Question 1

"A diamond is forever" is one of the most successful advertising slogans of all time. But is it true? For the reaction shown below, calculate the standard free energy change at 298K and determine whether or not a diamond is "forever". C(diamond)  → C(graphite)  Data: ΔHf°(diamond)  = 1.895 kJ/mol; S°(diamond)  = 2.337 J mol-1K-1; S°(graphite)  = 5.740 J mol-1K-1.

Accepted Answer

A)   ΔG° = 2.19 kJ; forever
B)   ΔG° = -1.90 kJ; not forever
C)   ΔG° = -2.90 kJ; not forever
D)   ΔG° = 1.90 kJ; forever
E)   ΔG° = < -1000 kJ; not foreverF) B) and D)
G) A) and C)

Question 2

For a reaction at equilibrium, ΔSuniv = 0.

Accepted Answer

A) True 
 B)False

Question 3

The formation constant for the reaction Ag+(aq)  + 2NH3(aq)  +(aq)  + 2NH3(aq)    Ag(NH3) 2+(aq)  Is Kf = 1.7 × 107 at 25°C. What is ΔG° at this temperature? A)  -1.5 kJ B)  -3.5 kJ C)  -18 kJ D)  -23 kJ E)  -41 kJ" class="answers-bank-image d-inline" rel="preload" > Ag(NH3) 2+(aq) 
Is Kf = 1.7 × 107 at 25°C. What is ΔG° at this temperature?

Accepted Answer

A)   -1.5 kJ
B)   -3.5 kJ
C)   -18 kJ
D)   -23 kJ
E)   -41 kJF) A) and D)
G) B) and C)

Question 4

Calculate ΔS° for the reaction 4Cr(s)  + 3O2(g)  → 2Cr2O3(s) 
Substance: Cr(s)  O2(g)  Cr2O3(s) 
S°(J/K·mol) : 23.77 205.138 81.2

Accepted Answer

A)   -548.1 J/K
B)   -147.7 J/K
C)   147.7 J/K
D)   310.1 J/K
E)   548.1 J/KF) A) and D)
G) C) and D)

Question 5

A reaction is proceeding toward equilibrium. At a certain stage, the concentrations of reactants and products are such that ΔG = ΔG°. What conclusion can reasonably be drawn about the reaction at this time?

Accepted Answer

A)   K > Q
B)   K 
C)   K = Q
D)   K = 1
E)   Q = 1F) C) and D)
G) A) and B)

Question 6

Consider the figure that shows ΔG° for a chemical process plotted against absolute temperature. From this plot, it is reasonable to conclude that  0, ΔS° > 0 B)  ΔH° > 0, ΔS°  0 D)  ΔH°

Accepted Answer

A)  ΔH° > 0, ΔS° > 0
B)   ΔH° > 0, ΔS° 
C)   ΔH°  0
D)   ΔH° 
E)   None of these choices are correct.F) A) and D)
G) B) and C)

Question 7

Given: H2O(l)  → H2O(g)  ΔH° = 40.7 kJ at 373K What is the entropy change in the system (ΔS)  when one mole of water vaporizes at 100°C and a pressure of one atmosphere?

Accepted Answer

A)   407 J/K
B)   -407 J/K
C)   109 J/K
D)   -109 J/K
E)   J/KF) A) and B)
G) A) and C)

Question 8

In a spontaneous process, the entropy of the system always increases.

Accepted Answer

A) True 
 B)False

Question 9

What is the free energy change, ΔG°, for the equilibrium between hydrogen iodide, hydrogen, and iodine at 453°C? Kc = 0.020 2HI(g)  c = 0.020 2HI(g)    H2(g)  + I2(g)  A)  6.4 kJ B)  8.8 kJ C)  15 kJ D)  19 kJ E)  24 kJ" class="answers-bank-image d-inline" rel="preload" > H2(g)  + I2(g)

Accepted Answer

A)   6.4 kJ
B)   8.8 kJ
C)   15 kJ
D)   19 kJ
E)   24 kJF) B) and D)
G) A) and E)

Question 10

Which relationship or statement best describes ΔS° for the following reaction? O3(g)  + NO(g)  → O2(g)  + NO2(g)

Accepted Answer

A)   ΔS° ≈ 0
B)   ΔS° 
C)   ΔS° > 0
D)   ΔS° = ΔH°/T
E)   More information is needed to make a reasonable prediction.F) A) and D)
G) A) and B)

Question 11

A sample of water is heated at a constant pressure of one atmosphere. Initially, the sample is ice at 260 K, and at the end the sample consists of steam at 400 K. In which of the following 5K temperature intervals would there be the greatest increase in the entropy of the sample?

