Honors Chemistry Final Exam 2007 Study Guide



Honors Chemistry Final Exam 2011 Study Guide

General Concepts (Topics 1,2, etc)

• atoms, molecules, ions, moles

o Atom – the smallest particle on an element that still retains the chemical properties of that element. Contains a nucleus with neutrons and protons, electrons. Only one kind of atom makes up the substance, are building blocks of element.

o Molecules – The smallest particle/unit of a substance that retains the physical and chemical properties of that substance. Can be a group of atoms chemically bonded together. Exs.: He, Br2, H2O

o Ions – an atom or group of combined atoms that carries one or more electric charges. Occurs when an atom loses or gains electrons. A cation is when an atom loses one or more electrons, and an anion is when an atom gains one or more electrons.

o Moles – 1 mol = 6.02 x 1023 particles(this number is Avogadro’s number). There are 6.02 x 1023 amus in one gram.

• chemical formulas, writing chemical formulas

o a set of chemical symbols showing the elements present in a compound and their relative proportions, and in some cases the structure of the compound.(Also, see empirical formula , molecular formula.)

o Bond type

▪ Ionic compounds (opposite charge)– crisscross rule

[pic]

o Transition metal and nonmetal – given charge of trans. metal

▪ Transition metals – exception, have one charge

• Ag1+ Silver

• Zn2+ Zinc

• Cd2+ Cadmium

▪ 2 nonmetals = covalent(share e-) – 2nd element ends in

-ide, use prefixes when necessary

▪ polyatomic ions - When writing formulas using polyatomic ions, the rules do not change. Simply treat the polyatomic ion as if it were a single anion. If the cation is from category I, follow the rule for category I, from II, then II. The crisscross method does not change either.

Prefixes

1. mono

2. di

3. tri

4. tetra

5. penta

6. hexa

7. hepta

8. octa

9. nona

10. deca

o nomenclature – topic 4 study guide PDF (done)

• percent error (as we calculated in lab)

o Percent Error measures accuracy (measure of how closely your data agrees with the true value.).

▪ Formula: Percent Error = [pic]

• density units and calculations

o Mass per unit volume

o [pic]

o Density is most often measured in g/cm3 which is the same as g/mL. Can also be measured in kg/cm3.

▪ *Remember:

• 1 g= 1 mL

• 1 cm3 = 1 mL

• 1 L = 1 dm3

o Can use displacement

o The smaller the container, greater the density. If increase volume, density decreases by same factor.

• properties of metals and nonmetals

|Metals |Nonmetals |

|1. Good conductors of heat and electricity |1. Poor conductors of heat and electricity |

|(Silver and Copper are the best conductors) | |

|2. Malleable – can be hammered into sheets |2. Brittle |

|3. Ductile – can be pulled into wires | |

|4. Luster (shiny) |3. Dull |

|Solid at room temperature |4. State varies – Bromine (Br) is a liquid, other are solids and |

|(*except Hg – Mercury) |gases |

|Tend to lose/give up electrons (cation) |5. Tend to gain electrons (anion) |

▪ physical and chemical changes

o The changes matter undergoes are classified as either physical or chemical.

o Physical change – in general alters some aspect of the physical properties of matter, but the composition remains constant. The most often altered properties are form and state.

• Some examples of physical changes are breaking glass, cutting wood, melting ice, and magnetizing a piece of metal. In some cases, the process that caused the change can be easily reversed and the substance regains its original form. Water changing its state is a good example of physical changes. In the solid state, ice, water has a definite volume but takes the shape of the container. When water is heated above its boiling point, it changes to steam. Steam, a gas, has neither a definite size, because its fills the containing space, nor shape, because it takes the shape of the container.

Chemical changes – changes in the composition and structure of a substance. They are always accompanied by energy changes. If the energy released in the formation of a new structure exceeds the chemical energy in the original substances, energy will be given off, usually in the form of heat or light or both. This is called an exothermic reaction. If however the new structure needs to absorb more energy than is available from the reactants, the result is an endothermic reaction.

• Where is energy in the chemical reaction?

o Exothermic – energy released

o Endothermic – energy absorbed

• density of a gas at STP (Avogadro’s hypothesis)

o Equal to the MM(molar mass)/22.4 L

o Avogadro’s hypothesis – equal volumes of gases under identical conditions of temperature and pressure contain equal numbers of particles (atoms, molecules, ions, or electrons.)

• percent composition calculations – pg. 51

o Percent of a substance contained within a molecule

[pic]Be careful what element you are finding and the subscripts, etc.

• empirical and molecular formula calculations

o The simplest ratio formula is called the empirical formula, and the actual formula is true or molecular formula.

• oxidation state (valence numbers) – 174-178

o ** LEO says GER ---- Lose Electrons Oxidation and Gain Electrons Reduction

o Positive likely to lose electrons, negative atoms likely to gain electrons

o same as values for ions like 1+, usually written +1

The oxidation state of….

▪ An atom in an element is zero. Examples: O for Na(s), O2(g), and H(l)

▪ A monoatomic ion is the same as its charge. Examples: Na+1, Cl-1

▪ Oxygen is usually -2 in its compounds. Example: H2O where 2H(+1) + 1O(-2) = 0.

