Question 1

If ΔG° = 0,then

Accepted Answer

A)  K = 0. 
B)  K < 0. 
C)  K < 1. 
D)  K = 1. 
E)  K < −1. 
A)  K = 0. 
B)  K < 0. 
C)  K < 1. 
D)  K = 1. 
E)  K < −1.

Question 2

Calculate ΔS° for the evaporation of water,given S°[H2O(l)] = +69.9 J/mol⋅K and S°[H2O(g)] = +188.7 J/mol⋅K.

Accepted Answer

A)  −258.6 J/K 
B)  −118.8 J/K 
C)  0.0000 J/K 
D)  +118.8 J/K 
E)  +258.6 J/K 
A)  −258.6 J/K 
B)  −118.8 J/K 
C)  0.0000 J/K 
D)  +118.8 J/K 
E)  +258.6 J/K

Question 3

Ammonia is synthesized from nitrogen and hydrogen gases at a temperature of 475°C. N2(g)+ 3H2(g)→ 2NH3(g) 
If ΔH° = −92.2 kJ and ΔS° = −0.1987 kJ/K,what is ΔG° for the reaction at 575°C?

Accepted Answer

A)  −260.7 kJ 
B)  −186.6 kJ 
C)  −92.0 kJ 
D)  +2.2 kJ 
E)  +76.3 kJ 
A)  −260.7 kJ 
B)  −186.6 kJ 
C)  −92.0 kJ 
D)  +2.2 kJ 
E)  +76.3 kJ

Question 4

Which of the following reactions is likely to have the most positive change in entropy?

Accepted Answer

A)  N2(g)+ 3H2(g)→ 2NH3(g) 
B)  N2(g)+ 2O2(g)→ 2NO2(g) 
C)  2C(s)+ O2(g)→ 2CO(g) 
D)  C(s)+ O2(g)→ CO2(g) 
E)  CaO(s)+ CO2(g)→ CaCO3(s) 
A)  N2(g)+ 3H2(g)→ 2NH3(g) 
B)  N2(g)+ 2O2(g)→ 2NO2(g) 
C)  2C(s)+ O2(g)→ 2CO(g) 
D)  C(s)+ O2(g)→ CO2(g) 
E)  CaO(s)+ CO2(g)→ CaCO3(s)

Question 5

Given that S(g)+ O2(g)? SO2(g)
?G° = -300.1 kJ
2S(g)+ 3O2(g)? 2SO3(g)
?G° = -742.1 kJ
Calculate $\Delta G_{f}^{\circ}$ of the following reaction:
SO2(g)+ 1/2O2(g)? SO3(g)

Accepted Answer

A)  -1042.2 kJ 
B)  -71.0 kJ 
C)  +2.47 kJ 
D)  +71.0 kJ 
E)  +1042.2 kJ 
A)  -1042.2 kJ 
B)  -71.0 kJ 
C)  +2.47 kJ 
D)  +71.0 kJ 
E)  +1042.2 kJ

Question 6

If a chemical reaction has a negative change in entropy,ΔS,then

Accepted Answer

A)  the reaction is endothermic. 
B)  the reaction is spontaneous. 
C)  the equilibrium constant is greater than 1. 
D)  there is an increase in the order of the system. 
E)  the change in Gibbs free energy,ΔG,is negative. 
A)  the reaction is endothermic. 
B)  the reaction is spontaneous. 
C)  the equilibrium constant is greater than 1. 
D)  there is an increase in the order of the system. 
E)  the change in Gibbs free energy,ΔG,is negative.

Question 7

What is ΔG° at 555°C for a reaction with ΔH° = −152 kJ and ΔS° = 79.1 J/K?

Accepted Answer

A)  −4370 kJ 
B)  −217 kJ 
C)  −196 kJ 
D)  +196 kJ 
E)  + 643 kJ 
A)  −4370 kJ 
B)  −217 kJ 
C)  −196 kJ 
D)  +196 kJ 
E)  + 643 kJ

Question 8

At 25°C,the acid dissociation constant for formic acid is 6.9 × 10−4.Calculate ΔG° for this reaction.(R = 8.31 × 10−3 kJ/K)

Accepted Answer

A)  −18.0 kJ 
B)  −1.51 kJ 
C)  +1.51 kJ 
D)  +18.0 kJ 
E)  +41.4 kJ 
A)  −18.0 kJ 
B)  −1.51 kJ 
C)  +1.51 kJ 
D)  +18.0 kJ 
E)  +41.4 kJ