Accepted Answer

A)   from 260 K to 265 K
B)   from 275 K to 280 K
C)   from 360 K to 365 K
D)   370 K to 375 K
E)   from 395 K to 400 KF) B) and C)
G) C) and E)

Question 12

Calculate ΔG° for the reaction of ammonia with fluorine. 2NH3(g)  + 5F2(g)  → N2F4(g)  + 6HF(g) 
Substance: NH3(g)  F2(g)  N2F4(g)  HF(g) 
ΔG°f (kJ/mol) : -16.4 0 9.9 -275.4

Accepted Answer

A)   179.1 kJ
B)   -179.1 kJ
C)   1539.7 kJ
D)   -1539.7 kJ
E)   None of these choices are correct.F) A) and C)
G) C) and D)

Question 13

In which one of the following pairs will the first system have a higher entropy than the second? Assume P and T are the same for each pair, unless stated otherwise.

Accepted Answer

A)   1 mole He(g) ; 1 mole Kr(g) 
B)   1 mole O2(g) ; 2 mole O(g) 
C)   1 mole CH4(g) ; 1 mole C2H6(g) 
D)   1 mole Xe(g)  at 1 atmosphere; 1 mole Xe(g)  at 0.5 atmosphere
E)   20 one-dollar bills distributed randomly among 20 people; 20 one-dollar bills distributed randomly among 10 peopleF) A) and D)
G) A) and C)

Question 14

In some spontaneous processes, the entropy of the surroundings decreases.

Accepted Answer

A) True 
 B)False

Question 15

For a process with ΔS < 0, which one of the following statements is correct?

Accepted Answer

A)   The process will definitely be spontaneous if ΔH 
B)   The process will be definitely be spontaneous if ΔH 
C)   The process can never be spontaneous.
D)   The process will definitely be spontaneous, regardless of ΔH.
E)   The process will definitely be spontaneous if ΔSsurr > 0.F) A) and B)
G) C) and D)

Question 16

Calculate ΔS° for the reaction 2Cl2(g)  + SO2(g)  → SOCl2(g)  + Cl2O(g) 
Substance: Cl2(g)  SO2(g)  SOCl2(g)  Cl2O(g) 
S°(J/K·mol) : 223.0 248.1 309.77 266.1

Accepted Answer

A)   -118.2 J/K
B)   -104.8 J/K
C)   104.8 J/K
D)   118.2 J/K
E)   1270.0 J/KF) B) and C)
G) B) and D)

Question 17

The second law of thermodynamics tells us that

Accepted Answer

A)   the entropy of the universe is constant.
B)   entropy is neither created nor destroyed.
C)   the universe proceeds toward a state of lower entropy.
D)   the universe proceeds toward a state of higher entropy.
E)   the universe cannot create entropy.F) A) and C)
G) C) and D)

Question 18

For a given reaction, a change in the pressure may result in a change in the sign of ΔG.

Accepted Answer

A) True 
 B)False

Question 19

Which of the following is true for pure oxygen gas, O2(g)  at 25°C?

Accepted Answer

A)   ΔH°f > 0
B)   ΔH°f 
C)   ΔG°f > 0
D)   ΔG°f 
E)   S° > 0F) C) and D)
G) A) and B)

Question 20

Calculate ΔS° for the combustion of propane. C3H8(g)  + 5O2(g)  → 3CO2(g)  + 4H2O(g) 
Substance: C3H8(g)  O2(g)  CO2(g)  H2O(g) 
S°(J/K·mol) : 269.9 205.138 213.74 18.825

Accepted Answer

A)   -100.9 J/K
B)   -72.5 J/K
C)   72.5 J/K
D)   100.9 J/K
E)   877.5 J/KF) D) and E)
G) All of the above

Exam 20: Thermodynamics Entropy, Free Energy, and Reaction Direction

A reaction is proceeding toward equilibrium. At a certain stage, the concentrations of reactants and products are such that ΔG = ΔG°. What conclusion can reasonably be drawn about the reaction at this time?

Correct Answer
verified

The formation constant for the reaction Ag⁺(aq) + 2NH₃(aq) Ag(NH₃) ²⁺(aq) Is K_f = 1.7 × 10⁷ at 25°C. What is ΔG° at this temperature?