▪ : H2O, HCl, NH3 In binary compounds, the more electronegative element is assigned an oxidation number equal to its normal anion charge. Examples: PF3 : F=-1 and P2S3 ; S=-2

States of Matter (Topic 7)

• Heating curve - phase changes

• Graham’s law of Effusion – gases

[pic]

• sublimation (ex. dry ice) – solid to gas phase straight

• vapor pressure

o Created when liquids below their boiling points are evaporation. All liquids in a closed system, at all temps exert some vapor pressure

o High IMF, low vapor pressure and weaker/lower IMF, higher vapor pressure

o Evaporating a cooling process b/c molecules with higher KE escape, and temp. decreases as well since directly proportional

o Gasoline evaporates more readily than water, so its vapor pressure is higher and it is more volatile than water.

o Atmospheric pressure = vp + partial pressure of atmospheric molecules.

o When vapor press. = atmospheric pressure, boiling occurs

o Increase T, increase vp

• intermolecular forces (effect of boiling point and freezing point)

o *Network covalent > ionic > H-bond > London Dispersion > Noble Gases

o Higher the Dispersion valence e-‘s, the higher the melting point

• combined gas law:

**[pic]

• ideal gas law: PV = nRT ; R is constant given , T in Kelvin

• heat of fusion and vaporization – fusion is the amount of heat it takes a substance to move from solid to liquid phase – just pass through melting point. Vaporization is the amount of energy that must be added to move substance from liquid to gaseous phases.

Atomic Structure, Bonding and Periodic Properties (Tps 3, 5&6)

• electron configurations - done

• nuclear fission and fusion –

o Nuclear Fission

▪ o Splitting of a heavy nucleus into two or more lighter nuclei o Nuclear power plants provide some of our power to our houseas well as for air power and submarines. o Nuclear power safe as long as handled carefully

o Nuclear Fusion

▪ Fuse nuclei together o Have to overcome repelling force of two positive nuclei. o Process that takes space to power sun for last 4.5 billion years, as well as stars in universe for 15 million years

[pic][pic]

• Dalton, Rutherford, Thompson, Bohr

o Dalton’s 5 ideas about atoms – 1st atomic theory

o The electron was discovered by J.J Thomson

▪ Cathode ray tube, believed atoms must have positive particle to make atom neutral, plum pudding – positive pudding with negative chips/plums

o Rutherford’s gold foil experiment using alpha particles (helium nuclei) confirmed that there was mostly empty space between the nucleus and electrons

o Bohr

• quantum numbers – principal quantum number (n) – 1,2,3,4,5,etc. – refers to the average distance of the orbital =(probable location of e-) from the nucleus. 1 is closest to the nucleus and has the least energy. The numbers correspond to the orbits in the Bohr model. They are called energy levels.

• mass number and atomic number

• average atomic mass (from atomic mass of isotopes)

• electron energy for transitioning from higher energy level to ground state (i.e. n=3 to n=1) - energy released. Higher up it is excited and lower down it is in a lower energy state

• electronegativity, ionization energy, atomic radius (periodic trends)

• London dispersion forces (as related to molecular size and melting point within a family) –see above for melting point

o Are relatively weak forces, which exits among noble gas atoms and nonpolar molecules, they invoke an accidental dipole that induces a momentary dipole in a neighbor

o Dispersion forces (induced dipole – induced dipole or London dispersion forces): universal force of attraction between instantaneous dipoles. These forces are weak for small, low-molecular weight molecules, but large for heavy, long, and/or highly polarizable molecules. They usually dominate over dipole-dipole.

o Higher the Dispersion valence e-‘s, the higher the melting point

• molecular geometry (tetrahedral, Trigonal pyramidal, bent planar and linear shapes)

• organic molecules (carboxylic acids, alcohols and the alkane series)

o Be wary of (the organic molecules) carboxylic acids, alcohols, which are not bases such as CH2OH (alcohol)

Equations and Stoichiometry (Topic 4)

• balancing equations

• moles of gas as related to volume of a gas at STP or constant T and P

• problem solving using mole-mole ratios and mass-mass quantities

• calculations using molar concentrations (this appears often on the final exam) (find moles, grams, and volume)

o *Theoretical yield – the number you get in the end of a stoichiometry problem

o Not sure if have to know this, but percent yield is

Percentage Yield =     Mass of Actual Yield       x   100%

                  Mass of Theoretical Yield

and actual would be given.

• synthesis, decomposition, double replacement, single replacement chemical reactions combustion of a

hydrocarbon (can you write the chemical equation?)

o Halogens – if one by itself is above the other halogen, the reaction will take place

Solutions, Solubility and Solution Reactions (Topic 8)

• Solubility graph

• effects of temperature on solubility

• saturated solutions, unsaturated solutions and supersaturated solutions

• polar and nonpolar solvents

• freezing point depression and boiling point elevation calculations

• Acid/base theory – Arrhenius, Bronsted-Lowry

• pH calculations

• Electrolytes, weak and strong and nonelectrolytes

• Ksp and solubility

Energy, Rates and Equilibrium (Topics 8** and 9)

• exothermic and endothermic reactions

• changes in enthalpy (H) (heats of formation and Hess’s Law)

• changes in entropy (S)

• spontaneity and free energy (G)

• effects of a catalyst on the activation energy and in the pathway of a chemical reaction

• PE v reaction pathway graph for exo and endothermic reactions

• Equilibrium and rate of forward and reverse reaction

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