Download CHEM 102 FINAL EXAM WINTER 07-08

CHEM 102 Winter 07 Final Exam
On the answer sheet (scantron) write your Name, Student ID Number, and Recitation Section
Number. Choose the best (most correct) answer for each question AND ENTER IT ON YOUR
ANSWER SHEET.
Potentially useful information:
x=
− b ± b2 − 4 a c
2a
pH = pK a + log
[base]
[acid ]
ΔG° = ΔH° - T ΔS°
ΔG = ΔG° + RT ln Q
RT
E = E° −
ln Q
nF
R = 8.314 J mol-1 K-1
F = 96480 C/mol e1. Volatility of a liquid increases as temperature increases because
a. the molecules of the liquid decompose into lighter molecules.
b. an equilibrium between liquid and vapor is established.
c. the number of molecules with enough kinetic energy to escape from the liquid increases.
d. London forces increase as temperature increases.
ANSWER: c
2. Which group includes only exothermic processes?
a. freezing, vaporization, deposition
b. freezing, condensation, deposition
c. melting, condensation, deposition
d. melting, evaporation, sublimation
ANSWER: b
3. The temperature at point a is the
a. critical point.
b. triple point.
c. normal freezing point.
d. normal boiling point.
ANSWER: c
4. Which of the following can have cis and trans isomers?
a. CH3HC=CH2
b. BrHC=CHBr
c. (CH3)2C=CHCH3
d. H2C=CBr2
ANSWER: b
5. Classify the following molecule according to its functional group.
a. alcohol
b. alkane
c. carboxylic acid
d. ester
ANSWER: c
6. Which molecule is chiral?
a. 2,2-dibromobutane
b. 2-chlorobutane
c. 2-methyl-2-chlorobutane
d. 2-bromo-2-butene
ANSWER: b
7. Polyamides can be produced from
a. two monomers, one containing two amino groups, the other containing two carboxylic acid
groups.
b. one monomer, containing one amino and one carboxylic acid group.
c. one monomer, containing two amide groups.
d. either a or b above.
ANSWER: d
8. Which statement about a reaction rate is correct?
a. Its units vary depending on the order.
b. Its value generally decreases as temperature increases.
c. Its value depends on the concentration of the reactant(s).
d. Its value will not change when a catalyst is added.
ANSWER: c
9. The rate law for a given reaction is rate = k[reactant]2, with k = 2.64 × 10-4 M-1 min-1. If the
initial concentration is 0.0250 M, what is the initial rate, with the correct units?
a. 4.36 × 10-11 M min-1
b. 1.65 × 10-7 min-1
c. 6.60 × 10-6 M min-1
d. 1.65 × 10-7 M min-1
ANSWER: d
10. What is the overall order of the following reaction?
2H2(g) + O2(g) → 2H2O(g)
rate = k [H2] [O2]
a. 1
b. 2
c. 3
d. 5
ANSWER: b
11. What is the half-life for a first-order reaction with a rate constant of 0.834 s-1?
a. 0.417 s
b. 0.628 s
c. 0.831 s
d. 1.20 s
ANSWER: c
12. The species representing the combination of atoms or molecules at the top of the activation
energy barrier is called the
a. frequency factor.
b. activated complex.
c. catalytic converter.
d. reaction intermediate.
ANSWER: b
13. A weak acid is 5% ionized at equilibrium. Therefore we can say that the ionization reaction
is _____-favored, because _____.
a. product; the amount of products << the amount of reactants
b. reactant; the amount of products << the amount of reactants
c. reactant; the amount of products >> the amount of reactants
d. product; the amount of products >> the amount of reactants
ANSWER: b
14. Consider the equilibrium reaction
2N2(g) + O2(g) ⇌ 2N2O(g)
In a particular experiment, the equilibrium concentration of N2 is 1.17 atm, of O2, 2.27 atm,
and of N2O, 1.60 × 10-19 atm. What is the value of the equilibrium constant Kp?
a. 6.02 × 10-20
b. 8.24 × 10-39
c. 9.00 × 10-38
d. 1.27 × 10-18
ANSWER: b
15. To decide whether a reaction mixture is at equilibrium, a student determines the value of Q,
the reaction quotient, and finds that it is less than K. Therefore, the mixture is
a. at equilibrium, since there is as much reaction as required.
b. not at equilibrium, and will react to the right, to increase the amounts of products.
c. not at equilibrium, and will react to the left, to increase the amounts of reactants.
d. not at equilibrium, and will react to the right, to increase the amounts of reactants.