Correct Answer
verified

Calculate ΔG° for the reaction of ammonia with fluorine. 2NH₃(g) + 5F₂(g) → N₂F₄(g) + 6HF(g) Substance: NH₃(g) F₂(g) N₂F₄(g) HF(g) ΔG°_f (kJ/mol) : -16.4 0 9.9 -275.4

Correct Answer
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Calculate ΔS° for the reaction 2Cl₂(g) + SO₂(g) → SOCl₂(g) + Cl₂O(g) Substance: Cl₂(g) SO₂(g) SOCl₂(g) Cl₂O(g) S°(J/K·mol) : 223.0 248.1 309.77 266.1

Correct Answer
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The second law of thermodynamics tells us that

Correct Answer
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What is the free energy change, ΔG°, for the equilibrium between hydrogen iodide, hydrogen, and iodine at 453°C? K_c = 0.020 2HI(g) H₂(g) + I₂(g)

Correct Answer
verified

Calculate ΔS° for the reaction 4Cr(s) + 3O₂(g) → 2Cr₂O₃(s) Substance: Cr(s) O₂(g) Cr₂O₃(s) S°(J/K·mol) : 23.77 205.138 81.2

Correct Answer
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In which one of the following pairs will the first system have a higher entropy than the second? Assume P and T are the same for each pair, unless stated otherwise.

Correct Answer
verified

Calculate ΔS° for the combustion of propane. C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g) Substance: C₃H₈(g) O₂(g) CO₂(g) H₂O(g) S°(J/K·mol) : 269.9 205.138 213.74 18.825

Correct Answer
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Correct Answer
verified

Given: H₂O(l) → H₂O(g) ΔH° = 40.7 kJ at 373K What is the entropy change in the system (ΔS) when one mole of water vaporizes at 100°C and a pressure of one atmosphere?

Correct Answer
verified

In a spontaneous process, the entropy of the system always increases.

Correct Answer
verified

Consider the figure that shows ΔG° for a chemical process plotted against absolute temperature. From this plot, it is reasonable to conclude that

Correct Answer
verified

Which of the following is true for pure oxygen gas, O₂(g) at 25°C?

Correct Answer
verified

In some spontaneous processes, the entropy of the surroundings decreases.

Correct Answer
verified

A sample of water is heated at a constant pressure of one atmosphere. Initially, the sample is ice at 260 K, and at the end the sample consists of steam at 400 K. In which of the following 5K temperature intervals would there be the greatest increase in the entropy of the sample?

Correct Answer
verified

For a given reaction, a change in the pressure may result in a change in the sign of ΔG.

Correct Answer
verified

For a process with ΔS < 0, which one of the following statements is correct?

Correct Answer
verified

Which relationship or statement best describes ΔS° for the following reaction? O₃(g) + NO(g) → O₂(g) + NO₂(g)

Correct Answer
verified

For a reaction at equilibrium, ΔS_univ = 0.

Correct Answer
verified

Exam 20: Thermodynamics Entropy, Free Energy, and Reaction Direction

A reaction is proceeding toward equilibrium. At a certain stage, the concentrations of reactants and products are such that ΔG = ΔG°. What conclusion can reasonably be drawn about the reaction at this time?

Correct AnswerverifiedShow Answer

The formation constant for the reaction Ag+(aq) + 2NH3(aq) Ag(NH3) 2+(aq) Is Kf = 1.7 × 107 at 25°C. What is ΔG° at this temperature?

Correct AnswerverifiedShow Answer

Calculate ΔG° for the reaction of ammonia with fluorine. 2NH3(g) + 5F2(g) → N2F4(g) + 6HF(g) Substance: NH3(g) F2(g) N2F4(g) HF(g) ΔG°f (kJ/mol) : -16.4 0 9.9 -275.4

Correct AnswerverifiedShow Answer

Calculate ΔS° for the reaction 2Cl2(g) + SO2(g) → SOCl2(g) + Cl2O(g) Substance: Cl2(g) SO2(g) SOCl2(g) Cl2O(g) S°(J/K·mol) : 223.0 248.1 309.77 266.1

Correct AnswerverifiedShow Answer

The second law of thermodynamics tells us that

Correct AnswerverifiedShow Answer

What is the free energy change, ΔG°, for the equilibrium between hydrogen iodide, hydrogen, and iodine at 453°C? Kc = 0.020 2HI(g) H2(g) + I2(g)

Correct AnswerverifiedShow Answer

Calculate ΔS° for the reaction 4Cr(s) + 3O2(g) → 2Cr2O3(s) Substance: Cr(s) O2(g) Cr2O3(s) S°(J/K·mol) : 23.77 205.138 81.2

Correct AnswerverifiedShow Answer

In which one of the following pairs will the first system have a higher entropy than the second? Assume P and T are the same for each pair, unless stated otherwise.

