Chapter 18 Review
Student: ___________________________________________________________________________
1.
Which of these species has the highest entropy (S°) at 25°C?
A. CH3OH(l)
B. CO(g)
C. MgCO3(s)
D. H2O(l)
E. Ni(s)
2.
Arrange these compounds in order of increasing standard molar entropy at 25°C:
C3H8(g), C2H4(g), ZnS(s), and H2O(l).
A. ZnS(s) < H2O(l) < C3H8(g) < C2H4(g)
B. C2H4(g) < H2O(l) < C3H8(g) < NaCl(s)
C. ZnS(s) < C3H8(g) < C2H4(g) < H2O(l)
D. C3H8(g) < C2H4(g) < H2O(l) < ZnS(s)
E. ZnS(s) < H2O(l) < C2H4(g) < C3H8(g)
3.
Arrange the following substances in the order of increasing entropy at
25°C.
A. SiF4(g) < SiH4(g) < NaF(s) < HF(g) < Al(s)
B. HF(g) < Al(s) < NaF(s) < SiF4(g) < SiH4(g)
C. Al(s) < NaF(s) < HF(g) < SiH4(g) < SiF4(g)
D. Al(s) < HF(g) < NaF(s) < SiF4(g) < SiH4(g)
E. NaF(s) < Al(s) < HF(g) < SiF4(g) < SiH4(g)
4.
Which response includes all the following processes that are accompanied by an increase in entropy?
A. 1, 2, 3, 4
B. 1, 2
C. 2, 3, 4
D. 3, 4
E. 1, 4
5.
Which response includes all of the following processes that are accompanied by an increase in entropy?
A. 1, 2
B. 1, 3
C. 3, 4
D. 3
E. 2, 4
6.
Determine ΔS° for the reaction SO3(g) + H2O(l) → H2SO4(l).
A. 169.2 J/K·mol
B. 1343.2 J/K·mol
C. -169.2 J/K·mol
D. -29.4 J/K·mol
E. 29.4 J/K·mol
7.
Calculate ΔS° for the reaction SO2(s) + NO2(g) → SO3(g) + NO(g).
A. 53.6 J/K·mol
B. -53.6 J/K·mol
C. -22.2 J/K·mol
D. 474.8 J/K·mol
E. -474.8 J/K·mol
8.
The entropy change on vaporization (ΔSvap) of a compound or element is
A. always negative.
B. always positive.
C. sometimes positive and sometimes negative.
9.
A negative sign for ΔG indicates that, at constant T and P,
A. the reaction is exothermic.
B. the reaction is endothermic.
C. the reaction is fast.
D. the reaction is spontaneous.
E. ΔS must be > 0.
10. Calculate ΔG° for the reaction 3NO (g) + H O(l) → 2HNO (l) + NO(g).
2
2
3
A. 8.7 kJ/mol
B. 192 kJ/mol
C. -414 kJ/mol
D. -192 kJ/mol
E. -155 kJ/mol
11. Ozone (O3) in the atmosphere can react with nitric oxide (NO):
O3(g) + NO(g) → NO2(g) + O2(g).
Calculate the ΔG° for this reaction at 25°C. (ΔH° = -199 kJ/mol, ΔS° = -4.1 J/K·mol)
A. 1020 kJ/mol
B. -1.22 × 103 kJ/mol
C. 2.00 × 103 kJ/mol
D. -1.42 × 103 kJ/mol
E. -198 kJ/mol
12. Sodium carbonate can be made by heating sodium bicarbonate:
CO2(g) + H2O(g)
2NaHCO3(s) → Na2CO3(s) +
Given that ΔH° = 128.9 kJ/mol and ΔG° = 33.1 kJ/mol at 25°C, above what minimum temperature will
the reaction become spontaneous under standard state conditions?
