Question 1

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

Accepted Answer

A)   ( Δ\DeltaΔ S °\degree°   > 0,  Δ\DeltaΔ H °\degree°  > 0) 
B)   ( Δ\DeltaΔ S °\degree°   > 0,  Δ\DeltaΔ H °\degree°  
C)   ( Δ\DeltaΔ S °\degree°   Δ\DeltaΔ H °\degree°   
D)   ( Δ\DeltaΔ S °\degree°   Δ\DeltaΔ H °\degree°   > 0) 
E)   It is not possible for a reaction to be spontaneous at all temperatures.

Question 2

A certain process has  Δ\DeltaΔ 0H  °\degree° > 0,  Δ\DeltaΔ S  °\degree°  Δ\DeltaΔ G  °\degree° > 0. The values of  Δ\DeltaΔ H  °\degree°  and  Δ\DeltaΔ S  °\degree° 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 these conclusions is correct.

Question 3

Use the given data at 298 K to calculate  Δ\DeltaΔ G °\degree° for the reaction

Accepted Answer

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

Question 4

Elemental boron can be formed by reaction of boron trichloride with hydrogen. 3(g) ? A)  -18.2 J/K*mol B)  18.2 J/K*mol C)  290.1 J/K*mol D)  355.4 J/K*mol E)  450.6 J/K*mol " class="answers-bank-image d-inline" rel="preload" > 3(g) ? A)  -18.2 J/K*mol B)  18.2 J/K*mol C)  290.1 J/K*mol D)  355.4 J/K*mol E)  450.6 J/K*mol " class="answers-bank-image d-inline" rel="preload" > If  Δ\DeltaΔ S °\degree°   = 80.3 J/K for the reaction above, what is S  °\degree°  for BCl3(g) ?

Accepted Answer

A)   -18.2 J/K*mol
B)   18.2 J/K*mol
C)   290.1 J/K*mol
D)   355.4 J/K*mol
E)   450.6 J/K*mol

Question 5

(p. Various sections) 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 6

You are given pure samples of pentane,  CH3CH2CH2CH2CH3(l)  \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}(l)  CH3​CH2​CH2​CH2​CH3​(l)  , and 1,3-pentadiene,  CH2=CHCH=CHCH3(l)  \mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CHCH}_{3}(l)  CH2​=CHCH=CHCH3​(l)   What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

A)   S °\degree° pentane > S °\degree° 1,3-pentadiene
B)   S  °\degree° pentane °\degree° 1,3-pentadiene
C)   S °\degree° pentane  ≈\approx≈ S °\degree° 1,3-pentadiene
D)   S °\degree° pentane &#61501; S °\degree° 1,3-pentadiene + 2*pentane > S \degree 1,3-pentadiene 
B)   S  \degree pentane 1,3-pentadiene 
C)   S \degree pentane  \approx S \degree 1,3-pentadiene 
D)   S \degree pentane &#61501; S \degree 1,3-pentadiene + 2*  
E)   More information is needed to make reasonable predictions. " class="answers-bank-image d-inline" rel="preload" >
E)   More information is needed to make reasonable predictions.

Question 7

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

Accepted Answer

A)  (  Δ\DeltaΔ H °\degree°  > 0,  Δ\DeltaΔ S °\degree°  > 0) 
B)   ( Δ\DeltaΔ H °\degree°  > 0,  Δ\DeltaΔ S °\degree°  
C)   ( Δ\DeltaΔ H °\degree° Δ\DeltaΔ S °\degree° > 0) 
D)   ( Δ\DeltaΔ H °\degree°  Δ\DeltaΔ S °\degree°  
E)   None of these choices is correct.

Question 8

Elemental boron can be formed by reaction of boron trichloride with hydrogen.  Calculate  Δ\DeltaΔ G °\degree°  for the reaction.

Accepted Answer

A)   -293.4 kJ
B)   293.4 kJ
C)   -102.8 kJ
D)   102.8 kJ
E)   None of these choices is correct.

