Tutorial 1 - Yola



TUTORIAL : MATTER

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1 (a) An atom X is twice as heavy as one carbon –12 atom. Calculate the relative atomic mass of element X.

(b) The relative atomic mass of element Y is 32. Calculate the mass of one atom of Y in gram.

2 (a) Chlorine isotopes occur naturally as 35Cl and 37Cl. The ratio of the relative abundance of these two isotopes is : 35Cl = 3.127

37Cl

Based on the scale of 12C = 12.00, the relative mass of 35Cl and 37Cl are 34.9689 a.m.u. and 36.9659 a.m.u. respectively. Calculate the relative atomic mass of chlorine.

(b) The following is the mass spectrum of zirconium. Calculate the relative atomic mass of zirconium.

52

%

intensity 14 13

12

9

90 91 92 93 94 mass (a.m.u)

3 (a) Define :

i. Isotope

ii. Proton number

iii. Nucleon number

(b) The element of iron consists of 5.82% 54Fe, 91.66% 56Fe, 2.19% 57Fe and 0.33% 58Fe.The isotopic mass of these four isotopes are 53.9396, 55.9394, 56.9354 and 57.9333 respectively. Calculate the relative atomic mass of iron.

4 (a) Explain the process of determining atomic mass using the mass spectrometer.

b) The isotopes of Ag occur naturally as 107Ag and 109Ag with their atomic mass of 106.906 a.m.u and 108.868 a.m.u respectively. If the relative atomic mass of Ag is 107.868, what would be the percentage relative abundance of these two isotopes?

5 (a) Referring to the periodic table;

i. what are the sub atomic particles that make up the following elements: silicon-28, chlorine-37 and bromine-79.

ii. identify the species A, B, C and D.

|Species |Number of |

| |protons |neutrons |electrons |

|A |1 |0 |2 |

|B |1 |1 |0 |

|C |9 |10 |10 |

|D |2 |2 |2 |

b) The element Mg consists of three isotopes which are 24Mg, 25Mg and 26Mg.

The relative atomic mass of Mg is 24.3.

i. Which is the most abundant isotopes of Mg?

ii. State the number of protons and the number of neutrons of this isotope.

6 (a) A sample of oxygen which contains 2 isotopes with nucleon number 16 and 18, is analyzed in a mass spectrometer. How many peaks would be expected in the mass spectrum of oxygen? Explain your answer.

(b) Determine the molecular formula of compound A, which has an empirical formula CH2O and its relative molecular mass is 90 g mol-1.

7 Calculate the relative molecular mass of each of the following compounds

i. glucose, C6H2O6

ii. copper (II) sulphate, CuSO4

iii. magnesium oxide, MgO

8 Calculate :

i. the number of atoms in 5 g of Ag

ii. the number of molecules in 25 g of methane, CH4

iii. the number of carbon atoms in 0.5 mol of ethane, C2H4.

9 Quinine C20H24N2O2, is a compound extracted from cinchona tree which is traditionally used to treat malaria. If given 1.08 g of quinine sample, calculate:

i. molecular weight of quinine,

ii. the number of moles of quinine,

iii. the number of molecules of quinine,

iv. the number of hydrogen atoms,

v. the mass of carbon atoms in grams.

10 72 cm3 sample of NH3 gas is allowed to react with oxygen at room temperature and 1 atm according to the equation:

4NH3 (g) + 5O2 (g) 4NO(g) + 6H2O (l)

Calculate the number of molecules of water produced.

11 Determine the oxidation number of the underlined elements in the following compounds

i. NO2 iv. H2SO4

ii. KMnO4 v. Cr2O72-

iii. HClO3 vi. I O3-

12 Balance each of the following equation

i. NaOH (aq) + FeCl3 (s) Fe(OH)3 (s) + NaCl (aq)

ii. C4H10 (g) + O2 (g) CO2 (g) + H2O (l)

iii. Fe (s) +H2O (l) Fe3O4 (s) + H2 (g)

iv. Fe2O3 (s) +HCl (aq) FeCl3 (aq) +H2O (l)

v. Cr(OH)3 (aq) + IO 3 - (aq) CrO 3 2 - (aq) + I- (aq) (acidic)

vi. Cl2 (aq) ClO4- (aq) + Cl- (aq) (basic)

TUTORIAL 2 : ATOMIC STRUCTURE

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1 (a) What is the difference between continuous spectrum and line spectrum?

(b) Explain the difference between ground state and excited state.

(c) Briefly describe Bohr’s theory of the hydrogen atom.

2 (a) Explain why the emission spectrum of hydrogen atom is a line spectrum?

(b) How is the second line of Brackett series produced?