A. 0.4 K
B. 3.9 K
C. 321 K
D. 401 K
E. 525 K
13. For the reaction H (g) + S(s) → H S(g), ΔH° = -20.2 kJ/mol and ΔS° = +43.1 J/K·mol. Which of these
2
2
statements is true?
A. The reaction is only spontaneous at low temperatures.
B. The reaction is spontaneous at all temperatures.
C. ΔG° becomes less favorable as temperature increases.
D. The reaction is spontaneous only at high temperatures.
E. The reaction is at equilibrium at 25°C under standard conditions.
14. The normal freezing point of ammonia is -78°C. Predict the signs of ΔH, ΔS, and ΔG for ammonia when
it freezes at -80°C and 1 atm: NH3(l) → NH3(s)
A. A
B. B
C. C
D. D
E. E
15. Hydrogen peroxide (H2O2) decomposes according to the equation
H2O2(l) → H2O(l) + (1/2)O2(g).
Calculate Kp for this reaction at 25°C. (ΔH° = -98.2 kJ/mol, ΔS° = 70.1 J/K·mol)
A. 1.3 × 10-21
B. 20.9
C. 3.46 × 1017
D. 7.5 × 1020
E. 8.6 × 104
16. At 1500°C the equilibrium constant for the reaction CO(g) + 2H2(g)
1.4 ×
Calculate ΔG° for this reaction at 1500°C.
A. 105 kJ/mol
B. 1.07 kJ/mol
C. -233 kJ/mol
D. -105 kJ/mol
E. 233 kJ/mol
CH3OH(g) has the value Kp =
10-7.
17. Calculate K at 298 K for the reaction SO (g) + NO (g) → SO (g) + NO(g).
p
2
2
3
A. 6.99 × 10-7
B. 5.71 × 10-8
C. 14.2
D. 475
E. 1.42 × 106
18. Determine the equilibrium constant Kp at 25°C for the reaction N2(g) + 3H2(g)
(
(NH3(g)) = -16.6 kJ/mol)
A. 1.52 × 10-6
B. 6.60 × 105
C. 8.28 × 10-2
D. 2.60
E. 13.4
2NH3(g)
19. K for the auto-ionization of water, H O(l) → H+(aq) + OH- (aq), is 1.0 × 10-14. What are the signs (+/-)
w
2
of ΔS° and ΔH° for the reaction at 25°C?
A. ΔS° = (+) and ΔH° = (+)
B. ΔS° = (+) and ΔH° = (-)
C. ΔS° = (-) and ΔH° = (+)
D. ΔS° = (-) and ΔH° = (-)
20. A spontaneous endothermic reaction always
A. causes the surroundings to get colder.
B. bursts into flame.
C. requires a spark to initiate it.
D. releases heat to the surroundings.
21. The reaction rates of many spontaneous reactions are actually very slow. Which of these statements is the
best explanation for this observation?
A. Kp for the reaction is less than one.
B. The activation energy of the reaction is large.
C. ΔG° for the reaction is positive.
D. Such reactions are endothermic.
E. The entropy change is negative.
22. Which species will have the greatest absolute entropy at 25°C?
A. Ne(g)
B. C2H2(g)
C. H2O(l)
D. C2H5OH(l)
E. C4H10(g)
23. Which species will have the lowest absolute entropy at 25°C?
A. C2H5OH(l)
B. C2H2(g)
C. C3H8(g)
D. C3H7OH(l)
E. C2H6(g)
24. Predict the sign of ΔS for the process N (g, 10 atm) → N (g, 1atm).
2
2
25. Predict the sign of ΔS for the reaction O (g) → 2O(g).
2
26. Predict the sign of ΔS for the reaction 6CO (g) + 6H O(g) → C H O (g) + 6O (g).
2
2
6 12 6
2
27. Is the reaction SiO (s) + Pb(s) → PbO (s) + Si(s) spontaneous?
2
2
(PbO2) = -217 kJ/mol
(SiO2) = -856 kJ/mol
28. For the reaction 3H2(g) + N2(g)
2NH3(g), Kc = 9.0 at 350°C. In what direction does this reaction
proceed at 350°C under standard state conditions?
