Question 1

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

Accepted Answer

A)  Δ H° > 0, Δ S° > 0
B)  Δ H° > 0, Δ S° 
C)  Δ H°  0
D)  Δ H° 
E)  None of these choices are correct.F) B) and D)
G) None of the above

Question 2

Hydrogen sulfide decomposes according to the following reaction 2H2S(g)  → 2H2(g)  + S2(g) 
For this reaction at 298K ΔS° = 78.1 J/K, ΔH° = 169.4 kJ, and ΔG° = 146.1 kJ. What is the value of ΔG° at 900 K?

Accepted Answer

A)  −69881 kJ
B)  48.4 kJ
C)  99.1 kJ
D)  240 kJ
E)  441 kJF) B) and E)
G) A) and B)

Question 3

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl3(g)  + 1.5H2(g)  → B(s)  + 3HCl(g) 
Calculate ΔG° for the reaction.
3(g)  + 1.5H2(g)  → B(s)  + 3HCl(g)  Calculate ΔG° for the reaction.   A) −293.4 kJ B) 293.4 kJ C) −102.8 kJ D) 102.8 kJ E) None of these choices are correct." class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  −293.4 kJ
B)  293.4 kJ
C)  −102.8 kJ
D)  102.8 kJ
E)  None of these choices are correct.F) None of the above
G) C) and E)

Question 4

Sulfuryl dichloride is formed when sulfur dioxide reacts with chlorine. The data refer to 298 K. SO2(g)  + Cl2(g)  → SO2Cl2(g) 
2(g)  + Cl2(g)  → SO2Cl2(g)    What is the value of ΔG° for this reaction at 600 K? A) −162.8 kJ B) −40.1 kJ C) −28.4 kJ D) 28.4 kJ E) 162.8 kJ" class="answers-bank-image d-inline" rel="preload" > What is the value of ΔG° for this reaction at 600 K?

Accepted Answer

A)  −162.8 kJ
B)  −40.1 kJ
C)  −28.4 kJ
D)  28.4 kJ
E)  162.8 kJF) A) and B)
G) A) and C)

Question 5

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?

Accepted Answer

A)  Δ S° > 0, Δ H° > 0
B)  Δ S° > 0, Δ H° 
C)  Δ S° 
D)  Δ S°  0
E)  It is not possible for a reaction to be spontaneous at all temperatures.F) C) and E)
G) B) and D) B

Question 6

Calculate the equilibrium constant at 25°C for the reaction of methane with water to form carbon dioxide and hydrogen. The data refer to 25°C. CH4(g)  + 2H2O(g)  ⇄ CO2(g)  + 4H2(g) 
4(g)  + 2H2O(g)  ⇄ CO2(g)  + 4H2(g)    A) 8.2 × 10 19 B) 0.96 C) 0.58 D) 1.2 × 10 −20 E) 1.4 × 10 −46" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  8.2 × 10 19
B)  0.96
C)  0.58
D)  1.2 × 10 −20
E)  1.4 × 10 −46F) A) and C)
G) C) and E)

Question 7

Given: H2O(l)  → H2O(s)  ΔH° = −6.02 kJ at 273K Calculate the entropy change of the surroundings (ΔSsurr)  when one mole of water freezes at 0°C and a pressure of one atmosphere.

Accepted Answer

A)  22.1 J/K
B)  −22.1 J/K
C)  397 J/K
D)  −397 J/K
E)  0.022 J/KF) A) and C)
G) A) and B)

Question 8

As a chemical reaction proceeds toward equilibrium, the free energy of the system decreases.

Accepted Answer

A) True 
 B)False

Question 9

Consider the following quantities used in thermodynamics: E, H, q, w, S, G. How many of them are state functions?

Accepted Answer

A)  0
B)  1
C)  2
D)  3
E)  4F) A) and B)
G) A) and D)

Question 10

"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)  Δ G° = 2.19 kJ; forever
B)  Δ G° = −1.90 kJ; not forever
C)  Δ G° = −2.90 kJ; not forever
D)  Δ G° = 1.90 kJ; forever
E)  Δ G° = < −1000 kJ; not foreverF) C) and D)
G) All of the above C

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 E)
G) C) and D)

Question 12

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

Accepted Answer

A)  Δ H° f > 0
B)  Δ H° f 
C)  Δ G° f > 0
D)  Δ G° f 
E)  S° > 0F) A) and B)
G) C) and E)

Question 13

In which one of these pairs will the entropy of the first substance be greater than that of the second? Assume P and T are the same for each pair, unless stated otherwise.

