Question 1

For which of the following reactions will the entropy of the system decrease?

Accepted Answer

A)  2NH3(g)→ N2(g)+ 3H2(g) 
B)  2C(s)+ O2(g)→ 2CO(g) 
C)  CaCO3(s)→ CaO(s)+ CO2(g) 
D)  2NO2(g)→ N2O4(g) 
E)  NaOH(s)→ Na+(aq)+ OH-(aq) 
A)  2NH3(g)→ N2(g)+ 3H2(g) 
B)  2C(s)+ O2(g)→ 2CO(g) 
C)  CaCO3(s)→ CaO(s)+ CO2(g) 
D)  2NO2(g)→ N2O4(g) 
E)  NaOH(s)→ Na+(aq)+ OH-(aq) D

Question 2

For the decomposition of calcium carbonate,ΔG° = +130.4 kJ at 25°C. CaCO3(s)→ CaO(s)+ CO2(g)
Calculate the partial pressure of CO2 if ΔG = 0.0 kJ.(R = 8.31 × 10−3 kJ/K)

Accepted Answer

A)  1.3 × 10−23 atm 
B)  2.7 × 102 atm 
C)  8.2 × 10−5 atm 
D)  5.3 × 101 atm 
E)  7.4 × 1022 atm 
A)  1.3 × 10−23 atm 
B)  2.7 × 102 atm 
C)  8.2 × 10−5 atm 
D)  5.3 × 101 atm 
E)  7.4 × 1022 atm A

Question 3

Calculate ?G° for the following reaction at 298 K. S(s)+ O2(g)? SO2(g)
$\begin{array}{l}

\begin{array}{lll}
\text { Substance } & \Delta H_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) &S^{\circ}(\mathrm{kJ} / \mathrm{mol} . \mathrm{K})\
\hline \mathrm{S}(s) & 0.0 & +0.0318 \
\mathrm{O}_{2}(g) & 0.0 & +0.2050 \
\mathrm{SO}_{2}(g) & -296.8 & +0.2481
\end{array}
\end{array}$

Accepted Answer

A)  ?300.2 kJ 
B)  ?296.8 kJ 
C)  ?85.1 kJ 
D)  +29.3 kJ 
E)  +145.7 kJ 
A)  ?300.2 kJ 
B)  ?296.8 kJ 
C)  ?85.1 kJ 
D)  +29.3 kJ 
E)  +145.7 kJ A

Question 4

In what temperature range is ΔG° greater than zero for the formation of NH4Cl(s)from NH3(g)and HCl(g)? 
NH3(g)+ HCl(g)→ NH4Cl(s)
For the reaction,ΔH° = −176.0 kJ and ΔS° = −0.2845 kJ/K.

Accepted Answer

A)  The temperature must be greater than 619 K. 
B)  The temperature must be less than 619 K. 
C)  The temperature must be exactly 619 K. 
D)  ΔG° is always greater than zero. 
E)  ΔG° is never greater than zero. 
A)  The temperature must be greater than 619 K. 
B)  The temperature must be less than 619 K. 
C)  The temperature must be exactly 619 K. 
D)  ΔG° is always greater than zero. 
E)  ΔG° is never greater than zero.

Question 5

Calculate ΔS° for the following reaction, H2(g)+ Br2(l)→ 2HBr(g)
Given S°[H2(g)] = +131 J/mol⋅K,S°[Br2(l)] = +152 J/mol⋅K,and S°[HBr(g)] = +199 J/mol⋅K.

Accepted Answer

A)  −84 J/K 
B)  +84 J/K 
C)  +115 J/K 
D)  +482 J/K 
E)  +681 J/K 
A)  −84 J/K 
B)  +84 J/K 
C)  +115 J/K 
D)  +482 J/K 
E)  +681 J/K

Question 6

Calculate ΔG° for the reaction below at 25.0°C CS2(g)+ 3Cl2(g)→ S2Cl2(g)+ CCl4(g), Given ΔH° = -231.1 kJ and ΔS° = -287.6 J/K.

Accepted Answer

A)  -518.7 kJ 
B)  -316.9 kJ 
C)  -145.4 kJ 
D)  -56.5 kJ 
E)  +56.5 kJ 
A)  -518.7 kJ 
B)  -316.9 kJ 
C)  -145.4 kJ 
D)  -56.5 kJ 
E)  +56.5 kJ

Question 7

When a real gas is compressed from low pressure to a higher pressure,its temperature increases.Predict the signs of ΔH and ΔS.