29. How does the entropy change when a solid is melted?
30. How does the entropy change when a molecular solid is dissolved in water?
31. How does the entropy change when a gas is liquified?
32. Choose the substance with the higher entropy per mole at a given temperature: Br2(l) or Br2(g).
33. Choose the substance with the higher entropy per mole at a given temperature: CO2(g) or CO2(aq).
34. The entropy change ΔS° for the reaction NH Cl(s) → NH (g) + HCl(g) will be negative.
4
3
True False
Chapter 18 Review Key
1.
Which of these species has the highest entropy (S°) at 25°C?
A. CH3OH(l)
B. CO(g)
C. MgCO3(s)
D. H2O(l)
E. Ni(s)
Difficulty: Easy
Raymond - 018 Entropy... #1
2.
Arrange these compounds in order of increasing standard molar entropy at 25°C:
C3H8(g), C2H4(g), ZnS(s), and H2O(l).
A. ZnS(s) < H2O(l) < C3H8(g) < C2H4(g)
B. C2H4(g) < H2O(l) < C3H8(g) < NaCl(s)
C. ZnS(s) < C3H8(g) < C2H4(g) < H2O(l)
D. C3H8(g) < C2H4(g) < H2O(l) < ZnS(s)
E. ZnS(s) < H2O(l) < C2H4(g) < C3H8(g)
Difficulty: Medium
Raymond - 018 Entropy... #3
3.
Arrange the following substances in the order of increasing entropy at
25°C.
A. SiF4(g) < SiH4(g) < NaF(s) < HF(g) < Al(s)
B. HF(g) < Al(s) < NaF(s) < SiF4(g) < SiH4(g)
C. Al(s) < NaF(s) < HF(g) < SiH4(g) < SiF4(g)
D. Al(s) < HF(g) < NaF(s) < SiF4(g) < SiH4(g)
E. NaF(s) < Al(s) < HF(g) < SiF4(g) < SiH4(g)
Difficulty: Medium
Raymond - 018 Entropy... #4
4.
Which response includes all the following processes that are accompanied by an increase in entropy?
A.
B.
C.
D.
E.
1, 2, 3, 4
1, 2
2, 3, 4
3, 4
1, 4
Difficulty: Medium
Raymond - 018 Entropy... #5
5.
Which response includes all of the following processes that are accompanied by an increase in
entropy?
A.
B.
C.
D.
E.
1, 2
1, 3
3, 4
3
2, 4
Difficulty: Medium
Raymond - 018 Entropy... #6
6.
Determine ΔS° for the reaction SO3(g) + H2O(l) → H2SO4(l).
A.
B.
C.
D.
E.
169.2 J/K·mol
1343.2 J/K·mol
-169.2 J/K·mol
-29.4 J/K·mol
29.4 J/K·mol
Difficulty: Medium
Raymond - 018 Entropy... #9
7.
Calculate ΔS° for the reaction SO2(s) + NO2(g) → SO3(g) + NO(g).
A.
B.
C.
D.
E.
53.6 J/K·mol
-53.6 J/K·mol
-22.2 J/K·mol
474.8 J/K·mol
-474.8 J/K·mol
Difficulty: Medium
Raymond - 018 Entropy... #10
8.
The entropy change on vaporization (ΔSvap) of a compound or element is
A. always negative.
B. always positive.
C. sometimes positive and sometimes negative.
Difficulty: Easy
Raymond - 018 Entropy... #13
9.
A negative sign for ΔG indicates that, at constant T and P,
A. the reaction is exothermic.
B. the reaction is endothermic.
C. the reaction is fast.
D. the reaction is spontaneous.
E. ΔS must be > 0.
Difficulty: Easy
Raymond - 018 Entropy... #14
10.
