Question 1

A chemical reaction has F1F1F1S1F1F1F10H° = 42.8 kJ and F1F1F1S1F1F1F10S° = 92.5 J/K, at 25°C. Calculate the temperature at which F1F1F1S1F1F1F10G° = 0. State any approximation involved in your calculation.

Accepted Answer

T = 463 K. The calculation is ...

Question 2

Consider the figure which shows G° for a chemical process plotted against absolute temperature. G° for a chemical process plotted against absolute temperature.   Which one of the following is an incorrect conclusion, based on the information in the diagram? A)  .H° > 0 B)  .S° > 0 C)  The reaction is spontaneous at high temperatures. D)  .S° increases with temperature while H° remains constant. E)  There exists a certain temperature at which H° = TS°." class="answers-bank-image d-inline" rel="preload" > Which one of the following is an incorrect conclusion, based on the information in the diagram?

Accepted Answer

A)   .H° > 0
B)   .S° > 0
C)   The reaction is spontaneous at high temperatures.
D)   .S° increases with temperature while H° remains constant.
E)   There exists a certain temperature at which H° = TS°.F) A) and C)
G) A) and B)

Question 3

Given: H2O(l)   H2O(g)  H° = 40.7 kJ at 373K What is the entropy change in the system (S)  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) B) and D)
G) C) and D) C

Question 4

Calculate S° for the reaction S° for the reaction   A)  -254.96 J/K B)  -198.02 J/K C)  198.02 J/K D)  254.96 J/K E)  471.86 J/K" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   -254.96 J/K
B)   -198.02 J/K
C)   198.02 J/K
D)   254.96 J/K
E)   471.86 J/KF) A) and C)
G) A) and E)

Question 5

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

Accepted Answer

A)   .S° > 0, H° > 0
B)   .S° > 0, H° 
C)   .S° H° 
D)   .S° H° > 0
E)   .G° > 0F) A) and E)
G) None of the above

Question 6

Which relationship best describes S° for the following reaction? 
CO(g)  + H2O(g)   CO2(g)  + H2(g)

Accepted Answer

A)   .S° = H°
B)   .S° = H°/T
C)   .S° > 0
D)   .S° 
E)   .S°   0F) A) and B)
G) B) and D)

Question 7

Which one of the following changes of state increases the entropy of the system?

Accepted Answer

A)   condensation
B)   cooling a gas
C)   freezing
D)   crystallization
E)   sublimationF) C) and D)
G) B) and E)

Question 8

For each of the following pairs, predict which (A or B) will have the greater entropy, and in one sentence indicate your reasoning.

Accepted Answer

a. A has greater entropy. HI and HBr are...

Question 9

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

Accepted Answer

A)   .S° > 0, H° > 0
B)   .S° > 0, H° 
C)   .S° H° 
D)   .S° H° > 0
E)   .G° > 0F) All of the above
G) B) and E)

Question 10

Elemental boron can be formed by reaction of boron trichloride with hydrogen.

Accepted Answer

A)   -293.4 kJ
B)   293.4 kJ
C)   -102.8 kJ
D)   102.8 kJ
E)   none of the aboveF) A) and E)
G) A) and D) D

Question 11

Calculate S° for the reaction S° for the reaction   A)  -118.2 J/K B)  -104.8 J/K C)  104.8 J/K D)  118.2 J/K E)  1270.0 J/K" class="answers-bank-image d-inline" rel="preload" >

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) None of the above
G) B) and D)

Question 12

a. Explain what is meant by a spontaneous process.
b. Is a spontaneous process necessarily a rapid one? Explain, and provide a real reaction as an example to illustrate your answer.

Accepted Answer

a. A spontaneous process is one which will occur naturally, given enough time.
b. No, a spontaneous process may be immeasurably slow. An example is the conversion of diamond to graphite at room temperature and one atmosphere.

Question 13

The formation constant for the reaction 
f  = 1.7 × 107 at 25°C. What is G° 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" >
Is Kf  = 1.7 × 107 at 25°C. What is G° at this temperature?

Accepted Answer

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

Question 14

A certain process has H° > 0, S° G° > 0. The values of H° and S° do not depend on the temperature. Which of the following is a correct conclusion about this process?