Question 9

Which relationship or statement best describes  Δ\DeltaΔ S  °\degree°  for the following reaction? 2NH3(g)  + 2ClF3(g)   →\rightarrow→  6HF(g)  + N2(g)  + Cl2(g)

Accepted Answer

A)   ( Δ\DeltaΔ SF  °\degree°≈\approx≈  0) 
B)   ( Δ\DeltaΔ S  °\degree°  
C)   ( Δ\DeltaΔ S  °\degree° > 0) 
D)   ( Δ\DeltaΔ S  °\degree°  =  Δ\DeltaΔ H  °\degree° /T) 
E)   More information is needed to make a reasonable prediction.

Question 10

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

Accepted Answer

T = 463 K. The calculation is ...

Question 11

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 people

Question 12

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

Accepted Answer

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

Question 13

In the expression, S = k ln W, W is called the number of microstates. Explain clearly the meaning of the word "microstate," and why a system under a given set of conditions normally has many microstates.

Accepted Answer

A microstate is a specific, quantized st...

Question 14

Which relationship or statement best describes  Δ\DeltaΔ S °\degree°  for the following reaction?  0)  D)  ( \Delta S \degree  =  \Delta H \degree /T)  E)  More information is needed to make a reasonable prediction. " class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   ( Δ\DeltaΔ S °\degree°   ≈\approx≈  0) 
B)   ( Δ\DeltaΔ S °\degree° 
C)   ( Δ\DeltaΔ S °\degree°  > 0) 
D)   ( Δ\DeltaΔ S °\degree°  =  Δ\DeltaΔ H °\degree° /T) 
E)   More information is needed to make a reasonable prediction.

Question 15

Which of the following conditions will ensure that a chemical reaction will definitely proceed in the forward direction, toward products?

Accepted Answer

A)   ( Δ\DeltaΔ H > 0) 
B)   ( Δ\DeltaΔ H 
C)   ( Δ\DeltaΔ Ssys > 0) 
D)   ( Δ\DeltaΔ Ssurr >  Δ\DeltaΔ Ssys) 
E)   ( Δ\DeltaΔ S >  Δ\DeltaΔ H/T)

Question 16

"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 298 K and determine whether or not a diamond is "forever." C(diamond)   °\degree° C(graphite) 
Data:  Δ\DeltaΔ Hf °\degree° (diamond)  = 1.895 kJ/mol; S °\degree° (diamond)  = 2.337 J mol¯1 K¯1; S °\degree° (graphite)  = 5.740 J mol¯1K¯1.

Accepted Answer

A)   ( Δ\DeltaΔ G °\degree°  = 2.19 kJ; forever
B)   ( Δ\DeltaΔ G °\degree° = -1.90 kJ; not forever) 
C)   ( Δ\DeltaΔ G °\degree°  = -2.90 kJ; not forever) 
D)  (  Δ\DeltaΔ G °\degree°  = 1.90 kJ; forever) 
E)   ( Δ\DeltaΔ G °\degree°  = < -1000 kJ; not forever)

Question 17

State the second and third laws of thermodynamics.

Accepted Answer

All spontaneous processes are ...

Question 18

Which of the following is true for a system at equilibrium?

Accepted Answer

A)   ( Δ\DeltaΔ S °\degree° sys =  Δ\DeltaΔ S °\degree° surr) 
B)   ( Δ\DeltaΔ S °\degree° sys = - Δ\DeltaΔ S °\degree° surr) 
C)   ( Δ\DeltaΔ S °\degree° sys =  Δ\DeltaΔ S °\degree° surr = 0
D)   ( Δ\DeltaΔ S °\degree° univ > 0) 
E)   None of these choices is a sufficient condition.

Question 19

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)   sublimation

Question 20

Which relationship or statement best describes  Δ\DeltaΔ S °\degree°  for the following reaction? HgS(s)  + O2(g)   →\rightarrow→  Hg(l)  + SO2(g)

Accepted Answer

A)  (  Δ\DeltaΔ S °\degree°≈\approx≈  0) 
B)   ( Δ\DeltaΔ S °\degree°  
C)   ( Δ\DeltaΔ S °\degree°  > 0) 
D)   ( Δ\DeltaΔ S °\degree° =  Δ\DeltaΔ H °\degree° /T) 
E)   More information is needed to make a reasonable prediction.

