Question 1

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

Accepted Answer

A)  ( Δ\DeltaΔ H° f = 0 for Al(s) at 298 K) 
B)  ( Δ\DeltaΔ G° f = 0 for H2(g) at 298 K) 
C)  S° = 51.446 J/(mol·K) for Na(s) at 298 K
D)  q sys 2O(l)   →	o→  H2O(s) at 0°C
E)  None of these choices is correct. F) A) and E)
G) None of the above

Question 2

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 wil...

Question 3

When a sky diver free-falls through the air,the process is

Accepted Answer

A)  non-spontaneous because he is accelerating due to the force applied by gravity.
B)  non-spontaneous because he is losing potential energy.
C)  non-spontaneous because he had planned the jump for two weeks.
D)  spontaneous.
E)  in equilibrium.F) A) and B)
G) A) and C)

Question 4

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  ≈\approx≈  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) B) and E)
G) B) and C)

Question 5

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

Accepted Answer

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

Question 6

For the reaction of xenon and fluorine gases to form solid XeF4,$\Delta$H° = -251 kJ and $\Delta$G° = -121 kJ at 25°C.Calculate $\Delta$S° for the reaction.

Accepted Answer

The answer of For the reaction of xenon and fluorine...

Question 7

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

Accepted Answer

A)  ( Δ\DeltaΔ S°·> 0, Δ\DeltaΔ H° > 0) 
B)  ( Δ\DeltaΔ S° > 0, Δ\DeltaΔ H° 
C)  ( Δ\DeltaΔ S° Δ\DeltaΔ H° 
D)  ( Δ\DeltaΔ S° Δ\DeltaΔ H° > 0) 
E)  ( Δ\DeltaΔ G° > 0)  F) A) and C)
G) C) and D)

Question 8

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

Accepted Answer

T = 463 K.The calculation is b...

Question 9

Hydrogen sulfide decomposes according to the following reaction
2H2S(g)   →	o→ 2H2(g) + S2(g) 
For this reaction at 298K  Δ\DeltaΔ S° = 78.1 J/K, Δ\DeltaΔ H° = 169.4 kJ,and  Δ\DeltaΔ G° = 146.1 kJ.What is the value of  Δ\DeltaΔ G° at 900 K?

Accepted Answer

A)  -69,881 kJ
B)  48.4 kJ
C)  99.1 kJ
D)  240 kJ
E)  441 kJ F) C) and E)
G) None of the above

Question 10

Which of the following results in a decrease in the entropy of the system?

Accepted Answer

A)  O2(g) ,300 K  →	o→  O2(g) ,400 K
B)  H2O(s) ,0°C  →	o→   H2O(l) ,0°C
C)  N2(g) ,25°C  →	o→   N2(aq) ,25°C
D)  NH3(l) ,-34.5°C  →	o→   NH3(g) ,-34.5°C
E)  2H2O2(g)   →	o→   2H2O(g) + O2(g)  F) D) and E)
G) A) and E)

Question 11

Consider the figure below which shows  Δ\DeltaΔ G° for a chemical process plotted against absolute temperature.From this plot,it is reasonable to conclude that:  0, \Delta S° > 0)  B) ( \Delta H° > 0, \Delta S°  0)  D) ( \Delta H°

Accepted Answer

A)  ( Δ\DeltaΔ H° > 0, Δ\DeltaΔ S° > 0) 
B)  ( Δ\DeltaΔ H° > 0, Δ\DeltaΔ S° 
C)  9 Δ\DeltaΔ H° Δ\DeltaΔ S° > 0) 
D)  ( Δ\DeltaΔ H° Δ\DeltaΔ S° 
E)  None of these choices is correct. F) None of the above
G) C) and D)

Question 12

For a given reaction,a change in the pressure may result in a change in the sign of $\Delta$G.

Accepted Answer

A) True 
 B)False

Question 13

Nitric oxide reacts with chlorine to form NOCl.The data refer to 298 K.
2NO(g) + Cl2(g)   →	o→  2NOCl(g) 
2(g)   	o  2NOCl(g)    What is the value of  \Delta G° for this reaction at 550 K? A) -143.76 kJ B) -78.78 kJ C) -22.24 kJ D) -10.56 kJ E) 66,600 kJ " class="answers-bank-image d-inline" rel="preload" >
What is the value of  Δ\DeltaΔ G° for this reaction at 550 K?