Calculate ΔG° for the reaction 3NO2(g) + H2O(l) → 2HNO3(l) + NO(g).
A.
B.
C.
D.
E.
8.7 kJ/mol
192 kJ/mol
-414 kJ/mol
-192 kJ/mol
-155 kJ/mol
Difficulty: Medium
Raymond - 018 Entropy... #15
11.
Ozone (O3) in the atmosphere can react with nitric oxide (NO):
O3(g) + NO(g) → NO2(g) + O2(g).
Calculate the ΔG° for this reaction at 25°C. (ΔH° = -199 kJ/mol, ΔS° = -4.1 J/K·mol)
A. 1020 kJ/mol
B. -1.22 × 103 kJ/mol
C. 2.00 × 103 kJ/mol
D. -1.42 × 103 kJ/mol
E. -198 kJ/mol
Difficulty: Medium
Raymond - 018 Entropy... #16
12.
Sodium carbonate can be made by heating sodium bicarbonate:
CO2(g) + H2O(g)
2NaHCO3(s) → Na2CO3(s) +
Given that ΔH° = 128.9 kJ/mol and ΔG° = 33.1 kJ/mol at 25°C, above what minimum temperature
will the reaction become spontaneous under standard state conditions?
A. 0.4 K
B. 3.9 K
C. 321 K
D. 401 K
E. 525 K
Difficulty: Difficult
Raymond - 018 Entropy... #17
13.
For the reaction H2(g) + S(s) → H2S(g), ΔH° = -20.2 kJ/mol and ΔS° = +43.1 J/K·mol. Which of these
statements is true?
A. The reaction is only spontaneous at low temperatures.
B. The reaction is spontaneous at all temperatures.
C. ΔG° becomes less favorable as temperature increases.
D. The reaction is spontaneous only at high temperatures.
E. The reaction is at equilibrium at 25°C under standard conditions.
Difficulty: Medium
Raymond - 018 Entropy... #19
14.
The normal freezing point of ammonia is -78°C. Predict the signs of ΔH, ΔS, and ΔG for ammonia
when it freezes at -80°C and 1 atm: NH3(l) → NH3(s)
A.
B.
C.
D.
E.
A
B
C
D
E
Difficulty: Medium
Raymond - 018 Entropy... #20
15.
Hydrogen peroxide (H2O2) decomposes according to the equation
H2O2(l) → H2O(l) + (1/2)O2(g).
Calculate Kp for this reaction at 25°C. (ΔH° = -98.2 kJ/mol, ΔS° = 70.1 J/K·mol)
A. 1.3 × 10-21
B. 20.9
C. 3.46 × 1017
D. 7.5 × 1020
E. 8.6 × 104
Difficulty: Medium
Raymond - 018 Entropy... #21
16.
At 1500°C the equilibrium constant for the reaction CO(g) + 2H2(g)
= 1.4 × 10-7. Calculate ΔG° for this reaction at 1500°C.
A. 105 kJ/mol
B. 1.07 kJ/mol
C. -233 kJ/mol
D. -105 kJ/mol
E. 233 kJ/mol
CH3OH(g) has the value Kp
Difficulty: Medium
Raymond - 018 Entropy... #22
17.
Calculate Kp at 298 K for the reaction SO2(g) + NO2(g) → SO3(g) + NO(g).
A.
B.
C.
D.
E.
6.99 × 10-7
5.71 × 10-8
14.2
475
1.42 × 106
Difficulty: Medium
Raymond - 018 Entropy... #23
18.
Determine the equilibrium constant Kp at 25°C for the reaction N2(g) + 3H2(g)
(
(NH3(g)) = -16.6 kJ/mol)
A. 1.52 × 10-6
B. 6.60 × 105
C. 8.28 × 10-2
D. 2.60
E. 13.4
2NH3(g)
Difficulty: Medium
Raymond - 018 Entropy... #25
19.