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

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

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

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

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

Correct Answer
verified

In the expression, S = k ln W, W is called the number of microstates. Explain clearly the meaning of the word "microstate," and why a system under a given set of conditions normally has many microstates.

Correct Answer
verified
A microstate is a specific, quantized st...
View Answer

Correct Answer
verified

You are given pure samples of pentane, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}(l)$ , and 1,3-pentadiene, $\mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CHCH}_{3}(l)$ What prediction would you make concerning their standard molar entropies at 298 K?

Correct Answer
verified

State the second and third laws of thermodynamics.

Correct Answer
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All spontaneous processes are ...
View Answer

Which relationship or statement best describes $\Delta$ S $\degree$ for the following reaction? 2NH₃(g) + 2ClF₃(g) $\rightarrow$ 6HF(g) + N₂(g) + Cl₂(g)

Correct Answer
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Correct Answer
verified

Which of the following conditions will ensure that a chemical reaction will definitely proceed in the forward direction, toward products?

Correct Answer
verified

Correct Answer
verified

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

Correct Answer
verified

Which relationship or statement best describes $\Delta$ S $\degree$ for the following reaction? HgS(s) + O₂(g) $\rightarrow$ Hg(l) + SO₂(g)

Correct Answer
verified

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

Correct Answer
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Which of the following is true for a system at equilibrium?

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

Correct Answer
verified

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

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

Elemental boron can be formed by reaction of boron trichloride with hydrogen. If Δ\DeltaΔ S °\degree° = 80.3 J/K for the reaction above, what is S °\degree° for BCl3(g) ?

Correct AnswerverifiedShow Answer

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

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

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

(p. Various sections) For a given reaction, a change in the pressure may result in a change in the sign of Δ\DeltaΔ G.

Correct AnswerverifiedShow Answer

In the expression, S = k ln W, W is called the number of microstates. Explain clearly the meaning of the word "microstate," and why a system under a given set of conditions normally has many microstates.

Correct AnswerverifiedA microstate is a specific, quantized st...View AnswerShow Answer

Elemental boron can be formed by reaction of boron trichloride with hydrogen. Calculate Δ\DeltaΔ G °\degree° for the reaction.

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

State the second and third laws of thermodynamics.

Correct AnswerverifiedAll spontaneous processes are ...View AnswerShow Answer

Which relationship or statement best describes Δ\DeltaΔ S °\degree° for the following reaction? 2NH3(g) + 2ClF3(g) →\rightarrow→ 6HF(g) + N2(g) + Cl2(g)

Correct AnswerverifiedShow Answer

Which relationship or statement best describes Δ\DeltaΔ S °\degree° for the following reaction?

Correct AnswerverifiedShow Answer

Which of the following conditions will ensure that a chemical reaction will definitely proceed in the forward direction, toward products?

Correct AnswerverifiedShow Answer

Use the given data at 298 K to calculate Δ\DeltaΔ G °\degree° for the reaction

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which relationship or statement best describes Δ\DeltaΔ S °\degree° for the following reaction? HgS(s) + O2(g) →\rightarrow→ Hg(l) + SO2(g)

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following is true for a system at equilibrium?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

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

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

Correct Answer
verified

Correct Answer
verified

(p. Various sections) 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
A microstate is a specific, quantized st...
View Answer

Correct Answer
verified

Correct Answer
verified

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

Which relationship or statement best describes $\Delta$ S $\degree$ for the following reaction? 2NH₃(g) + 2ClF₃(g) $\rightarrow$ 6HF(g) + N₂(g) + Cl₂(g)

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Which relationship or statement best describes $\Delta$ S $\degree$ for the following reaction? HgS(s) + O₂(g) $\rightarrow$ Hg(l) + SO₂(g)

Correct Answer
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A certain process has $\Delta$ 0H $\degree$ > 0, $\Delta$ S $\degree$ < 0, and $\Delta$ G $\degree$ > 0. The values of $\Delta$ H $\degree$ and $\Delta$ S $\degree$ do not depend on the temperature. Which of the following is a correct conclusion about this process?

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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