Accepted Answer

A)  -143.76 kJ
B)  -78.78 kJ
C)  -22.24 kJ
D)  -10.56 kJ
E)  66,600 kJ F) A) and B)
G) A) and C)

Question 14

State the second and third laws of thermodynamics.

Accepted Answer

All spontaneous processes are ...

Question 15

For what signs of $\Delta$H and $\Delta$S will a process
a.be spontaneous at high temperatures but not at low temperatures?
b.not be spontaneous at any temperatures?

Accepted Answer

a.

H > 0,

S ...

Question 16

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

Accepted Answer

A) True 
 B)False

Question 17

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid.
H3PO4(s)  3PO4(s)    H3PO4(l)  Use the following thermodynamic data at 298 K to determine this temperature.   A) 286 K B) 305 K C) 315 K D) 347 K E) 3170 K" class="answers-bank-image d-inline" rel="preload" >
H3PO4(l) 
Use the following thermodynamic data at 298 K to determine this temperature.
3PO4(s)    H3PO4(l)  Use the following thermodynamic data at 298 K to determine this temperature.   A) 286 K B) 305 K C) 315 K D) 347 K E) 3170 K" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  286 K
B)  305 K
C)  315 K
D)  347 K
E)  3170 KF) All of the above
G) C) and E)

Question 18

Calculate  Δ\DeltaΔ G° for the combustion of propane.
C3H8(g) + 5O2(g)   →	o→ 3CO2(g) + 4H2O(g) 
3H8(g) + 5O2(g)   	o 3CO2(g) + 4H2O(g)    A) -2073.1 kJ B) -1387.3 kJ C) -598.5 kJ D) 598.5 kJ E) 2073.1 kJ " class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  -2073.1 kJ
B)  -1387.3 kJ
C)  -598.5 kJ
D)  598.5 kJ
E)  2073.1 kJ F) A) and B)
G) C) and D)

Question 19

Use the given data at 298 K to calculate  Δ\DeltaΔ G° for the reaction
2Cl2(g) + SO2(g)   →	o→  SOCl2(g) + Cl2O(g) 
2(g) + SO2(g)   	o  SOCl2(g) + Cl2O(g)    A) 129.3 kJ B) 133.6 kJ C) 196.0 kJ D) 199.8 kJ E) 229.6 kJ " class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  129.3 kJ
B)  133.6 kJ
C)  196.0 kJ
D)  199.8 kJ
E)  229.6 kJ F) B) and D)
G) C) and E)

Question 20

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

Accepted Answer

A)  ( Δ\DeltaΔ S° > 0, Δ\DeltaΔ H° > 0) 
B)  ( Δ\DeltaΔ S° > 0, Δ\DeltaΔ H° 
C)  ( Δ\DeltaΔ S° Δ\DeltaΔ H° 
D)  ( Δ\DeltaΔ S° Δ\DeltaΔ H° > 0) 
E)  ( Δ\DeltaΔ G° > 0)  F) B) and E)
G) B) and D)

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

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 wil...
View 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 Answer
verified

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

Correct Answer
verified

Correct Answer
verified

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

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

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

Correct Answer
verified

Hydrogen sulfide decomposes according to the following reaction 2H₂S(g) $\to$ 2H₂(g) + S₂(g) For this reaction at 298K $\Delta$ S° = 78.1 J/K, $\Delta$ H° = 169.4 kJ,and $\Delta$ G° = 146.1 kJ.What is the value of $\Delta$ G° at 900 K?

Correct Answer
verified

Correct Answer
verified

State the second and third laws of thermodynamics.

Correct Answer
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All spontaneous processes are ...
View Answer

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

Correct Answer
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For what signs of $\Delta$ H and $\Delta$ S will a process a.be spontaneous at high temperatures but not at low temperatures? b.not be spontaneous at any temperatures?

