIGHTAGE TO LEARNING OUTCOMES | WEIGHTAGE TO |
| | |DIFFICULTY LEVEL |
|VSA TYPE QUESTIONS OF IMARK :08 |KNOWLEDGE : 21 MARKS (30 %) | |
|SA TYPE QUESTIONS OF 2 MARKS : 10 |UNDERSTANDING : 35 MARKS (50 %) |EASY : 15 %|
|SA TYPE QUESTIONS OF 3 MARKS : 09 |APPLICATION : 10 MARKS (14 %) |AVERAGE : 70 % |
|LA TYPE QUESTIONS OF 5 MARKS : 03 |SKILL : 04 MARKS (06 %) |DIFFICULT : 15 % |
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SAMPLE PAPER-IV
CLASS : XII SUB: CHEMISTRY
TIME: 3 HOURS MAX. MARKS: 70
General Instructions:
1. All questions are compulsory.
2. Question numbers 1 to 8 are very short answer questions of one mark each. Answer these in one word or about one sentence each.
3. Question numbers 9 to 18 are short answer question of two marks each. Answer these in about 30 words each.
4. Question numbers 19 to 27 are short answer question of three marks each. Answer these in about 40 words each.
5. Question numbers 28 to 30 are long answer question of five marks each. Answer these in about 70 words each.
6. Use log tables, if necessary.
1. Name the catalyst and the promoter used in Haber’s process for manufacture of ammonia. 1
2. Give the IUPAC name of : [Co(NH3)Cl(en)2] Cl2 1
3. Write the structure of : [pic] 1
4. Give the IUPAC name of the organic compound 1
(CH3)2 C═ CH C CH3
│
OH
5. Name the type of bonding which stabilizes (-helix structure in proteins. 1
6. What do you mean by homopolymers? 1
7. How will you distinguish between primary aliphatic amine and secondary aliphatic amine? 1
8. Give one example of an artificial sweetener used by the diabetic patients. 1
9. (a)Name the type of point defect that occurs in a crystal of zinc sulphide. 1x2=2
(b)How many octahedral voids are there in l mole of a compound having cubic close packed structure?
10. An element X with an atomic mass of 60g/mol has density of 6.23g cm-3. If the edge length of its cubic unit cell is 400 pm, identify the type of cubic unit cell. 2
11. Give reasons for the following:
(i)At higher altitudes, people suffer from a disease called anoxia. In this disease, they become weak and
cannot think clearly.
(ii) Write the unit of molal elevation constant 2x1=2
12. Write the chemical equations for all the steps involved in the electrochemical theory of rusting of iron. Give any one method to prevent rusting. 2
13. Explain the following facts
(a) Chromium group elements have the highest melting points in their respective series.
(b) Transition metals form coloured complexes. 2x1=2
14. (a)Give the electronic configuration of the d- orbitals of Ti in [Ti (H2O)6] 3+ ion in an octahedral crystal
field.
(b)Why is this complex coloured? Explain on the basis of distribution of electrons in the d- orbitals.
2x1=2
OR
b) Name the isomerism exhibited by the following pair of coordination compounds:
[Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br
c) Give one chemical test to distinguish between these two compounds. 2x1=2
15. (a)Vinyl chloride is less reactive than ethyl chloride towards nucleophilic substitution reaction.
Explain why?
(b)Haloalkanes react with KCN to give alkyl cyanide as main product while with AgCN they form
isocyanides as main product. Give reason. 2x1=2
16. Write the formula of main product formed in the following chemical reactions. 4x ½=2
Na
i) (CH3)2 CH-C1 ──────→
Dry ether
∆
ii) CH3Br + AgF──────→
Dry acetone
iii) CH3CH2Br + Nal ───────→
Cu /HCl
iv) C6H5N2Cl ───────→
17. Write name of monomer of the following polymers and classify them as addition or condensation polymers.
(a) Teflon (b) Natural Rubber 2x1=2
18. Define the following :- (a) Antiseptic (b) Disinfectant with one example of each. 2x1=2
19. Ethylene glycol (molar mass = 62 g mol¯ 1) is a common automobile antifreeze. Calculate the freezing point of a solution containing 12.4g of this substance in 100 g of water. Given : Kf for water = 1.86K kg/mol. 3
20. Calculate the equilibrium constant for the reaction 3
[pic]
OR
Calculate the standard free energy change for the following reaction at 250C
[pic]
21. (a) Adsorption of a gas on the surface of solid is generally accompanied by a decrease in entropy. Still it
is a spontaneous process. Explain.