Accepted Answer

A)   It is non-spontaneous at all T.
B)   It is spontaneous at high T.
C)   It is spontaneous at low T.
D)   It is spontaneous at all T.
E)   None of the above conclusions is correct.F) B) and E)
G) A) and B)

Question 15

Iron(III)  oxide can be reduced by carbon monoxide. -6 B)  1.3 × 10-3 C)  2.2 × 104 D)  1.4 × 105 E)  > 2.0 × 105" class="answers-bank-image d-inline" rel="preload" >
Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature. -6 B)  1.3 × 10-3 C)  2.2 × 104 D)  1.4 × 105 E)  > 2.0 × 105" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   7.0 × 10-6
B)   1.3 × 10-3
C)   2.2 × 104
D)   1.4 × 105
E)   > 2.0 × 105F) All of the above
G) A) and B)

Question 16

Compare one mole of ice with one mole of liquid water, both at 1.0 atm and 0°C. The melting point of ice at 1.0 atm is 0°C. For the process
H2O(s) F1F1F1S1F1F1F10 H2O(l)
under these conditions predict whether each of the following quantities will be greater than, less than, or equal to, zero . Explain each prediction in one sentence.
a. F1F1F1S1F1F1F10H° b. F1F1F1S1F1F1F10S° c. F1F1F1S1F1F1F10G°

Accepted Answer

a. H° > 0. The solid-to-...

Question 17

Calculate G° for the reaction of ammonia with fluorine. G° for the reaction of ammonia with fluorine.   A)  179.1 kJ B)  -179.1 kJ C)  1539.7 kJ D)  -1539.7 kJ E)  none of the above" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   179.1 kJ
B)   -179.1 kJ
C)   1539.7 kJ
D)   -1539.7 kJ
E)   none of the aboveF) A) and C)
G) A) and B)

Question 18

State the second and third laws of thermodynamics.

Accepted Answer

All spontaneous processes are ...

Question 19

You are given pure samples of ethane, C2H6(g) , and toluene, C7H8(l) . What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

A)   S°ethane > S°toluene
B)   S°ethane toluene
C)   S°ethane  (S°toluene)  ÷ 3
D)   S°ethane  S°toluene
E)   Since toluene is much more complex than ethane, but ethane is in the gas phase while toluene is a liquid, none of the above predictions can be confidently made without further information or calculations.F) C) and D)
G) D) and E)

Question 20

For a given reaction, a change in the pressure may result in a change in the sign of F1F1F1S1F1F1F10G.

Accepted Answer

A) True 
 B)False

Exam 20: Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

A chemical reaction has H° = 42.8 kJ and S° = 92.5 J/K, at 25°C. Calculate the temperature at which G° = 0. State any approximation involved in your calculation.

Correct Answer
verified
T = 463 K. The calculation is ...
View Answer

Consider the figure which shows G° for a chemical process plotted against absolute temperature. Which one of the following is an incorrect conclusion, based on the information in the diagram?

Correct Answer
verified

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

Correct Answer
verified
C

Calculate S° for the reaction

Correct Answer
verified

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

Correct Answer
verified

Which relationship best describes S° for the following reaction? CO(g) + H₂O(g)  CO₂(g) + H₂(g)

Correct Answer
verified

Which one of the following changes of state increases the entropy of the system?

Correct Answer
verified

For each of the following pairs, predict which (A or B) will have the greater entropy, and in one sentence indicate your reasoning.

Correct Answer
verified
a. A has greater entropy. HI and HBr are...
View Answer

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

Correct Answer
verified

Elemental boron can be formed by reaction of boron trichloride with hydrogen.

Correct Answer
verified
D

Calculate S° for the reaction

Correct Answer
verified

a. Explain what is meant by a spontaneous process. b. Is a spontaneous process necessarily a rapid one? Explain, and provide a real reaction as an example to illustrate your answer.

Correct Answer
verified
a. A spontaneous process is one which will occur naturally, given enough time. b. No, a spontaneous process may be immeasurably slow. An example is the conversion of diamond to graphite at room temperature and one atmosphere.

The formation constant for the reaction Is K_f = 1.7 × 10⁷ at 25°C. What is G°at this temperature?

