Question 1

Why can endothermic reactions be spontaneous?

Accepted Answer

Even though an endothermic process requi

Question 2

Consider the following reaction at constant pressure. Use the information here to determine the value of ΔSsurr at 398 K. Predict whether or not this reaction will be spontaneous at this temperature. 4NH3(g) + 3O2(g) → 2N2(g) + 6H2O(g) ΔrH = -1267 kJ

Accepted Answer

A)  ΔSsurr = +12.67 kJ K-1 mol-1, reaction is not spontaneous 
B)  ΔSsurr = -12.67 kJ K-1 mol-1, reaction is spontaneous 
C)  ΔSsurr = +50.4 kJ K-1 mol-1, reaction is not spontaneous 
D)  ΔSsurr = +3.18 kJ K-1 mol-1, reaction is spontaneous 
E)  ΔSsurr = -3.18 kJ K-1 mol-1, reaction is not spontaneous 
A)  ΔSsurr = +12.67 kJ K-1 mol-1, reaction is not spontaneous 
B)  ΔSsurr = -12.67 kJ K-1 mol-1, reaction is spontaneous 
C)  ΔSsurr = +50.4 kJ K-1 mol-1, reaction is not spontaneous 
D)  ΔSsurr = +3.18 kJ K-1 mol-1, reaction is spontaneous 
E)  ΔSsurr = -3.18 kJ K-1 mol-1, reaction is not spontaneous

Question 3

Which of the following statements is TRUE?

Accepted Answer

A)  A spontaneous reaction is a reaction that takes place without any outside intervention. 
B)  Thermodynamics is a study of reaction rates. 
C)  A nonspontaneous reaction is a reaction that does not take place under any conditions. 
D)  Chemical kinetics is a discipline that studies the spontaneity of chemical reactions. 
E)  Every spontaneous reaction is a very rapid reaction. 
A)  A spontaneous reaction is a reaction that takes place without any outside intervention. 
B)  Thermodynamics is a study of reaction rates. 
C)  A nonspontaneous reaction is a reaction that does not take place under any conditions. 
D)  Chemical kinetics is a discipline that studies the spontaneity of chemical reactions. 
E)  Every spontaneous reaction is a very rapid reaction.

Question 4

Choose the statement below that is TRUE.

Accepted Answer

A)  If K > 1, ΔrG for forward reaction is positive. 
B)  If K rG for forward reaction is negative. 
C)  If K > 1, ΔrG for reverse reaction is negative. 
D)  ΔrG = 0 at equilibrium. 
E)  If K rG for reverse reaction is positive. 
A)  If K > 1, ΔrG for forward reaction is positive. 
B)  If K rG for forward reaction is negative. 
C)  If K > 1, ΔrG for reverse reaction is negative. 
D)  ΔrG = 0 at equilibrium. 
E)  If K rG for reverse reaction is positive.

Question 5

Consider a reaction that has a negative ΔrH and a positive ΔrS. Which of the following statements is TRUE?

Accepted Answer

A)  This reaction will be spontaneous only at high temperatures. 
B)  This reaction will be spontaneous at all temperatures. 
C)  This reaction will be nonspontaneous at all temperatures. 
D)  This reaction will be nonspontaneous only at high temperatures. 
E)  This reaction will be spontaneous only at absolute zero (0 Kelvin). 
A)  This reaction will be spontaneous only at high temperatures. 
B)  This reaction will be spontaneous at all temperatures. 
C)  This reaction will be nonspontaneous at all temperatures. 
D)  This reaction will be nonspontaneous only at high temperatures. 
E)  This reaction will be spontaneous only at absolute zero (0 Kelvin).

Question 6

Calculate ΔrG at 298 K under the conditions shown below for the following reaction: 3O2(g) → 2O3(g) ΔrG° = +326 kJ
P(O2) = 0.41 atm, P(O3) = 5.2 atm

Accepted Answer

A)  +341 kJ 
B)  +17.8 kJ 
C)  +332 kJ 
D)  -47.4 kJ 
E)  -109 kJ 
A)  +341 kJ 
B)  +17.8 kJ 
C)  +332 kJ 
D)  -47.4 kJ 
E)  -109 kJ

Question 7

Calculate ΔρS° for the following reaction. The S° for each species is shown below the reaction. P4(g) + 10Cl2(g) → 4PCl5(g)
S°(J K-1 mol-1) 280.0 223.1 364.6

Accepted Answer

A)  -138.5 J K-1 mol-1 
B)  -1052.6 J K-1 mol-1 
C)  +171.3 J K-1 mol-1 
D)  -583.6 J K-1 mol-1 
E)  +2334.6 J K-1 mol-1 
A)  -138.5 J K-1 mol-1 
B)  -1052.6 J K-1 mol-1 
C)  +171.3 J K-1 mol-1 
D)  -583.6 J K-1 mol-1 
E)  +2334.6 J K-1 mol-1