Accepted Answer

A) ΔH 0 C) ΔH > 0 and ΔS 0 and ΔS > 0 E) ΔH < 0 and ΔS = 0 A) ΔH 0 C) ΔH > 0 and ΔS 0 and ΔS > 0 E) ΔH < 0 and ΔS = 0

Question 8

Calculate ΔS° for the following reaction, 2SO2(g)+ O2(g)→ 2SO3(g)
Given S°[SO2(g)] = 248.2 J/mol⋅K,S°[O2(g)] = 205.1 J/mol⋅K,and S°[SO3(g)] = 256.8 J/mol⋅K.

Accepted Answer

A)  -196.5 J/K 
B)  -94.0 J/K 
C)  -187.9 J/K 
D)  +187.9 J/K 
E)  +196.5 J/K 
A)  -196.5 J/K 
B)  -94.0 J/K 
C)  -187.9 J/K 
D)  +187.9 J/K 
E)  +196.5 J/K

Question 9

Diluting concentrated sulfuric acid with water can be dangerous.The temperature of the solution can increase rapidly.What are the signs of ΔH,ΔS,and ΔG for this process?

Accepted Answer

A)  ΔH  0,ΔG  0,ΔG > 0 
D)  ΔH > 0,ΔS > 0,ΔG  0,ΔS  0 
A)  ΔH  0,ΔG  0,ΔG > 0 
D)  ΔH > 0,ΔS > 0,ΔG  0,ΔS  0

Question 10

Calculate $\Delta G_{f}^{\circ}$ at 325 K for ethylene,C2H4(g),given the thermodynamic data below. 
$\begin{array}{l}

\begin{array}{lll}
\text { Substance } & \Delta H_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) &S^{\circ}(\mathrm{kJ} / \mathrm{mol} \cdot \mathrm{K})\
\hline \mathrm{C}(s) & 0.0 & +0.0057 \
\mathrm{H}_{2}(g) & 0.0 & +0.1306 \
\mathrm{C}_{2} \mathrm{H}_{4}(g) & +52.3 & +0.2195
\end{array}
\end{array}$

Accepted Answer

A)  ?47.1 kJ 
B)  ?19.0 kJ 
C)  +39.1 kJ 
D)  +52.1 kJ 
E)  +69.6 kJ 
A)  ?47.1 kJ 
B)  ?19.0 kJ 
C)  +39.1 kJ 
D)  +52.1 kJ 
E)  +69.6 kJ

Question 11

The dissolution of ammonium nitrate occurs spontaneously in water at 25°C.As NH4NO3 dissolves,the temperature of the water decreases.What are the signs of ΔH,ΔS,and ΔG for this process?

Accepted Answer

A)  ΔH > 0,ΔS  0 
B)  ΔH > 0,ΔS > 0,ΔG > 0 
C)  ΔH > 0,ΔS > 0,ΔG  0,ΔG > 0 
A)  ΔH > 0,ΔS  0 
B)  ΔH > 0,ΔS > 0,ΔG > 0 
C)  ΔH > 0,ΔS > 0,ΔG  0,ΔG > 0

Question 12

Ammonia is synthesized from nitrogen and hydrogen gases. N2(g)+ 3H2(g)→ 2NH3(g)
If ΔH° = −92.2 kJ and ΔS° = −0.1987 kJ/K,at what temperature will ΔG° = 0?

Accepted Answer

A)  0.00216 K 
B)  18.3 K 
C)  92.0 K 
D)  464 K 
E)  672 K 
A)  0.00216 K 
B)  18.3 K 
C)  92.0 K 
D)  464 K 
E)  672 K

Question 13

If ΔG is negative 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 14

Rubber elasticity is an entropic phenomenon.As a rubber band is stretched the entropy of the system

Accepted Answer

A)  is reduced. 
B)  is increased. 
C)  remains unchanged. 
D)  breaks the polymer chain. 
E)  causes chemical bonds to form. 
A)  is reduced. 
B)  is increased. 
C)  remains unchanged. 
D)  breaks the polymer chain. 
E)  causes chemical bonds to form.

Question 15

At what temperatures will a reaction be spontaneous if ΔH° = +62.4 kJ and ΔS° = +301 J/K?