ANSWER: b
16. For the reaction
C(s) + CO2(g) ⇌ 2CO(g)
Kp = 4.1×103. A mixture contains some C(s), [CO] = 12.2 atm and [CO2] = 18.3 atm.
Therefore the system
at equilibrium, because
.
a. is not; the value of Q is 0.67
b. is; the value of Q is 0.67
c. is not; the value of Q is 8.1
d. is; the value of Q is 8.1
ANSWER: c
17. An endothermic reaction which results in an increase in moles of gas will be most productpressure and
temperature.
favored under conditions of
a. high; high
b. high; low
c. low; high
d. low; low
ANSWER: c
18. Solutions form when intermolecular forces can form between solvent molecules and solute
molecules or ions. What kind of intermolecular forces could be present when a solute
dissolves in a solvent?
a. dipole-dipole
b. London
c. hydrogen bonds
d. any of a, b, or c
ANSWER: d
19. If two liquids are miscible, they _____ because _____.
a. mix together; their intermolecular interactions are similar
b. do not mix together; their intermolecular interactions are similar
c. do not mix together; their intermolecular interactions are dissimilar
d. mix together; their intermolecular interactions are dissimilar
ANSWER: a
20. When a solution is supersaturated, the concentration of the solute is _____ the equilibrium
solubility, and _____ solute will dissolve.
a. less than; more
b. equal to; no more
c. greater than; more
d. greater than; no more
ANSWER: d
21. In this reaction
NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)
a. NH3 acts as a base and OH- as an acid.
b. H2O acts as an acid and OH- as a base.
c. H2O acts as a base and NH4+ as an acid.
d. NH3 acts as an acid and OH- as a base.
ANSWER: b
22. Which of the following would be the conjugate acid of CO32-?
a. HCl
b. H3O+
c. HCO3
d. H2CO3
ANSWERS: c
23. In a 1.2 M solution of HClO4, a strong acid, [H3O+] = _________, and [OH-] = _________.
a. 1.0 × 10-7 M; 1.0 × 10-7 M
b. 8.3 × 10-15 M; 1.2 M
c. 1.2 M; 8.3 × 10-15 M
d. 1.2 M; 1.2 M
ANSWER: c
24. The value of the ionization constant for a weak acid HA is 4.2 × 10-7. What is the pH of a
0.35 M solution of this acid?
a. 6.83
b. 6.38
c. 3.42
d. 2.96
ANSWER: c
25. Which acid, in combination with its conjugate base, would be the best choice to make a
buffer of pH = 4.20?
a. acetic acid (Ka = 1.8 × 10-5)
b. benzoic acid (Ka = 6.3 x 10-5)
c. formic acid (Ka = 1.8 × 10-4)
d. hydrofluoric (Ka = 7.2 × 10-4)
ANSWER: b
26. The Ksp expression for gold (III) chloride, AuCl3, is
a. [Au3+][Cl-].
b. [Au3+][Cl-]3.
c. [Au3+]3[Cl-].
d. 3[Au3+][Cl-].
ANSWER: b
27. Silver phosphate is less soluble in Na3PO4 than in water. Why?
a. A common ion displaces the solubility equilibrium towards the undissolved solute.
b. Some insoluble compounds are amphoteric.
c. The solubility of most salts increases as temperature increases.
d. Na3PO4 is more acidic than water.