Question 8

Match the following.
-Q < K

Accepted Answer

A) standard state 
B) equilibrium 
C) ΔrG > ΔrG° 
D) ΔrG > 0 
E) DrG rG rG° 
A) standard state 
B) equilibrium 
C) ΔrG > ΔrG° 
D) ΔrG > 0 
E) DrG rG rG°

Question 9

Place the following in order of decreasing standard molar entropy. NaCl(s) Na3PO4(aq) NaCl(aq)

Accepted Answer

A)  NaCl(s) > NaCl(aq) > Na3PO4(aq) 
B)  NaCl(aq) > NaCl(s) > Na3PO4(aq) 
C)  Na3PO4(aq) > NaCl(aq) > NaCl(s) 
D)  NaCl(s) > Na3PO4(aq) > NaCl(aq) 
E)  NaCl(aq) > Na3PO4(aq) > NaCl(s) 
A)  NaCl(s) > NaCl(aq) > Na3PO4(aq) 
B)  NaCl(aq) > NaCl(s) > Na3PO4(aq) 
C)  Na3PO4(aq) > NaCl(aq) > NaCl(s) 
D)  NaCl(s) > Na3PO4(aq) > NaCl(aq) 
E)  NaCl(aq) > Na3PO4(aq) > NaCl(s)

Question 10

Which of the following reactions will have the largest equilibrium constant (K) at 298 K?

Accepted Answer

A)  CaCO3(s) → CaO(s) + CO2(g) ΔrG° =+131.1 kJ mol-1 
B)  2 Hg(g) + O2(g) → 2HgO(s) ΔrG° = -180.8 kJ mol-1 
C)  3O2(g) → 2O3(g) ΔrG° = +326 kJ mol-1 
D)  Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) ΔrG° = -28.0 kJ mol-1 
A)  CaCO3(s) → CaO(s) + CO2(g) ΔrG° =+131.1 kJ mol-1 
B)  2 Hg(g) + O2(g) → 2HgO(s) ΔrG° = -180.8 kJ mol-1 
C)  3O2(g) → 2O3(g) ΔrG° = +326 kJ mol-1 
D)  Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) ΔrG° = -28.0 kJ mol-1

Question 11

Calculate ΔrG at 298 K under the conditions shown below for the following reaction: Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) ΔG° = -28.0 kJ mol-1
P(CO) = 1.4 atm, P(CO2) = 2.1 atm

Accepted Answer

A)  +31.0 kJ mol-1 
B)  +2.99 kJ mol-1 
C)  -30.7 kJ mol-1 
D)  +17.5 kJ mol-1 
E)  -25.0 kJ mol-1 
A)  +31.0 kJ mol-1 
B)  +2.99 kJ mol-1 
C)  -30.7 kJ mol-1 
D)  +17.5 kJ mol-1 
E)  -25.0 kJ mol-1

Question 12

Which of the following relationships is correct at constant T and P?

Accepted Answer

A)  ΔrG is proportional to -ΔSuniv. 
B)  ΔrG > 0 represents a spontaneous process. 
C)  ΔrG > 0 represents an increase in kinetic energy. 
D)  ΔrG rG is not a function of temperature. 
A)  ΔrG is proportional to -ΔSuniv. 
B)  ΔrG > 0 represents a spontaneous process. 
C)  ΔrG > 0 represents an increase in kinetic energy. 
D)  ΔrG rG is not a function of temperature.

Question 13

Consider a reaction that has a negative ΔrH and a negative ΔrS. Which of the following statements is TRUE?

Accepted Answer

A)  This reaction will be spontaneous only at high temperatures. 
B)  This reaction will be spontaneous at all temperatures. 
C)  This reaction will be nonspontaneous at all temperatures. 
D)  This reaction will be nonspontaneous only at high temperatures. 
E)  This reaction will be spontaneous only at absolute zero (0 Kelvin). 
A)  This reaction will be spontaneous only at high temperatures. 
B)  This reaction will be spontaneous at all temperatures. 
C)  This reaction will be nonspontaneous at all temperatures. 
D)  This reaction will be nonspontaneous only at high temperatures. 
E)  This reaction will be spontaneous only at absolute zero (0 Kelvin).

Question 14

Estimate ΔrG° for the following reaction at 775 K. 2Hg(g) + O2(g) → 2HgO(s) ΔrH°= -304.2 kJ mol-1; ΔrS°= -414.2 J K-1 mol-1

Accepted Answer

A)  -625 kJ mol-1 
B)  -181 kJ mol-1 
C)  +17 kJ mol-1 
D)  +321 kJ mol-1 
E)  -110 kJ mol-1 
A)  -625 kJ mol-1 
B)  -181 kJ mol-1 
C)  +17 kJ mol-1 
D)  +321 kJ mol-1 
E)  -110 kJ mol-1

Question 15

What is the change in Gibbs energy of a process?