Kw for the auto-ionization of water, H2O(l) → H+(aq) + OH- (aq), is 1.0 × 10-14. What are the signs
(+/-) of ΔS° and ΔH° for the reaction at 25°C?
A. ΔS° = (+) and ΔH° = (+)
B. ΔS° = (+) and ΔH° = (-)
C. ΔS° = (-) and ΔH° = (+)
D. ΔS° = (-) and ΔH° = (-)
Difficulty: Medium
Raymond - 018 Entropy... #31
20.
A spontaneous endothermic reaction always
A. causes the surroundings to get colder.
B. bursts into flame.
C. requires a spark to initiate it.
D. releases heat to the surroundings.
Difficulty: Easy
Raymond - 018 Entropy... #32
21.
The reaction rates of many spontaneous reactions are actually very slow. Which of these statements is
the best explanation for this observation?
A. Kp for the reaction is less than one.
B. The activation energy of the reaction is large.
C. ΔG° for the reaction is positive.
D. Such reactions are endothermic.
E. The entropy change is negative.
Difficulty: Easy
Raymond - 018 Entropy... #33
22.
Which species will have the greatest absolute entropy at 25°C?
A. Ne(g)
B. C2H2(g)
C. H2O(l)
D. C2H5OH(l)
E. C4H10(g)
Difficulty: Medium
Raymond - 018 Entropy... #45
23.
Which species will have the lowest absolute entropy at 25°C?
A. C2H5OH(l)
B. C2H2(g)
C. C3H8(g)
D. C3H7OH(l)
E. C2H6(g)
Difficulty: Medium
Raymond - 018 Entropy... #46
24.
Predict the sign of ΔS for the process N2(g, 10 atm) → N2(g, 1atm).
Positive
Difficulty: Medium
Raymond - 018 Entropy... #59
25.
Predict the sign of ΔS for the reaction O2(g) → 2O(g).
Positive
Difficulty: Medium
Raymond - 018 Entropy... #58
26.
Predict the sign of ΔS for the reaction 6CO2(g) + 6H2O(g) → C6H12O6(g) + 6O2(g).
Negative
Difficulty: Medium
Raymond - 018 Entropy... #60
27.
Is the reaction SiO2(s) + Pb(s) → PbO2(s) + Si(s) spontaneous?
(PbO2) = -217 kJ/mol
(SiO2) = -856 kJ/mol
No
Difficulty: Medium
Raymond - 018 Entropy... #62
28.
For the reaction 3H2(g) + N2(g)
2NH3(g), Kc = 9.0 at 350°C. In what direction does this reaction
proceed at 350°C under standard state conditions?
right to left
Difficulty: Medium
Raymond - 018 Entropy... #69
29.
How does the entropy change when a solid is melted?
increases
Difficulty: Easy
Raymond - 018 Entropy... #77
30.
How does the entropy change when a molecular solid is dissolved in water?
increases
Difficulty: Easy
Raymond - 018 Entropy... #79
31.
How does the entropy change when a gas is liquified?
decreases
Difficulty: Easy
Raymond - 018 Entropy... #80
32.
Choose the substance with the higher entropy per mole at a given temperature: Br2(l) or Br2(g).
Br2(g)
Difficulty: Medium
Raymond - 018 Entropy... #82
33.
Choose the substance with the higher entropy per mole at a given temperature: CO2(g) or
CO2(aq).
CO2(g)
Difficulty: Medium
Raymond - 018 Entropy... #84
34.
The entropy change ΔS° for the reaction NH4Cl(s) → NH3(g) + HCl(g) will be negative.
FALSE
Difficulty: Easy
Raymond - 018 Entropy... #89
Chapter 18 Review Summary
Category
Difficulty: Difficult
Difficulty: Easy
Difficulty: Medium
Raymond - 018 Entropy...
# of Questions
1
9
24
34