| Information: | |
| gas
constant: R = 0.08206 L·atm/mole·K
= 8.314 J/mole·K Avogadro's number: NA = 6.022 ´ 1023/mol Q-dependence of free energy change: DG = DGo + RT ln(Q) normal freezing point of water: 0°C = 273K water ionization constant (25°C): Kw = 1.00 ´ 10-14 pressure: 1 atm = 760 mmHg = 760 torr log conversion: ln(x) = 2.303 log(x) quadratic equation: ax2 + bx + c = 0, |
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Multiple choice: select one answer for each question:
1. The pH of a buffer solution that consists of 0.58 M boric acid (H3BO3 , pKa = 9.24) and 0.27 M sodium borate (NaH2BO3) is:
| a) |
8.70 |
|
| b) | 9.34 | |
| c) | 8.46 | |
| d) | 9.57 | |
| e) | 8.91 | |
2. The best criterion for the spontaneity of a chemical reaction at constant T and P is the sign of
| a) | DH | |
| b) |
DH° |
|
| c) | TDS | |
| d) | DG | |
| e) | DG° | |
3.
Find
DG°
for the reaction at 298K: I2(g) + Cl2(g) 
2
ICl(g), DH°
= -26.9 kJ,
DS°
= 11.3 J/K
| a) | 102 kJ | |
| b) | -30.3 kJ | |
| c) | 50.6 kJ | |
| d) | +18.4 kJ | |
| e) | -50.6 kJ | |
4. The solubility of PbSO4 (Ksp = 1 ´ 10-8 ) in water is
| a) | 1 ´ 10-4 M | ||
| b) | 1 ´ 10-7 M | ||
| c) | 1 ´ 10-5 M | ||
| d) | 1 ´ 10-8 M | ||
| e) | 1 ´ 10-6 M | ||
5. In which of the following reactions will DS° be positive?
| 1.
N2O4(g) ®
2NO2(g) 2. CaO(s) + CO2(g) ® CaCO3(s) 3. sublimation of CO2 |
||
| a) | 1 only | |
| b) | 2 only | |
| c) | 1 and 2 only | |
| d) | 1 and 3 only | |
| e) | 1, 2 and 3 | |
6. The equation associated with Kf for the complex ion Ag(NH3)2+ is
| a) | Ag(NH3)2+(aq)
Ag+(aq)
+ 2NH3(aq) |
|
| b) | Ag+(aq)
+ 2NH3(aq)
Ag(NH3)2+(aq) |
|
| c) | Ag(NH3)2+(aq)
Ag+(g)
+ 2NH3(g) |
|
| d) | Ag+(g)
+ 2NH3(g) Ag(NH3)2+(aq) |
|
| e) | Ag+(aq)
+ N2(g) + 3H2(g) Ag(NH3)2+(aq) |
|
7. The pH after mixing 0.00020 mole of HCl and 0.00018 mole of NaOH in 1.000 L of solution is:
| a) | 4.70 | |
| b) | 5.00 | |
| c) | 5.30 | |
| d) | 5.60 | |
| e) | 9.00 | |
8. A chemical equilibrium that favors reactants at high temperature and products at low temperature has
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|
||
| a) | DHo > 0, DSo > 0 | |
| b) | DHo > 0, DSo < 0 | |
| c) | DHo < 0, DSo < 0 | |
| d) | DHo < 0, DSo > 0 | |
| e) | none of the above | |
9. Calculate the equilibrium constant Kp for the reaction at 500K:
|
|
Cu(s)
+ H2O(g) CuO(s)
+ H2(g),
DG°500K
= 110.6 kJ |
|
| a) | 2.4 ´ 10-13 | |
| b) | 5.6 ´ 10-12 | |
| c) | 0.97 | |
| d) | 3.5 ´ 10-11 | |
| e) | 2.8 ´ 10-12 | |
10. Calculate the solubility of Cu(OH)2 (Ksp =1 ´10-20) in a solution buffered at pH = 6.00.
| a) | 1 ´10-6 M | |
| b) | 1 ´10-14 M | |
| c) | 1 ´10-8 M | |
| d) | 1 ´10-4 M | |
| e) | 1 ´10-10 M | |
| Questions 11-15: Titrate 64 mL of 0.200M weak acid HA (Ka = 1 ´ 10-8 ) with 0.200M NaOH. |
11. The equilibrium concentrations at the equivalence point satisfy
| a) | [HA] < [A- ] | |
| b) | [HA] = [A- ] | |
| c) | [HA] > [A- ] | |
12. The volume of NaOH needed to reach the buffer point is
| a) | 64 mL | |
| b) | 16 mL | |
| c) | 32 mL | |
| d) | 48 mL | |
| e) | 72 mL | |
13. The pH at the buffer point is
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||
| a) | 4 | |
| b) | 7 | |
| c) | 9 | |
| d) | 6 | |
| e) | 8 | |
14. At pH = 7 the quotient [A- ] / [HA] is
| a) | 0.01 | |
| b) | 0.10 | |
| c) | 1 | |
| d) | 10 | |
| e) | 100 | |
15. The pH at the equivalence point satisfies
| a) | pH < 7 | ||
| b) | pH = 7 | ||
| c) | pH > 7 | ||
| Questions 16-20: Titrate 60 mL of 0.50 M acid H2A (Ka1 = 1 ´ 10-3 , Ka2 = 1 ´ 10-9 ) with 0.50 M NaOH . |
16. The volume of NaOH needed to reach the first equivalence point is:
| a) | 90 mL | |
| b) | 30 mL | |
| c) | 75 mL | |
| d) | 60 mL | |
| e) | 45 mL | |
17. The pH at the first equivalence point is:
| a) | 7 | |
| b) | 9 | |
| c) | 3 | |
| d) | 8 | |
| e) | 6 | |
18. Equilibrium concentrations at the first equivalence point satisfy:
| a) | [HA- ] > [A2- ] > [H2A] | |
| b) | [H2A] = [HA- ] > [A2- ] | |
| c) | [HA- ] > [A2- ] = [H2A] | |
| d) | [A2- ] = [HA- ] > [H2A] | |
| e) | [HA- ] > [H2A] > [A2- ] | |
19. Equilibrium concentrations at pH = 4 satisfy:
| a) | [HA- ] > [H2A] > [A2- ] | |
| b) | [A2- ] = [HA- ] > [H2A] | |
| c) | [HA- ] > [A2- ] = [H2A] | |
| d) | [H2A] = [HA- ] > [A2- ] | |
| e) | [HA- ] > [A2- ] > [H2A] | |
20. Equilibrium concentrations at the second buffer point satisfy:
| a) | [A2- ] > [HA- ] > [H2A] | |
| b) | [A2- ] = [HA- ] > [H2A] | |
| c) | [HA- ] > [H2A] > [A2- ] | |
| d) | [HA- ] > [A2- ] = [H2A] | |
| e) | [H2A] = [HA- ] > [A2- ] | |
| KEY: |  |