Accepted Answer

A)  It is a maximum amount of energy available to do work. 
B)  It is energy that is lost to the surroundings. 
C)  It is energy that is used to break chemical bonds. 
D)  It is energy that is converted to heat. 
E)  It is the total energy of a process. 
A)  It is a maximum amount of energy available to do work. 
B)  It is energy that is lost to the surroundings. 
C)  It is energy that is used to break chemical bonds. 
D)  It is energy that is converted to heat. 
E)  It is the total energy of a process.

Question 16

Given the following equation, N2O(g) + NO2(g) → 3NO(g) ΔrG° = -23.0 kJ mol-1
Calculate ΔrG° for the following reaction:
3N2O(g) + 3NO2(g) → 9NO(g)

Accepted Answer

A)  -23.0 kJ mol-1 
B)  69.0 kJ mol-1 
C)  -69.0 kJ mol-1 
D)  -7.67 kJ mol-1 
E)  23.0 kJ mol-1 
A)  -23.0 kJ mol-1 
B)  69.0 kJ mol-1 
C)  -69.0 kJ mol-1 
D)  -7.67 kJ mol-1 
E)  23.0 kJ mol-1

Question 17

Calculate ΔrG° at 298 K using the following information: 2H2S(g) + 3O2(g) → 2SO2(g) + 2H2O(g) ΔrG° = ?
ΔfH° (kJ mol-1) -20.6 -296.8 -241.8
S°(J K-1 mol-1) 205.8 205.2 248.2 188.8

Accepted Answer

A)  -990.3 kJ mol-1 
B)  +108.2 kJ mol-1 
C)  -466.1 kJ mol-1 
D)  +676.2 kJ mol-1 
E)  -147.1 kJ mol-1 
A)  -990.3 kJ mol-1 
B)  +108.2 kJ mol-1 
C)  -466.1 kJ mol-1 
D)  +676.2 kJ mol-1 
E)  -147.1 kJ mol-1

Question 18

Place the following in order of increasing standard molar entropy. H2O(l) H2O(g) H2O(s)

Accepted Answer

A)  H2O(g) 2O(l) 2O(s) 
B)  H2O(s) 2O(l) 2O(g) 
C)  H2O(g) 2O(s) 2O(l) 
D)  H2O(l) 2O(s) 2O(g) 
E)  H2O(s) 2O(g) 2O(l) 
A)  H2O(g) 2O(l) 2O(s) 
B)  H2O(s) 2O(l) 2O(g) 
C)  H2O(g) 2O(s) 2O(l) 
D)  H2O(l) 2O(s) 2O(g) 
E)  H2O(s) 2O(g) 2O(l)

Question 19

In the Haber process, ammonia is synthesized from nitrogen and hydrogen:   (g) +   (g) →   (g) ΔrG° at 298 K for this reaction is -33.3 kJ mol-1. The value of ΔrG at 298 K for a reaction mixture that consists of 1.7 atm   , 1.1 atm   , and 0.55 atm   is ________ kJ mol-1.

Accepted Answer

A)  -5.02 × 103 
B)  -4.5 
C)  -72.2 
D)  -35.3 
E)  -38.3 
A)  -5.02 × 103 
B)  -4.5 
C)  -72.2 
D)  -35.3 
E)  -38.3

Question 20

Which of the following processes shows a decrease in entropy of the system?

Accepted Answer

A)  2NO(g) + O2(g) → 2NO2(g) 
B)  COCl2(g) → CO(g) + Cl2(g) 
C)  CH3OH(l) → CO(g) + 2H2(g) 
D)  NaClO3(s) → Na+(aq) + ClO3-(aq) 
E)  H2(g) + Cl2(g) → 2HCl(g) 
A)  2NO(g) + O2(g) → 2NO2(g) 
B)  COCl2(g) → CO(g) + Cl2(g) 
C)  CH3OH(l) → CO(g) + 2H2(g) 
D)  NaClO3(s) → Na+(aq) + ClO3-(aq) 
E)  H2(g) + Cl2(g) → 2HCl(g)

Exam 17: Gibbs Energy and Thermodynamics

Why can endothermic reactions be spontaneous?

Consider the following reaction at constant pressure. Use the information here to determine the value of ΔSsurr at 398 K. Predict whether or not this reaction will be spontaneous at this temperature. 4NH3(g) + 3O2(g) → 2N2(g) + 6H2O(g) ΔrH = -1267 kJ

Which of the following statements is TRUE?

Choose the statement below that is TRUE.

Consider a reaction that has a negative ΔrH and a positive ΔrS. Which of the following statements is TRUE?