(b) How does an increase in temperature affect both physical as well as chemical adsorptions? 1+2=3
22. (a) Name the method used for refining of (i) Nickel (ii) Zirconium. 2 x ½ +2=3
(b)Write the chemical equation of the reactions involve in the extraction of Au by leaching with NaCN.
23. Account for the following: 3x1=3
(a) N2 is inert at room temperature.
(b) catenation tendency of nitrogen lesser than that of phosphorus
(c) PCl3 fume in atmosphere
24. Give reasons for the following: 3x1=3
(a) Among the lanthanoids, Ce(III) is easily oxidised to Ce(IV).
(b) Fe3+ / Fe2+ redox couple has less positive electrode potential than Mn3+ / Mn2+couple.
(c) The second and third transition series elements have almost similar atomic radii.
25.(a) Write the formation of diethyl ether from ethanol in the presence of concentrated sulphuric acid.
(b) How do you account for the miscibility of ethoxyethane with water? 2+1=3
26. (i)Complete and name the following reactions:
[pic]
(ii) How will you distinguish between: C6H5NH2 and CH3NH2 ? 2+1=3
27. (a)Draw the Haworth structure of (-D-(+)-Glucopyranose
(b) Name the two components of starch. How do they differ from each other structurally? 1+2=3
28. (i)
[pic]
Answer the following questions on the basis of the above curve for a first order reaction A → P:-
(a) What is the relation between slope of this line and rate constant? (1)
(b) Calculate the rate constant of the above reaction if the slope is 2 x 10-4 s-1
(ii)The decomposition reaction of ammonia gas on platinum surface has a rate constant k = 2.5 x 10–4
mol L–1 s–1.What is the order of the reaction?
(iii) For an elementary reaction 2A + B → 3C, the rate of appearance of C at time‘t’ is 1.3 x 10-4 mol
L-1 s-1.Calculate at this time
(a) Rate of the reaction.
(b) Rate of disappearance of A. 2x1+1+2x1=5
OR
For a certain chemical reaction A + 2B → 2C + D,the experimentally obtained information is tabulated below.
|Experiment |[A]o in mol/L |[B]o in mol/L |Initial rate of the reaction |
| | | |in moll-1s-1 |
|1 |0.30 |0.30 |0.096 |
|2 |0.60 |0.30 |0.384 |
|3 |0.30 |0.60 |0.192 |
|4 |0.60 |0.60 |0.768 |
For this reaction
(i) Derive the order of reaction w.r.t. both the reactants A and B.
(ii) Write the rate law.
(iii) Calculate the value of rate constant k
(iv) Write the expression for the rate of reaction in terms of A . 2+1+1+1=5
29. (i) Give reasons for the following
a) Fluorine exhibits only – 1 oxidation state whereas other halogens exhibit higher positive oxidation states also.
b) CN¯ ion is known but CP¯ ion is not known.
c) NO2 dimerises to form N2O4
d) ICl is more reactive than I2
(ii) Predict the shape of CIF3 on the basis of VSEPR theory. 4x1+1=5
OR
(a)What is the covalence of nitrogen in N2O5?
(b) Explain why both N and Bi do not form pentahalides while phosphorus does.
(c)Why does chlorine water lose its yellow colour on standing?
(d) What happens when Cl2 reacts with cold dilute solution of sodium hydroxide? Write equation only.
(e) Write down the equations for hydrolysis of XeF4. 5x1=5
30. (a) An organic compound ‘A’ with molecular formula C5H8O2 is reduced to n-pentane on treatment
with Zn-Hg/HCl. ‘A’ forms a dioxime with hydroxylamine and gives a positive iodoform test and
Tollen’s test. Identify the compound ‘A’ and deduce its structure.
(b) Write the chemical equations for the following conversion:
(i) Ethyl benzene to benzoic acid
(ii) Acetaldehyde to 3-hydroxy butanal
(iii) Acetone to propan-2-ol 2+3=5
OR
(a)An organic compound (A) having molecular formula C8H8O gives positive DNP and iodoform
test. It does not reduce Tollen’s or Fehling’s reagent and does not decolorize bromine water also. On
oxidation with chromic acid, it gives a carboxylic acid (B) with molecular formula C7H6O2. Deduce
the structures of ‘A’ and ‘B’.
b) Complete the following reactions by identifying A, B and C.