Accepted Answer

A)  1 mole of F 2( g) ; 1 mole of Cl 2( g) 
B)  1 mole of I 2( s) ; 1 mole of I 2( g) 
C)  1 mole of CaCO 3( s) ; 1 mole of CaO( s) plus 1 mole of CO 2( g) 
D)  1 mole of H 2( g) at 25°C; 1 mole of H 2( g) at 50°C
E)  1 mole of O 3( g) ; 1 mole of O 2( g) F) A) and E)
G) B) and E)

Question 14

Which of the following values is based on the Third Law of Thermodynamics?

Accepted Answer

A)  Δ H° f = 0 for Al( s) at 298 K
B)  Δ G° f = 0 for H 2( g) at 298 K
C)  S° = 51.446 J/(mol·K) for Na( s) at 298 K
D)  q sys 2O( l) → H 2O(s) at 0°C
E)  None of these choices are correct.F) A) and B)
G) All of the above

Question 15

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)

Accepted Answer

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

Question 16

You are given pure samples of ammonia, NH3(g) , and nitrogen trifluoride, NF3(g) . What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

A)  S° ammonia > S° nitrogen trifluoride
B)  S° ammonia nitrogen trifluoride
C)  S° ammonia ≈ S° nitrogen trifluoride
D)  Other conditions need to be specified before a reliable prediction can be made.
E)  Even if more conditions are specified, a reliable prediction cannot be made.F) A) and C)
G) D) and E)

Question 17

Which one of the following phase changes decreases the entropy of the system?

Accepted Answer

A)  Melting
B)  Heating a gas
C)  Vaporization
D)  Condensation
E)  SublimationF) A) and E)
G) A) and B)

Question 18

The term microstate refers to the energy state of a single molecule in a system of many molecules.

Accepted Answer

A) True 
 B)False  False

Question 19

A reaction has ΔG = 10.0 kJ and ΔG° = 15.0 kJ at a temperature of 50°C. Calculate the value of the reaction quotient −5 C) 1.1 × 10 4 D) 6.4 E) 6.0 × 10 −6" class="answers-bank-image d-inline" rel="preload" > under these conditions.

Accepted Answer

A)  0.16
B)  9.1 × 10 −5
C)  1.1 × 10 4
D)  6.4
E)  6.0 × 10 −6F) C) and D)
G) A) and B)

Question 20

Which of the following should have the greatest molar entropy at 298 K?

Accepted Answer

A)  CH 4( g) 
B)  H 2O( l) 
C)  NaCl( s) 
D)  N 2O 4( g) 
E)  H 2( g) F) All of the above
G) None of the above

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

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

Hydrogen sulfide decomposes according to the following reaction 2H₂S(g) → 2H₂(g) + S₂(g) For this reaction at 298K ΔS° = 78.1 J/K, ΔH° = 169.4 kJ, and ΔG° = 146.1 kJ. What is the value of ΔG° at 900 K?

Correct Answer
verified

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl₃(g) + 1.5H₂(g) → B(s) + 3HCl(g) Calculate ΔG° for the reaction.

Correct Answer
verified

Sulfuryl dichloride is formed when sulfur dioxide reacts with chlorine. The data refer to 298 K. SO₂(g) + Cl₂(g) → SO₂Cl₂(g) What is the value of ΔG° for this reaction at 600 K?

Correct Answer
verified

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?

Correct Answer
verified
B

Calculate the equilibrium constant at 25°C for the reaction of methane with water to form carbon dioxide and hydrogen. The data refer to 25°C. CH₄(g) + 2H₂O(g) ⇄ CO₂(g) + 4H₂(g)

Correct Answer
verified

Given: H₂O(l) → H₂O(s) ΔH° = −6.02 kJ at 273K Calculate the entropy change of the surroundings (ΔS_surr) when one mole of water freezes at 0°C and a pressure of one atmosphere.

Correct Answer
verified

As a chemical reaction proceeds toward equilibrium, the free energy of the system decreases.

Correct Answer
verified

Consider the following quantities used in thermodynamics: E, H, q, w, S, G. How many of them are state functions?

Correct Answer
verified

Correct Answer
verified
C

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

Correct Answer
verified

In which one of these pairs will the entropy of the first substance be greater than that of the second? Assume P and T are the same for each pair, unless stated otherwise.

Correct Answer
verified

Which of the following values is based on the Third Law of Thermodynamics?

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

You are given pure samples of ammonia, NH₃(g) , and nitrogen trifluoride, NF₃(g) . What prediction would you make concerning their standard molar entropies at 298 K?