Correct Answer
verified

A certain process has H° > 0, S° < 0, and G° > 0. The values of H° and S° do not depend on the temperature. Which of the following is a correct conclusion about this process?

Correct Answer
verified

Iron(III) oxide can be reduced by carbon monoxide. Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature.

Correct Answer
verified

Correct Answer
verified
a. H° > 0. The solid-to-...
View Answer

Calculate G°for the reaction of ammonia with fluorine.

Correct Answer
verified

State the second and third laws of thermodynamics.

Correct Answer
verified
All spontaneous processes are ...
View Answer

You are given pure samples of ethane, C₂H₆(g) , and toluene, C₇H₈(l) . What prediction would you make concerning their standard molar entropies at 298 K?

Correct Answer
verified

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

Correct Answer
verified

Exam 20: Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

A chemical reaction has H° = 42.8 kJ and S° = 92.5 J/K, at 25°C. Calculate the temperature at which G° = 0. State any approximation involved in your calculation.

Correct AnswerverifiedT = 463 K. The calculation is ...View AnswerShow Answer

Consider the figure which shows G° for a chemical process plotted against absolute temperature. Which one of the following is an incorrect conclusion, based on the information in the diagram?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedC

Calculate S° for the reaction

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which relationship best describes S° for the following reaction? CO(g) + H2O(g)  CO2(g) + H2(g)

Correct AnswerverifiedShow Answer

Which one of the following changes of state increases the entropy of the system?

Correct AnswerverifiedShow Answer

For each of the following pairs, predict which (A or B) will have the greater entropy, and in one sentence indicate your reasoning.

Correct Answerverifieda. A has greater entropy. HI and HBr are...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

Elemental boron can be formed by reaction of boron trichloride with hydrogen.

Correct AnswerverifiedD

Calculate S° for the reaction

Correct AnswerverifiedShow Answer

a. Explain what is meant by a spontaneous process. b. Is a spontaneous process necessarily a rapid one? Explain, and provide a real reaction as an example to illustrate your answer.

Correct Answerverifieda. A spontaneous process is one which will occur naturally, given enough time. b. No, a spontaneous process may be immeasurably slow. An example is the conversion of diamond to graphite at room temperature and one atmosphere.

The formation constant for the reaction Is Kf = 1.7 × 107 at 25°C. What is G° at this temperature?

Correct AnswerverifiedShow Answer

A certain process has H° > 0, S° < 0, and G° > 0. The values of H° and S° do not depend on the temperature. Which of the following is a correct conclusion about this process?

Correct AnswerverifiedShow Answer

Iron(III) oxide can be reduced by carbon monoxide. Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature.

Correct AnswerverifiedShow Answer

Correct Answerverifieda. H° > 0. The solid-to-...View AnswerShow Answer

Calculate G° for the reaction of ammonia with fluorine.

Correct AnswerverifiedShow Answer

State the second and third laws of thermodynamics.

Correct AnswerverifiedAll spontaneous processes are ...View AnswerShow Answer

You are given pure samples of ethane, C2H6(g) , and toluene, C7H8(l) . What prediction would you make concerning their standard molar entropies at 298 K?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Correct Answer
verified
T = 463 K. The calculation is ...
View Answer

Correct Answer
verified

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

Correct Answer
verified
C

Correct Answer
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Correct Answer
verified

Which relationship best describes S° for the following reaction? CO(g) + H₂O(g)  CO₂(g) + H₂(g)

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
a. A has greater entropy. HI and HBr are...
View Answer

Correct Answer
verified

Correct Answer
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D

Correct Answer
verified

Correct Answer
verified
a. A spontaneous process is one which will occur naturally, given enough time. b. No, a spontaneous process may be immeasurably slow. An example is the conversion of diamond to graphite at room temperature and one atmosphere.

The formation constant for the reaction Is K_f = 1.7 × 10⁷ at 25°C. What is G°at this temperature?

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
a. H° > 0. The solid-to-...
View Answer

Calculate G°for the reaction of ammonia with fluorine.

Correct Answer
verified

Correct Answer
verified
All spontaneous processes are ...
View Answer

You are given pure samples of ethane, C₂H₆(g) , and toluene, C₇H₈(l) . What prediction would you make concerning their standard molar entropies at 298 K?

Correct Answer
verified

Correct Answer
verified