Question 9

The standard free energy change for a chemical reaction is +13.3 kJ.What is the equilibrium constant for the reaction at 125°C? (R = 8.31 × 10−3 kJ/K)

Accepted Answer

A)  2.8 × 10-6 
B)  2.0 × 10-5 
C)  4.7 × 10-3 
D)  1.8 × 10-2 
E)  2.1 × 102 
A)  2.8 × 10-6 
B)  2.0 × 10-5 
C)  4.7 × 10-3 
D)  1.8 × 10-2 
E)  2.1 × 102

Question 10

For the dimerization of nitrogen dioxide,ΔG° = −4.7 kJ at 25°C. 2NO2(g)→ N2O4(g), Calculate ΔG for this reaction if the partial pressures of NO2 and N2O4 are both 0.50 atm.(R = 8.31 × 10−3 kJ/K)

Accepted Answer

A)  −6.4 kJ 
B)  −4.8 kJ 
C)  −4.7 kJ 
D)  −4.6 kJ 
E)  −3.0 kJ 
A)  −6.4 kJ 
B)  −4.8 kJ 
C)  −4.7 kJ 
D)  −4.6 kJ 
E)  −3.0 kJ

Question 11

Calculate ?S° for the dissociation of dinitrogen tetraoxide at 25°C. N2O4(g)? 2NO2(g)
$\begin{array}{lll}
\text { Substance } & \Delta G_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) & \Delta H_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) \
\hline \mathrm{NO}_{2}(g) & +51.3 & +33.2 \
\mathrm{~N}_{2} \mathrm{O}_{4}(g) & +97.9 & +9.2
\end{array}$

Accepted Answer

A)  ?2.10 kJ/K 
B)  ?0.550 kJ/K 
C)  ?0.208 kJ/K 
D)  +0.076 kJ/K 
E)  +2.10 kJ/K 
A)  ?2.10 kJ/K 
B)  ?0.550 kJ/K 
C)  ?0.208 kJ/K 
D)  +0.076 kJ/K 
E)  +2.10 kJ/K

Question 12

The standard free energy change associated with the dissolution of ammonium nitrate in water is -6.73 kJ at 298 K. NH4NO3(s)  ? NH4NO3(aq)
What is the equilibrium constant for the reaction? (R = 8.31 × 10?3 kJ/K)

Accepted Answer

A)  1.9 × 10-3 
B)  6.6 × 10-2 
C)  1.0 
D)  15 
E)  5.2 × 102 
A)  1.9 × 10-3 
B)  6.6 × 10-2 
C)  1.0 
D)  15 
E)  5.2 × 102

Question 13

At 298 K,all of the following substances have a standard free energy of formation of zero EXCEPT ____.

Accepted Answer

A)  Br2(g) 
B)  I2(s) 
C)  S8(s) 
D)  Cl2(g) 
E)  Hg(l) 
A)  Br2(g) 
B)  I2(s) 
C)  S8(s) 
D)  Cl2(g) 
E)  Hg(l)

Question 14

In a gas phase reaction,what is the effect of increasing reactant or product pressure on the standard Gibbs free energy,ΔG°?

Accepted Answer

A)  ΔG° increases due to decreased entropy. 
B)  ΔG° decreases due to decreased entropy. 
C)  ΔG° increases due to increased enthalpy. 
D)  ΔG° may either increase or decrease. 
E)  ΔG° is unchanged. 
A)  ΔG° increases due to decreased entropy. 
B)  ΔG° decreases due to decreased entropy. 
C)  ΔG° increases due to increased enthalpy. 
D)  ΔG° may either increase or decrease. 
E)  ΔG° is unchanged.

Question 15

Given that,at 25°C, C(s)+ O2(g)→ CO2(g)
ΔG° = −394.4 kJ 
C(s)+ $\frac{1}{2}$ O2(g)→ CO(g)
ΔG° = −137.2 kJ
Calculate ΔG° for the reaction below.
CO(g)+ $\frac{1}{2}$ O2(g)→ CO2(g)

Accepted Answer

A)  −531.6 kJ 
B)  −257.2 kJ 
C)  −171.5 kJ 
D)  +141.2 kJ 
E)  +531.6 kJ 
A)  −531.6 kJ 
B)  −257.2 kJ 
C)  −171.5 kJ 
D)  +141.2 kJ 
E)  +531.6 kJ

Question 16

If ΔG is positive at all temperatures,then which of the following statements must be true?