3 The first line of Balmer series has a wavelength of 656.3 nm. Calculate the energy difference between the two energy levels that produced this line?

4 When an electron makes a transition from higher energy level to lower energy level, a photon with the frequency of 6.6 x 1015 Hz Is emitted. Calculate:

a) the wavelength of the photon.

b) energy for 1 mole of electron for the above transitions.

(c) What is the energy and wavelength of a photon emitted during a transition from

the fifth energy level to the second energy level?

(d) Describe de Broglie’s postulates and Heisenberg’s uncertainty principle.

5 State the maximum electrons that can be occupy an orbital with the following quantum

numbers:

(a) n=2, l =0, s =-1/2 (b) n=3, l=2 (c) n=5, l=1

6 Which of the following quantum numbers are allowed? Explain your answer.

(a) (1, 1, 0, +1/2) (b) (3, 1, -2, +1/2)

(c) (2, 1, 0, +1/2) (d) (2, 0, 0, +1)

7 (a) State Aufbau’s principle.

(b) Arrange the following orbitals according to increasing energy level.

4dxy, 3dxy, 3dyz, 4pz, 3pz, 3py, 2py, 3s, 2s, 1s

8 Give one set of possible quantum number for one electron in the following orbital.

(a) 1s (b) 2s (c) 3p (d) 3d

9 Give the expected ground state electron configuration for atoms with the

following atomic numbers:

(a) Z=55 (b) Z=40 (c) Z=62

10 (a) State Hund’s rule and Pauli’s exclusion principle.

(b) Write the electronic configurations for Al, K, Cr and Cu. Explain the anomalous electron configuration in chromium and copper.

(c) Atom X has 5 electrons.

i. Write the electronic configuration for X.

ii. Give a set of quantum numbers for each of valence electrons.

TUTORIAL 3: PERIODIC TABLE

1 The table below shows the group and period of the elements P, Q, R, S and T.

|Element |Period |Group |

|P |2 |15 |

|Q |2 |18 |

|R |3 |1 |

|S |4 |17 |

|T |4 |16 |

(a) Write the electronic configuration for each of the element

(b) Write the electronic configuration for P 3- , R + and S - .

(c) State the block (s, p or d) for each element

2 State the period, group and block for each element below

A : 1s2 2s2 2p6 3s2 3p6

B : 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5

C : 1s2 2s2 2p6 3s2 3p6 4s2

3 Element Y has electronic configuration of 1s2 2s2 2p6 3s2 3p5.

(a) State the number of valence electron.

(b) Determine the main oxidation number.

(c) Identify element Y.

4 The first six ionization energies of element X are shown below:

|Ionization |IE1 |

|Energy (kJ / mol) | |

|W |[Ne]3s1 |

|X |[Ne] 3s23p4 |

|Y |[Ar]4s2 |

|Z |[Ar]3d104s24p4 |

(a) Explain

i. the difference in the first ionization energy between element W and X

ii. the difference in ionic radius between X 2- and Y 2+

(b) Among elements X, Y and Z, which has

i. the lowest electron affinity?

ii. the highest oxidizing ability?

(c) Write the molecular formula of the substance formed when Y reacts with oxygen. How does the substance behave in aqueous solution?

6 The graph below shows the variation of ionization energies for element Z.

log ionization energy

[pic]

number of electrons removed

6 (a) State the group and period for element Z.

(b) Name element Z.

(c) Why does it need a higher energy to remove the fourth electron?

(d) Explain how does the atomic radius of Z change when an electron is removed.

(e) State the change of atomic radius of Z when an electron is added.

(f) State the oxidation number of element Z.

TUTORIAL 4: CHEMICAL BONDING

1. Complete the table below :

| Group |1 |2 |

|mixture of O2, N2 and CO2 gases | | |

|mixture of ethanol and water | | |

|immiscible solution of benzene and water | | |

|HNO3(aq) which is in an equilibrium with its | | |

|vapour | | |

3 Substance X has its triple point at 18 ○C and 0.5 atm. The melting point and boiling point are 20 ○C and 300 ○C respectively. Sketch the phase diagram for X.

4 Xenon is a noble gas. The melting point and boiling point for xenon are -112 ○C and -107 ○C respectively. The triple point of xenon is at -121 ○C and 282 torr whereas the critical point is at 16.6 ○C with a pressure of 57.6 atm.

(a) Sketch and label a phase diagram for xenon.

(b) Compare the density of xenon in liquid and solid phases.

5 Figure below shows the phase diagram for water.

P

T

Fig. 7.1

(a) Which curve represent the equilibrium of ice and water vapour?

(b) State the phase changes when a sample at point E is heated at constant pressure until point F is reached.

(c) Name the point which the BC line intersects with 1 atm line

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