Multiple Choice
Identify the
letter of the choice that best completes the statement or answers the question.
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1.
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Which
reaction is likely to have a negative change in entropy? a. | 2
NH3(g) →
N2(g) + 3 H2(g) | b. | CaCO3(s) →CaO(s) + CO2(g) | c. | NaCl(s)
→
Na+(aq) + Cl-(aq) | d. | N2O4(g)
→ 2
NO2(g) | e. | 2 CO(g) → C(s) + O2(g) | | |
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2.
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Calculate the standard entropy change for the combustion of methanol at 25
°C.
2 CH3OH(l) + 3
O2(g) → 2 CO2(g) + 4 H2O(g)
Species | S° (J/K×mol) | CH 3
OH (l) | 127.2 | O 2
(g) | 205.1 | CO 2
(g) | 213.7 | H 2
O(g) | 188.8 | | |
a. | -2052.3
J/K | b. | -312.9
J/K | c. | +70.2
J/K | d. | +312.9
J/K | e. | +2052.3
J/K | | |
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3.
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Calculate the standard entropy change for the following
reaction,
2 HgO(s) → 2 Hg(l) + O2(g)
given
S°[HgO] = 70.3
J/K·mol, S°[ Hg(l)] =76.0 J/K·mol, and S°[O2(g)] = 205.1 J/K·mol. a. | -216.5
J/K | b. | +210.8
J/K | c. | +216.5
J/K | d. | +351.4
J/K | e. | +497.7
J/K | | |
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4.
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The standard entropy of formation of PCl3(g) is -33.2 J/K·mol.
1/4 P4(s) + 3/2 Cl2(g)
→
PCl3(g)
Calculate the standard molar
entropy of PCl3(g) given S°[P4(s)] = 41.1 J/K·mol and S°[Cl2(g)] = 223.1 J/K·mol. a. | -378.1
J/K·mol | b. | -297.4 J/K·mol | c. | +212.2
J/K·mol | d. | +231.0 J/K·mol | e. | +311.7
J/K·mol | | |
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5.
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For
the following reaction at 25.0 °C,
2 C(s) +
O2(g) → 2 CO(g)
calculate 
given  = 179.1 J/K and  = -221.1 kJ. a. | -9023
J/K | b. | -562.3
J/K | c. | -167.7
J/K | d. | +170.2
J/K | e. | +920.7
J/K | | |
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6.
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Use
the following thermodynamic data
Species |
Δ H° (kJ/mol) | S° (J/K·mol) | H 2
O 2 (l) | -187.78 | 109.6 | H 2
O(l) | -285.83 | 69.91 | O2
(g) | 0 | 205.14 | | | |
to calculate 
for the decomposition of hydrogen peroxide at 25.0 °C.
2 H2O2(l) → 2 H2O(l) + O2(g)
a. | -783.5
J/K | b. | -531.9
J/K | c. | +494.2
J/K | d. | +783.5
J/K | e. | +3741
J/K | | |
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7.
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Predict the signs of ΔH and ΔS for the condensation of steam at 85 °C. a. |
ΔH < 0 and ΔS < 0 | b. |
ΔH < 0 and ΔS > 0 | c. |
ΔH > 0 and ΔS < 0 | d. |
ΔH > 0 and ΔS > 0 | e. |
ΔH = 0 and ΔS < 0 | | |
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8.
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Hydrogen gas is a non-polluting fuel. Predict the signs of ΔH,
ΔS, and
ΔG for the
combustion of hydrogen gas at 150 °C.
2
H2(g) + O2(g) → 2 H2O(g)
a. |
ΔH < 0,
ΔS > 0,
ΔG < 0 | b. |
ΔH < 0,
ΔS < 0,
ΔG < 0 | c. |
ΔH < 0,ΔS > 0,
ΔG < 0 | d. |
ΔH > 0,
ΔS < 0,
ΔG < 0 | e. |
ΔH > 0,
ΔS < 0,ΔG > 0 | | |
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9.
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Diluting concentrated sulfuric acid with water can be dangerous. The temperature of
the solution can increase rapidly. What are the signs of ΔH,
ΔS, and ΔG for this process? a. |
ΔH < 0, ΔS > 0, ΔG < 0 | b. |
ΔH < 0, ΔS < 0, ΔG < 0 | c. |
ΔH < 0, ΔS > 0, ΔG > 0 | d. |
ΔH > 0, ΔS > 0, ΔG < 0 | e. |
ΔH > 0, ΔS < 0, ΔG > 0 | | |
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10.
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At
what temperatures will a reaction be spontaneous if
ΔH = +158 kJ and
ΔS = +411 J/K? a. | All temperatures
below 384 K | b. | Temperatures between 158 K and 411 K | c. | All temperatures
above 384 K | d. | The reaction will be spontaneous at any
temperature. | e. | The reaction will never be
spontaneous. | | |
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11.
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At
what temperatures will a reaction be spontaneous if ΔH = -76.0 kJ and ΔS = +231 J/K? a. | All temperatures
below 329 K | b. | Temperatures between 0 K and 231 K | c. | All temperatures
above 329 K | d. | The reaction will be spontaneous at any
temperature. | e. | The reaction will never be
spontaneous. | | |
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12.