Pd/BaSO4
ii) A + H2(g) ────────→ (CH3)2CH-CHO
i) 2HCHO + conc. NaOH ────────→ B + C 3+2=5
************************************************************************************
Marking Scheme
1. Promotor-Mo/Al2O3, Catalyst-Fe ½+ ½ = 1
2. amminechloridobis-(ethane-1,2-diamine)cobalt(III) chloride 1
3. [pic] 1
4. 4-methylpent-3-en-2-ol 1
5. intra molecular hydrogen bonding 1
6. polymers made up of only one kind of monomers 1
7. isocyanide test (carbyl amine reaction) or Hinsberg’s test 1
8. Sucrolose 1
9. (a) Frenkel defect………….1
(b) 1 mole voids …………...1
10. Given ; d= 6.23g cm-3
M=60g/mol
a = 400 pm = 4 x 10-8 cm
z = ?.................................................................................1/2
we know that d= Mz/a3 NA
z= d. a3. NA/M…………………………………1/2
= 6.23 x 64 x 10-24 x 6.023 x 1023/ 60
= 4.0018…………………………………….1/2
Z = 4 ( fcc structure)…………………….1/2
11. (a) decrease in partial pressure of dioxygen………………………………………………..1
(b) K Kg mol-1 1
12. Anode : 2Fe→ 2Fe2+ + 4 e- 1/2
Cathode O2 + 4 H+ + 4e- → 2H2O 1/2
The overall reaction is
2Fe + O2 + 4H+ → 2Fe2+ + 2H2O
2Fe2+(aq.) + H2O (l) + ½ O2 → Fe2O3 + 4H+ 1/2
Fe2O3 then combine with requisite amount of water to form Fe2O3.xH2O that is rust. Method of electroplating may be used to prevent rusting. 1/2
13. (a) presence of half filled (n-1)d subshell 1
(b) d-d transition of (n-1)d electrons 1
14. (a)[Ar]183d1 1
(b)due to d-d (draw splitting of d orbitals) 1
OR
(a) ionisatios isomerism 1
(b) BaCl2 test and AgNO3 test 1
15. (a) resonance stabilization of vinyl chloride makes it less reactive than ethyl chloride towards nucleophilic substitution reaction. 1
(b)because ionic bond is present in KCN whereas the bonding in AgCN is covalent. 1
16. Write the formula of main product formed in the following chemical reactions.
Na
a) (CH3)2 CH-C1 ──────→ (CH3)2 CH-CH(CH3)2 1/2
Dry ether
∆
b) CH3Br + AgF──────→CH3F 1/2
Dry acetone
c) CH3CH2Br + Nal ───────→ CH3CH2I 1/2
Cu /HCl
d) C6H5N2Cl ───────→C6H5Cl ½
17. (a) Teflon- tetra fluoro ethane (addition polymer) ½ + ½ =1
(b) Natural Rubber – isoprene (add. Polymer) ½ + ½ =1
18. (a) Antiseptic – chemical compound which are used to prevent or kill the harmful micro organisms and
are safe to apply on living tissue
example dettol ½ + ½ =1
(b) Disinfectant- chemical compound which are used to prevent or kill the harmful micro organisms but
are not safe to apply on living tissue. They are used in drains, toilets, wash basins etc.
example-phenol 2 % solution ½ + ½ =1
19. Given;
M2= 62 g mol-1 W2=12.4g W1= 100 g Kf for water = 1.86K Kg/mol. 1
We know that ∆Tf= Kf.W2.1000/M2.W1 1
= 1.86K Kg/mol x 12.4g x 1000/62 g mol-1 x 100g 1/2
= 3.72 K 1/2
20. equilibrium constant for the reaction is
E0 cell = E0 r – E0 l 1/2
= -0.403-(-0.763) V
= 0.36 V 1
E0 cell = (0.0591/n) log Kc 1/2
log Kc = 0.36 V x 2 / 0.0591 1/2
=12.18
Kc = antilog of 12.18 1/2
OR
Calculate the standard free energy change for the following reaction at 250C
E0 cell = E0 r – E0 l 1/2
= - 2.87 – 1.5
= - 4.37 V 1/2
We know that
∆G0 = - nF E0 cell 1
= -2 x 96500 C x (-4.37V) 1/2
=8.43 x 105 J 1/2
21. (a) Adsorption of a gas on the surface of solid is a exothermic process 1
(b) Physical adsorption decreases with rise in temperature whereas chemisorption initially increases and then decreases with rise in temperature 1 + 1
OR
(a) (i) Nickel- Mond’s process (ii) Zirconium- Van – Arkel method ½ + ½ =1
(b) (i) 4Au(s) + 8CN–(aq)+ 2H2O(aq) + O2(g) → 4[Au(CN)2]– (aq) +4OH–(aq) 1
(ii) 2[Au(CN)2]– (aq) + Zn → [Zn(CN)4]2- + 2Au 1
(a) because of high bond enthalpy due tothe presence of triple bond in N2. 1
(b) because of weaker N-N bonds whereas P-P bonds are much stronger with higher bond energy. 1
(c) PCl5 [pic] PCl3 + Cl2 1
(a) vacant (n-2) f subshell in Ce(IV). 1
(b) extra stability of Fe3+ than Mn3+ ion 1
(c) Due to lanthanoid contraction 1
(a) C2H5OH -------------→ C2H5OC2H5 2
(b) intermolecular hydrogen bonding makes ethoxyethane miscible with water 1
(i) Carbyl ammine reaction
RNH2 + CHCl3 + 3 KOH → RNC + 3KCl + 3H2O ½ + ½ =1
(ii) Hoffman bromamide reaction
RCONH2 + Br2 + 4NaOH → RNH2 + 2NaBr + Na2CO3 + 2H2O ½ + ½ =1
(iii) Azodye test 1
(a) Haworth structure of (-D-(+)-Glucopyranose 1
[pic]
b) amylase and amylopectine.