Accepted Answer

A) ΔH 0 D) ΔH > 0 and ΔS > 0 E) ΔH > 0 and ΔS < 0 A) ΔH 0 D) ΔH > 0 and ΔS > 0 E) ΔH > 0 and ΔS < 0

Question 17

All of the following events result in an increase in entropy EXCEPT

Accepted Answer

A)  the melting of candle wax. 
B)  the combustion of carbon. 
C)  the dissolution of sodium chloride in water. 
D)  the evaporation of ethanol. 
E)  the formation of N2O4(g)from NO2(g). 
A)  the melting of candle wax. 
B)  the combustion of carbon. 
C)  the dissolution of sodium chloride in water. 
D)  the evaporation of ethanol. 
E)  the formation of N2O4(g)from NO2(g).

Question 18

If a chemical reaction is exothermic,but not spontaneous,which of the following must be true?

Accepted Answer

A) ΔG > 0,ΔS > 0 and ΔH > 0 B) ΔG 0 and ΔH > 0 C) ΔG > 0,ΔS 0 D) ΔG 0,ΔS < 0 and ΔH < 0 A) ΔG > 0,ΔS > 0 and ΔH > 0 B) ΔG 0 and ΔH > 0 C) ΔG > 0,ΔS 0 D) ΔG 0,ΔS < 0 and ΔH < 0

Question 19

Calculate ?G° for the reaction below at 25.0°C. 
P4O10(s)+ 6H2O(l)? 4H3PO4(l)
$\begin{array}{lll}
\text { Species } & \Delta H_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) & S^{\circ}(\mathrm{J} / \mathrm{mol} \cdot \mathrm{K}) \
\hline \mathrm{P}_{4} \mathrm{O}_{10}(s) & -2984.0 & 228.9 \
\mathrm{H}_{2} \mathrm{O}(l) & -285.8 & 69.95 \
\mathrm{H}_{3} \mathrm{PO}_{4}(l) & -1279.0 & 110.5
\end{array}$

Accepted Answer

A)  -6119.1 kJ 
B)  -632.8 kJ 
C)  -355.6 kJ 
D)  +210.6 kJ 
E)  +6119.1 kJ 
A)  -6119.1 kJ 
B)  -632.8 kJ 
C)  -355.6 kJ 
D)  +210.6 kJ 
E)  +6119.1 kJ

Question 20

Predict the signs of ΔS and ΔH for the evaporation of water at 295 K.

Accepted Answer

A) ΔH = 0 and ΔS > 0 B) ΔH > 0 and ΔS 0 and ΔS > 0 D) ΔH 0 E) ΔH < 0 and ΔS < 0 A) ΔH = 0 and ΔS > 0 B) ΔH > 0 and ΔS 0 and ΔS > 0 D) ΔH 0 E) ΔH < 0 and ΔS < 0

Exam 16: Spontaneity of Reaction

If ΔG° = 0,then

Calculate ΔS° for the evaporation of water,given S°[H2O(l)] = +69.9 J/mol⋅K and S°[H2O(g)] = +188.7 J/mol⋅K.

Ammonia is synthesized from nitrogen and hydrogen gases at a temperature of 475°C. N2(g)+ 3H2(g)→ 2NH3(g) If ΔH° = −92.2 kJ and ΔS° = −0.1987 kJ/K,what is ΔG° for the reaction at 575°C?

Which of the following reactions is likely to have the most positive change in entropy?

Given that S(g)+ O2(g)? SO2(g) ?G° = -300.1 kJ 2S(g)+ 3O2(g)? 2SO3(g) ?G° = -742.1 kJ Calculate ΔGf∘\Delta G_{f}^{\circ}ΔGf∘​ of the following reaction: SO2(g)+ 1/2O2(g)? SO3(g)

If a chemical reaction has a negative change in entropy,ΔS,then

What is ΔG° at 555°C for a reaction with ΔH° = −152 kJ and ΔS° = 79.1 J/K?