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For a
reaction,
ΔH = +62.9
kJ andΔS =
+132.9 J/K. At what temperature will
ΔG = 0.00 kJ? a. | 2.11 K | b. | 70.0
K | c. | 473
K | d. | 8.36
´ 106
K | e. | DG is
greater than 0.00 kJ at any temperature. | | |
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13.
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Calculate 
for the reaction below at 25.0 °C
2
H2O(g) + S(s) → 2 H2S(g) + O2(g)
given  =
+442.4 kJ and  = +206.9 J/K. a. | +380.7
kJ | b. | +504.1
kJ | c. | +649.3
kJ | d. | +1277.7
kJ | e. | +6.125
´ 104
kJ | | |
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14.
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Calculate  for the reaction below at 25.0°C
CO(g) +
H2O(l)
→
H2(g) + CO2(g)
given  [CO(g)] = -137.2 kJ/mol,  [H2O(l)] = -237.2
kJ/mol,  [H2(g)] = 0.0 kJ/mol, and  [CO2(g)] = -394.4
kJ/mol. a. | -768.8
kJ | b. | -294.4
kJ | c. | -20.0
kJ | d. | +20.0
kJ | e. | +768.8
kJ | | |
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15.
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The
 for the following reaction is +70.9
kJ.
SO3(g) → SO2(g) + 
O2(g)
Given  [
SO3(g)] = -371.0 kJ/mol, calculate 
[SO2(g)]. a. | -300.1 kJ/mol | b. |
-5.23 kJ/mol | c. | +5.23 kJ/mol | d. |
+300.1 kJ/mol | e. | +441.9 kJ/mol | | |
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16.
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Calculate DG° for the reaction below at 25.0 °C.
P4(s) + 6 H2O(l)
→ 4
H3PO4(l)
Species | 
(kJ/mol) | 
(J/K· mol) | P 4
(s) | 0 | 22.80 | H 2
O(l) | -285.8 | 69.95 | H3
PO 4 (l) | -1279.0 | 110.5 | | | |
a. | -993.2 kJ | b. | -998.5
kJ | c. | -3137
kJ | d. | -3252
kJ | e. | -3401
kJ | | |
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17.
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Calculate ΔG° for the reaction below at 125 °C.
C2H5OH(g) + 3 O2(g)
→ 2
CO2(g) + 3 H2O(g)
Species | 
(kJ/mol) | 
(J/K· mol) | C 2
H 5 OH(g) | -235.3 | 282.7 | O 2
(g) | 0 | 205.1 | CO 2
(g) | -393.5 | 213.7 | H 2
O(g) | -241.8 | 188.8 | | | |
a. | -366.0 kJ | b. | -1277.1
kJ | c. | -1289.1
kJ | d. | -1315.2
kJ | e. | -3.94
´ 104
kJ | | |
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18.
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Estimate the boiling point of carbon tetrachloride given the following thermodynamic
parameters.
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CCl 4
(l) | CCl 4 (g) |  (kJ/mol) | -128.4 | -96.0 |  (
J/K·mol) | 214.4 | 309.7 |  (kJ/mol) | -57.6 | -53.6 | | | |
a. | -272
°C | b. | 25 °C | c. | 67 °C | d. | 69 °C | e. | 109 °C | | |
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19.
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For a
chemical reaction, if
ΔG° = 0, then a. | K > 1 | b. | K =
0 | c. | K <
1 | d. | K <
0 | e. | K =
1 | | |
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20.
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All
of the following relationships are true EXCEPT a. | | b. |  = -RT ln
(K) | c. | | d. | DH =  +
RT ln (K) | e. |  =
-T | | |
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21.
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The
standard free energy change for a chemical reaction is -18.3 kJ/mole. What is the equilibrium
constant for the reaction at 87 °C? (R = 8.314 J/K·mol) a. | 2.2
×10-3 | b. | 1.0 | c. | 6.1 | d. | 4.5 ×
102 | e. | 1.3
×
106 | | |
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22.
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The
standard free energy change for the formation of N2H4(l) from elements
is +149 kJ/mol at 25 °C. What is the equilibrium constant for the reaction? (R =
8.314 J/K·mol) a. | 7
ｘ10-61 | b. | 8
ｘ
10-27 | c. | 1 | d. | 1
ｘ 1026 | e. | 1
ｘ
1060 | | |
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23.
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What
is the equilibrium constant for reaction below at 25 °C? (R = 8.314 J/K·mol)
2 H2O2(l)
⇌
2 H2O(l) + O2(g)
given  [H2O2(l) ] = -120.3 kJ/mol,  [H2O(l) ] = -237.1 kJ/mol, and  [O2(g)] = 0.0 kJ/mol. a. | 5
ｘ10-95 | b. | 1
ｘ10-41 | c. | 1 | d. | 3
ｘ 1020 | e. | 9
ｘ1040 | | |
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24.
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The
equilibrium constant for a reaction at 25 °C is 4.7 x 10-8. What is DG°? (R = 8.314 J/K·mol) a. | +1.52
kJ | b. | +3.51
kJ | c. | +6.81
kJ | d. | +18.2
kJ | e. | +41.8
kJ | | |
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25.
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Calculate ΔG° for the following reaction at 425 °C,
H2(g) + I2(g)
⇌
2
HI(g)
given K = 56. (R = 8.314
J/K·mol) a. | -23.4
kJ | b. | -14.2
kJ | c. | -10.1
kJ | d. | -6.18
kJ | e. | +14.2
kJ | | |
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