Correct Answer
verified

Which one of the following phase changes decreases the entropy of the system?

Correct Answer
verified

The term microstate refers to the energy state of a single molecule in a system of many molecules.

Correct Answer
verified
False

A reaction has ΔG = 10.0 kJ and ΔG° = 15.0 kJ at a temperature of 50°C. Calculate the value of the reaction quotient under these conditions.

Correct Answer
verified

Which of the following should have the greatest molar entropy at 298 K?

Correct Answer
verified

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

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

Hydrogen sulfide decomposes according to the following reaction 2H2S(g) → 2H2(g) + S2(g) For this reaction at 298K ΔS° = 78.1 J/K, ΔH° = 169.4 kJ, and ΔG° = 146.1 kJ. What is the value of ΔG° at 900 K?

Correct AnswerverifiedShow Answer

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl3(g) + 1.5H2(g) → B(s) + 3HCl(g) Calculate ΔG° for the reaction.

Correct AnswerverifiedShow Answer

Sulfuryl dichloride is formed when sulfur dioxide reacts with chlorine. The data refer to 298 K. SO2(g) + Cl2(g) → SO2Cl2(g) What is the value of ΔG° for this reaction at 600 K?

Correct AnswerverifiedShow Answer

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?

Correct AnswerverifiedB

Calculate the equilibrium constant at 25°C for the reaction of methane with water to form carbon dioxide and hydrogen. The data refer to 25°C. CH4(g) + 2H2O(g) ⇄ CO2(g) + 4H2(g)

Correct AnswerverifiedShow Answer

Given: H2O(l) → H2O(s) ΔH° = −6.02 kJ at 273K Calculate the entropy change of the surroundings (ΔSsurr) when one mole of water freezes at 0°C and a pressure of one atmosphere.

Correct AnswerverifiedShow Answer

As a chemical reaction proceeds toward equilibrium, the free energy of the system decreases.

Correct AnswerverifiedShow Answer

Consider the following quantities used in thermodynamics: E, H, q, w, S, G. How many of them are state functions?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedC

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

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

Correct AnswerverifiedShow Answer

In which one of these pairs will the entropy of the first substance be greater than that of the second? Assume P and T are the same for each pair, unless stated otherwise.

Correct AnswerverifiedShow Answer

Which of the following values is based on the Third Law of Thermodynamics?

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

You are given pure samples of ammonia, NH3(g) , and nitrogen trifluoride, NF3(g) . What prediction would you make concerning their standard molar entropies at 298 K?

Correct AnswerverifiedShow Answer

Which one of the following phase changes decreases the entropy of the system?

Correct AnswerverifiedShow Answer

The term microstate refers to the energy state of a single molecule in a system of many molecules.

Correct AnswerverifiedFalse

A reaction has ΔG = 10.0 kJ and ΔG° = 15.0 kJ at a temperature of 50°C. Calculate the value of the reaction quotient under these conditions.

Correct AnswerverifiedShow Answer

Which of the following should have the greatest molar entropy at 298 K?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Hydrogen sulfide decomposes according to the following reaction 2H₂S(g) → 2H₂(g) + S₂(g) For this reaction at 298K ΔS° = 78.1 J/K, ΔH° = 169.4 kJ, and ΔG° = 146.1 kJ. What is the value of ΔG° at 900 K?

Correct Answer
verified

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl₃(g) + 1.5H₂(g) → B(s) + 3HCl(g) Calculate ΔG° for the reaction.

Correct Answer
verified

Sulfuryl dichloride is formed when sulfur dioxide reacts with chlorine. The data refer to 298 K. SO₂(g) + Cl₂(g) → SO₂Cl₂(g) What is the value of ΔG° for this reaction at 600 K?

Correct Answer
verified

Correct Answer
verified
B

Calculate the equilibrium constant at 25°C for the reaction of methane with water to form carbon dioxide and hydrogen. The data refer to 25°C. CH₄(g) + 2H₂O(g) ⇄ CO₂(g) + 4H₂(g)

Correct Answer
verified

Given: H₂O(l) → H₂O(s) ΔH° = −6.02 kJ at 273K Calculate the entropy change of the surroundings (ΔS_surr) when one mole of water freezes at 0°C and a pressure of one atmosphere.

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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C

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

Correct Answer
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Correct Answer
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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

You are given pure samples of ammonia, NH₃(g) , and nitrogen trifluoride, NF₃(g) . What prediction would you make concerning their standard molar entropies at 298 K?

Correct Answer
verified

Correct Answer
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Correct Answer
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False

Correct Answer
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Correct Answer
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