Correct AnswerverifiedShow Answer

Calculate ΔS° for the combustion of propane. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) Substance: C3H8(g) O2(g) CO2(g) H2O(g) S°(J/K·mol) : 269.9 205.138 213.74 18.825

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Given: H2O(l) → H2O(g) ΔH° = 40.7 kJ at 373K What is the entropy change in the system (ΔS) when one mole of water vaporizes at 100°C and a pressure of one atmosphere?

Correct AnswerverifiedShow Answer

In a spontaneous process, the entropy of the system always increases.

Correct AnswerverifiedShow Answer

Consider the figure that shows ΔG° for a chemical process plotted against absolute temperature. From this plot, it is reasonable to conclude that

Correct AnswerverifiedShow Answer

Which of the following is true for pure oxygen gas, O2(g) at 25°C?

Correct AnswerverifiedShow Answer

In some spontaneous processes, the entropy of the surroundings decreases.

Correct AnswerverifiedShow Answer

A sample of water is heated at a constant pressure of one atmosphere. Initially, the sample is ice at 260 K, and at the end the sample consists of steam at 400 K. In which of the following 5K temperature intervals would there be the greatest increase in the entropy of the sample?

Correct AnswerverifiedShow Answer

For a given reaction, a change in the pressure may result in a change in the sign of ΔG.

Correct AnswerverifiedShow Answer

For a process with ΔS < 0, which one of the following statements is correct?

Correct AnswerverifiedShow Answer

Which relationship or statement best describes ΔS° for the following reaction? O3(g) + NO(g) → O2(g) + NO2(g)

Correct AnswerverifiedShow Answer

For a reaction at equilibrium, ΔSuniv = 0.

Correct AnswerverifiedShow Answer

Correct Answer
verified

The formation constant for the reaction Ag⁺(aq) + 2NH₃(aq) Ag(NH₃) ²⁺(aq) Is K_f = 1.7 × 10⁷ at 25°C. What is ΔG° at this temperature?

Correct Answer
verified

Calculate ΔG° for the reaction of ammonia with fluorine. 2NH₃(g) + 5F₂(g) → N₂F₄(g) + 6HF(g) Substance: NH₃(g) F₂(g) N₂F₄(g) HF(g) ΔG°_f (kJ/mol) : -16.4 0 9.9 -275.4

Correct Answer
verified

Calculate ΔS° for the reaction 2Cl₂(g) + SO₂(g) → SOCl₂(g) + Cl₂O(g) Substance: Cl₂(g) SO₂(g) SOCl₂(g) Cl₂O(g) S°(J/K·mol) : 223.0 248.1 309.77 266.1

Correct Answer
verified

Correct Answer
verified

What is the free energy change, ΔG°, for the equilibrium between hydrogen iodide, hydrogen, and iodine at 453°C? K_c = 0.020 2HI(g) H₂(g) + I₂(g)

Correct Answer
verified

Calculate ΔS° for the reaction 4Cr(s) + 3O₂(g) → 2Cr₂O₃(s) Substance: Cr(s) O₂(g) Cr₂O₃(s) S°(J/K·mol) : 23.77 205.138 81.2

Correct Answer
verified

Correct Answer
verified

Calculate ΔS° for the combustion of propane. C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g) Substance: C₃H₈(g) O₂(g) CO₂(g) H₂O(g) S°(J/K·mol) : 269.9 205.138 213.74 18.825

Correct Answer
verified

Correct Answer
verified

Given: H₂O(l) → H₂O(g) ΔH° = 40.7 kJ at 373K What is the entropy change in the system (ΔS) when one mole of water vaporizes at 100°C and a pressure of one atmosphere?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Which of the following is true for pure oxygen gas, O₂(g) at 25°C?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Which relationship or statement best describes ΔS° for the following reaction? O₃(g) + NO(g) → O₂(g) + NO₂(g)

Correct Answer
verified

For a reaction at equilibrium, ΔS_univ = 0.

Correct Answer
verified