c) Amylase is a linear polymer whereas amylopectine is a branched polymer 1+1
(i) (a) slope = k/2.303 1
(b) k = slope x 2.303
= 2 x 10-4 s-1 x 2.303
= 4.6 x 10-4 s-1 1
(ii) zero order reaction 1
(iii) (a) rate of reaction = 3 x is 1.3 x 10-4 mol L-1 s-1
= 3.9 x 10-4 mol L-1 s-1 1
(b) Rate of disappearance of A = 3/2 x 1.3 x 10-4 mol L-1 s-1
= 1.95 x 10-4 mol L-1 s-1 1
(i) order of reaction w.r.t. A=2 and B = 1 1+1
(ii) rate = k [A]2[B] 1.
(iii) rate constant k = rate/[A]2[B] 1
(iv) rate of disappearance of A = -∆[A]/ ∆t 1
(i) a. Fluorine is the most electronegative element 1
b. Due to the large size of P atom it can not form multiple bond with carbon. 1
c. NO2 contains odd number of valence electrons. It behaves as a typical odd molecule. On dimerisation, it is converted
to stable N2O4 molecule 1
d. I-Cl bond is weaker than I-I bond 1
(ii) bent ‘T’ shape 1
OR
(a) covalence is 5 1
(b) N can not expand its covalence to five due to absence of d-subshell whereas Bi do not form pentahalides due to inert pair effect. 1
(c) Chlorine water on standing loses its yellow colour due to the formation of HCl and HOCl. 1
(d) 2NaOH + Cl2 −−−−−( NaCl + NaOCl + H2O 1
(e) 6XeF4 + 12 H2O −−−−−( 4Xe + 2Xe03 + 24 HF + 3 O2 1
30. (a) A is a straight chain organic compound with carbonyl functional group.
Formation of dioxime suggests the presence of two carbonyl groups. ½ It is positive towards iodoform test which indicates presence of CH3CO- group 1/2.
Positive tollens reagent test indicates the presence of –CHO group. 1/2
Therefore the organic compound is 4-oxo pentanal 1/2
(b)
(i) n-propyl benzene to benzoic acid 1
[pic]
(ii) Acetaldehyde to 3-hydroxy butanal 1
[pic]
ii) Acetone to propan-2-ol 1
CH3COCH3 + H2 ────────→ CH3CH(OH)CH3
OR
(a)Compound C8H8O gives positive DNP and iodoform test indicates the presence of CH3CO- group. 1
It does not reduce Tollen’s or Fehling’s reagent which indicates the presence of ketonic functional group. 1
On oxidation with chromic acid, it gives a carboxylic acid (B) with molecular formula C7H6O2. Therefore compound A is C6H5COCH3 and compound B is C6H5 COOH. 1
c) Complete the following reactions by identifying A, B and C.
Pd/BaSO4
iii) (CH3)2CH-COCl + H2(g) ────────→ (CH3)2CH-CHO 1
iv) 2HCHO + conc. NaOH ────────→ HCOONa + CH3OH ½ + ½
************************************************************************************
-----------------------
Example : See no 7 in the table
413 K/ conc. H2SO4
Ni/Pt
[pic]
[pic]
[pic]
[pic]
[pic]
[pic]
No. of Octahedral voids (N) = ccp arrangement of the sphere(N)=2*No. of tetrahedral voids(N)
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