Calculate ΔrG at 298 K under the conditions shown below for the following reaction: 3O2(g) → 2O3(g) ΔrG° = +326 kJ P(O2) = 0.41 atm, P(O3) = 5.2 atm

Calculate ΔρS° for the following reaction. The S° for each species is shown below the reaction. P4(g) + 10Cl2(g) → 4PCl5(g) S°(J K-1 mol-1) 280.0 223.1 364.6

Match the following. -Q < K

Place the following in order of decreasing standard molar entropy. NaCl(s) Na3PO4(aq) NaCl(aq)

Which of the following reactions will have the largest equilibrium constant (K) at 298 K?

Calculate ΔrG at 298 K under the conditions shown below for the following reaction: Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) ΔG° = -28.0 kJ mol-1 P(CO) = 1.4 atm, P(CO2) = 2.1 atm

Which of the following relationships is correct at constant T and P?

Consider a reaction that has a negative ΔrH and a negative ΔrS. Which of the following statements is TRUE?

Estimate ΔrG° for the following reaction at 775 K. 2Hg(g) + O2(g) → 2HgO(s) ΔrH°= -304.2 kJ mol-1; ΔrS°= -414.2 J K-1 mol-1

What is the change in Gibbs energy of a process?

Given the following equation, N2O(g) + NO2(g) → 3NO(g) ΔrG° = -23.0 kJ mol-1 Calculate ΔrG° for the following reaction: 3N2O(g) + 3NO2(g) → 9NO(g)

Calculate ΔrG° at 298 K using the following information: 2H2S(g) + 3O2(g) → 2SO2(g) + 2H2O(g) ΔrG° = ? ΔfH° (kJ mol-1) -20.6 -296.8 -241.8 S°(J K-1 mol-1) 205.8 205.2 248.2 188.8

Place the following in order of increasing standard molar entropy. H2O(l) H2O(g) H2O(s)

In the Haber process, ammonia is synthesized from nitrogen and hydrogen: (g) + (g) → (g) ΔrG° at 298 K for this reaction is -33.3 kJ mol-1. The value of ΔrG at 298 K for a reaction mixture that consists of 1.7 atm , 1.1 atm , and 0.55 atm is ________ kJ mol-1.

Which of the following processes shows a decrease in entropy of the system?

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Consider the following reaction at constant pressure. Use the information here to determine the value of ΔS_surr at 398 K. Predict whether or not this reaction will be spontaneous at this temperature. 4NH₃(g) + 3O₂(g) → 2N₂(g) + 6H₂O(g) Δ_rH = -1267 kJ

Consider a reaction that has a negative Δ_rH and a positive Δ_rS. Which of the following statements is TRUE?

Calculate Δ_rG at 298 K under the conditions shown below for the following reaction: 3O₂(g) → 2O₃(g) Δ_rG° = +326 kJ P(O₂) = 0.41 atm, P(O₃) = 5.2 atm

Calculate ΔρS° for the following reaction. The S° for each species is shown below the reaction. P₄(g) + 10Cl₂(g) → 4PCl₅(g) S°(J K^-1 mol^-1) 280.0 223.1 364.6

Place the following in order of decreasing standard molar entropy. NaCl(s) Na₃PO₄(aq) NaCl(aq)

Calculate Δ_rG at 298 K under the conditions shown below for the following reaction: Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g) ΔG° = -28.0 kJ mol^-1 P(CO) = 1.4 atm, P(CO₂) = 2.1 atm

Consider a reaction that has a negative Δ_rH and a negative Δ_rS. Which of the following statements is TRUE?

Estimate Δ_rG° for the following reaction at 775 K. 2Hg(g) + O₂(g) → 2HgO(s) Δ_rH°= -304.2 kJ mol^-1; Δ_rS°= -414.2 J K^-1 mol^-1

Given the following equation, N₂O(g) + NO₂(g) → 3NO(g) Δ_rG° = -23.0 kJ mol^-1 Calculate Δ_rG° for the following reaction: 3N₂O(g) + 3NO₂(g) → 9NO(g)

Calculate Δ_rG° at 298 K using the following information: 2H₂S(g) + 3O₂(g) → 2SO₂(g) + 2H₂O(g) Δ_rG°= ? Δ_fH° (kJ mol^-1) -20.6 -296.8 -241.8 S°(J K^-1 mol^-1) 205.8 205.2 248.2 188.8

Place the following in order of increasing standard molar entropy. H₂O(l) H₂O(g) H₂O(s)

In the Haber process, ammonia is synthesized from nitrogen and hydrogen: (g) + (g) → (g) Δ_rG° at 298 K for this reaction is -33.3 kJ mol^-1. The value of Δ_rG at 298 K for a reaction mixture that consists of 1.7 atm , 1.1 atm , and 0.55 atm is ________ kJ mol^-1.