ANSWER: a
28. What is the water solubility of PbI2 (Ksp = 8.4 10-9) in moles per liter?
a. 8.4 10-9 M
b. 1.9 10-7 M
c. 9.1 10-5 M
d. 1.3 10-3 M
ANSWER: d
29. Which has the lowest entropy at a given temperature?
a. O2(g)
b. H2O(g)
c. H2O(l)
d. H2O(s)
ANSWER: d
30. Calculate the ΔS° for the following process:
CH3CH2CH3(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
S°(CH3CH2CH3) = 269.9 J mol-1 K-1, S°(O2) = 205.138 J mol-1 K-1, S°(CO2) = 213.74 J mol-1
K-1, and S°(H2O) = 188.825 J mol-1 K-1
a. -326.55 J mol-1 K-1
b. 100.93 J mol-1 K-1
c. -100.93 J mol-1 K-1
d. -72.47 J mol-1 K-1
ANSWER: b
31. At what temperature does the following reaction shift from reactant-favored to productfavored? 2CO(g) + 2H2(g) → CH3CO2H(l)
ΔH° = -263.45 kJ mol-1, ΔS° = -496.92 J mol-1 K-1
a. 1.886 K
b. 0.5302 K
c. 1051 K
d. 530.2 K
ANSWER: d
32. Which statement is true for the following endothermic reaction?
MgCO3(s) → MgO(s) + CO2(g)
a. The reaction is spontaneous at all temperatures.
b. The reaction is never spontaneous.
c. The reaction is likely to be spontaneous at high temperatures.
d. The reaction is likely to be spontaneous at low temperatures.
ANSWER: c
33. Use the data given to calculate the value of Κ for the reaction at 5°C
Ag+(aq) + Cl-(aq) ⇌ AgCl(s)
ΔH°f = -65.45 kJ mol-1, ΔS° = -32.88 J K-1 mol-1
a. 1.9 x 1012
b. 3.8 x 1010
c. 5.7 x 109
d. 1.3 x 106
ANSWER: b
-
34. What is the correct balanced half reaction for the reduction of MnO4 to Mn2+ in acid?
a. MnO4 (aq) + 8H+(aq) + 8e → Mn2+(aq) + 4H2O(l)
b. MnO4 (aq) → Mn2+(aq) + 2e
c. MnO4 (aq) + 8H+(aq) + 5e → Mn2+(aq) + 4H2O(l)
d. MnO4 (aq) → Mn2+(aq) + 3e
ANSWER: c
35. If cadmium metal and the Fe(III) ion are mixed in aqueous solution, a solution containing
Cd(II) and Fe(II) results. The balanced equation for this process is
a. Cd(s) + Fe3+(aq) → Fe2+(aq) + Cd2+(aq).
b. Cd(s) + 2 Fe3+(aq) → 2Fe2+(aq) + Cd2+(aq).
c. 2Cd(s) + Fe3+(aq) → Fe2+(aq) + 2 Cd2+(aq).
d. 2Cd(s) + Fe3+(aq) → 2Fe2+(aq) + Cd2+(aq).
ANSWER: b
36. In a voltaic cell, oxidation occurs at the:
a. cathode
b. pentode
c. anode
d. diode
ANSWER: c
37. Consider an electrochemical cell as shown, with Zn in ZnSO4(aq) and Cu in CuSO4(aq), and
a salt bridge containing KNO3(aq). The overall chemical reaction is
Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s). Which statement is correct?
a. One mole of electrons is transferred in this reaction.
b. Copper is oxidized at the anode.
c. Electrons travel from the Zn to the Cu.
d. Zinc is reduced at the cathode.
ANSWER: c
38. What is E° for the following reaction?
Sn(s) + Cu2+(aq) → Sn2+(aq) + Cu(s).
-
where: Sn2+(aq) + 2e → Sn(s)
Cu2+(aq) + 2e → Cu(s)
a. 0.197 V
b. 0.477 V
c. - 0.477 V
d. 0.239 V
ANSWER: b
E° = - 0.140 V
E° = 0.337 V