At 25°C,the acid dissociation constant for formic acid is 6.9 × 10−4.Calculate ΔG° for this reaction.(R = 8.31 × 10−3 kJ/K)

The standard free energy change for a chemical reaction is +13.3 kJ.What is the equilibrium constant for the reaction at 125°C? (R = 8.31 × 10−3 kJ/K)

For the dimerization of nitrogen dioxide,ΔG° = −4.7 kJ at 25°C. 2NO2(g)→ N2O4(g), Calculate ΔG for this reaction if the partial pressures of NO2 and N2O4 are both 0.50 atm.(R = 8.31 × 10−3 kJ/K)

Calculate ?S° for the dissociation of dinitrogen tetraoxide at 25°C. N2O4(g)? 2NO2(g) Substance \Delta(/) \Delta(/) (g) +51.3 +33.2 (g) +97.9 +9.2

The standard free energy change associated with the dissolution of ammonium nitrate in water is -6.73 kJ at 298 K. NH4NO3(s) ? NH4NO3(aq) What is the equilibrium constant for the reaction? (R = 8.31 × 10?3 kJ/K)

At 298 K,all of the following substances have a standard free energy of formation of zero EXCEPT ____.

In a gas phase reaction,what is the effect of increasing reactant or product pressure on the standard Gibbs free energy,ΔG°?

Given that,at 25°C, C(s)+ O2(g)→ CO2(g) ΔG° = −394.4 kJ C(s)+ 12\frac{1}{2}21​ O2(g)→ CO(g) ΔG° = −137.2 kJ Calculate ΔG° for the reaction below. CO(g)+ 12\frac{1}{2}21​ O2(g)→ CO2(g)

If ΔG is positive at all temperatures,then which of the following statements must be true?

All of the following events result in an increase in entropy EXCEPT

If a chemical reaction is exothermic,but not spontaneous,which of the following must be true?

Calculate ?G° for the reaction below at 25.0°C. P4O10(s)+ 6H2O(l)? 4H3PO4(l) Species \Delta(/) (/\cdot) (s) -2984.0 228.9 (l) -285.8 69.95 (l) -1279.0 110.5

Predict the signs of ΔS and ΔH for the evaporation of water at 295 K.

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Calculate ΔS° for the evaporation of water,given S°[H₂O(l)] = +69.9 J/mol⋅K and S°[H₂O(g)] = +188.7 J/mol⋅K.

Ammonia is synthesized from nitrogen and hydrogen gases at a temperature of 475°C. N₂(g)+ 3H₂(g)→ 2NH₃(g) If ΔH° = −92.2 kJ and ΔS° = −0.1987 kJ/K,what is ΔG° for the reaction at 575°C?

Given that S(g)+ O₂(g)? SO₂(g) ?G° = -300.1 kJ 2S(g)+ 3O₂(g)? 2SO₃(g) ?G° = -742.1 kJ Calculate $\Delta G_{f}^{\circ}$ of the following reaction: SO₂(g)+ 1/2O₂(g)? SO₃(g)

At 25°C,the acid dissociation constant for formic acid is 6.9 × 10−⁴.Calculate ΔG° for this reaction.(R = 8.31 × 10−³ kJ/K)

The standard free energy change for a chemical reaction is +13.3 kJ.What is the equilibrium constant for the reaction at 125°C? (R = 8.31 × 10−³ kJ/K)

For the dimerization of nitrogen dioxide,ΔG° = −4.7 kJ at 25°C. 2NO₂(g)→ N₂O₄(g), Calculate ΔG for this reaction if the partial pressures of NO₂ and N₂O₄ are both 0.50 atm.(R = 8.31 × 10−³ kJ/K)

Calculate ?S° for the dissociation of dinitrogen tetraoxide at 25°C. N₂O₄(g)? 2NO₂(g) Substance \Delta(/) \Delta(/) (g) +51.3 +33.2 (g) +97.9 +9.2

The standard free energy change associated with the dissolution of ammonium nitrate in water is -6.73 kJ at 298 K. NH₄NO₃(s) ? NH₄NO₃(aq) What is the equilibrium constant for the reaction? (R = 8.31 × 10?³ kJ/K)

Given that,at 25°C, C(s)+ O₂(g)→ CO₂(g) ΔG° = −394.4 kJ C(s)+ $\frac{1}{2}$ O₂(g)→ CO(g) ΔG° = −137.2 kJ Calculate ΔG° for the reaction below. CO(g)+ $\frac{1}{2}$ O₂(g)→ CO₂(g)

Calculate ?G° for the reaction below at 25.0°C. P₄O₁₀(s)+ 6H₂O(l)? 4H₃PO₄(l) Species \Delta(/) (/\cdot) (s) -2984.0 228.9 (l) -285.8 69.95 (l) -1279.0 110.5