Correct Answer
verified
a.H > 0,S ...
View Answer

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

Correct Answer
verified

For the reaction of xenon and fluorine gases to form solid XeF₄, $\Delta$ H° = -251 kJ and $\Delta$ G° = -121 kJ at 25°C.Calculate $\Delta$ S° for the reaction.

Correct Answer
verified

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

Correct Answer
verified

Which of the following results in a decrease in the entropy of the system?

Correct Answer
verified

Correct Answer
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For a given reaction,a change in the pressure may result in a change in the sign of $\Delta$ G.

Correct Answer
verified

Correct Answer
verified

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H₃PO₄(s) H₃PO₄(l) Use the following thermodynamic data at 298 K to determine this temperature.

Correct Answer
verified

When a sky diver free-falls through the air,the process is

Correct Answer
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Exam 20: Thermodynamics: Entropy, free Energy, and the Direction of Chemical Reactions

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 wil...View AnswerShow 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

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

Correct AnswerverifiedShow Answer

Calculate Δ\DeltaΔ G° for the combustion of propane. C3H8(g) + 5O2(g) →\to→ 3CO2(g) + 4H2O(g)

Correct AnswerverifiedShow Answer

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

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

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Nitric oxide reacts with chlorine to form NOCl.The data refer to 298 K. 2NO(g) + Cl2(g) →\to→ 2NOCl(g) What is the value of Δ\DeltaΔ G° for this reaction at 550 K?

Correct AnswerverifiedShow Answer

State the second and third laws of thermodynamics.

Correct AnswerverifiedAll spontaneous processes are ...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

For what signs of Δ\DeltaΔ H and Δ\DeltaΔ S will a process a.be spontaneous at high temperatures but not at low temperatures? b.not be spontaneous at any temperatures?

Correct Answerverifieda.H > 0,S ...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

For the reaction of xenon and fluorine gases to form solid XeF4, Δ\DeltaΔ H° = -251 kJ and Δ\DeltaΔ G° = -121 kJ at 25°C.Calculate Δ\DeltaΔ S° for the reaction.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following results in a decrease in the entropy of the system?

Correct AnswerverifiedShow Answer

Consider the figure below which shows Δ\DeltaΔ G° for a chemical process plotted against absolute temperature.From this plot,it is reasonable to conclude that:

Correct AnswerverifiedShow Answer

For a given reaction,a change in the pressure may result in a change in the sign of Δ\DeltaΔ G.

Correct AnswerverifiedShow Answer

Use the given data at 298 K to calculate Δ\DeltaΔ G° for the reaction 2Cl2(g) + SO2(g) →\to→ SOCl2(g) + Cl2O(g)

Correct AnswerverifiedShow Answer

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H3PO4(s) H3PO4(l) Use the following thermodynamic data at 298 K to determine this temperature.

Correct AnswerverifiedShow Answer

When a sky diver free-falls through the air,the process is

Correct AnswerverifiedShow Answer

Correct Answer
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a.A spontaneous process is one which wil...
View 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 Answer
verified

Correct Answer
verified

Correct Answer
verified

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

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

Correct Answer
verified

Hydrogen sulfide decomposes according to the following reaction 2H₂S(g) $\to$ 2H₂(g) + S₂(g) For this reaction at 298K $\Delta$ S° = 78.1 J/K, $\Delta$ H° = 169.4 kJ,and $\Delta$ G° = 146.1 kJ.What is the value of $\Delta$ G° at 900 K?

Correct Answer
verified

Correct Answer
verified

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

Correct Answer
verified

For what signs of $\Delta$ H and $\Delta$ S will a process a.be spontaneous at high temperatures but not at low temperatures? b.not be spontaneous at any temperatures?

Correct Answer
verified
a.H > 0,S ...
View Answer

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

Correct Answer
verified

For the reaction of xenon and fluorine gases to form solid XeF₄, $\Delta$ H° = -251 kJ and $\Delta$ G° = -121 kJ at 25°C.Calculate $\Delta$ S° for the reaction.

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

For a given reaction,a change in the pressure may result in a change in the sign of $\Delta$ G.

Correct Answer
verified

Correct Answer
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The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H₃PO₄(s) H₃PO₄(l) Use the following thermodynamic data at 298 K to determine this temperature.

Correct Answer
verified

Correct Answer
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