Accepted Answer

A)  All temperatures below 207 K. 
B)  All temperatures above 207 K. 
C)  Temperatures between 179 K and 235 K. 
D)  The reaction will be spontaneous at any temperature. 
E)  The reaction will never be spontaneous. 
A)  All temperatures below 207 K. 
B)  All temperatures above 207 K. 
C)  Temperatures between 179 K and 235 K. 
D)  The reaction will be spontaneous at any temperature. 
E)  The reaction will never be spontaneous.

Question 16

All of the following statements are true EXCEPT

Accepted Answer

A) ΔS > 0 for systems that become more disorderly. B) reactions are spontaneous when ΔG < 0. C) reactions are spontaneous when ΔH < 0. D) ΔH < 0 for exothermic reactions. E) generally,nature tends to move from more ordered to more random states. A) ΔS > 0 for systems that become more disorderly. B) reactions are spontaneous when ΔG < 0. C) reactions are spontaneous when ΔH < 0. D) ΔH < 0 for exothermic reactions. E) generally,nature tends to move from more ordered to more random states.

Question 17

What is the correct form for the Gibbs-Helmholtz equation?

Accepted Answer

A)  ΔG = ΔH − TΔS 
B)  ΔG = ΔH + TΔS 
C)  ΔH = ΔG − TΔS 
D)  ΔS = ΔH − TΔG 
E)  ΔG = ΔS − TΔH 
A)  ΔG = ΔH − TΔS 
B)  ΔG = ΔH + TΔS 
C)  ΔH = ΔG − TΔS 
D)  ΔS = ΔH − TΔG 
E)  ΔG = ΔS − TΔH

Question 18

For the decomposition of hydrogen peroxide to water and oxygen, H2O2(g)→ H2O(g)+ $\frac{1}{2}$ O2(g)
ΔH° = −106 kJ,and ΔS° = +0.0580 kJ/K.Under which of the following conditions is the reaction spontaneous (ΔG° < 0)?

Accepted Answer

A)  The temperature must be greater than 1.83 × 103 K. 
B)  The temperature must be less than 1.83 × 103 K. 
C)  The temperature must be between 225 K and 1.83 × 103 K. 
D)  ΔG° is always less than zero. 
E)  ΔG° is never less than zero. 
A)  The temperature must be greater than 1.83 × 103 K. 
B)  The temperature must be less than 1.83 × 103 K. 
C)  The temperature must be between 225 K and 1.83 × 103 K. 
D)  ΔG° is always less than zero. 
E)  ΔG° is never less than zero.

Question 19

At 25°C,the equilibrium constant for the following reaction, 
Cu2+(aq)+ Zn(s)→ Cu(s)+ Zn2+(aq) Is 1.9 × 1037.
Calculate ΔG° for this reaction.(R = 8.31 × 10−3 kJ/K)

Accepted Answer

A)  −213 kJ 
B)  −145 kJ 
C)  −57.3 kJ 
D)  +57.3 kJ 
E)  +213 kJ 
A)  −213 kJ 
B)  −145 kJ 
C)  −57.3 kJ 
D)  +57.3 kJ 
E)  +213 kJ

Question 20

Calculate ?S° for the dissolution of BaCl2 in water at 25°C. BaCl2(s)? Ba2+(aq)+ 2Cl?(aq)
$\begin{array}{lll}
\text { Substance } & \Delta G_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) & \Delta H_{\mathrm{f}}^{0}(\mathrm{~kJ} / \mathrm{mol}) \
\hline \mathrm{BaCl}_{2}(s) & -810.4 & -858.6 \
\mathrm{Ba}^{2+}(a q) & -560.8 & -537.6 \
\mathrm{Cl}-(a q) & -131.2 & -167.2
\end{array}$

Accepted Answer

A)  ?0.20 kJ/K 
B)  ?0.14 kJ/K 
C)  ?0.0020 kJ/K 
D)  +0.12 kJ/K 
E)  +0.29 kJ/K 
A)  ?0.20 kJ/K 
B)  ?0.14 kJ/K 
C)  ?0.0020 kJ/K 
D)  +0.12 kJ/K 
E)  +0.29 kJ/K

Exam 16: Spontaneity of Reaction

For which of the following reactions will the entropy of the system decrease?

For the decomposition of calcium carbonate,ΔG° = +130.4 kJ at 25°C. CaCO3(s)→ CaO(s)+ CO2(g) Calculate the partial pressure of CO2 if ΔG = 0.0 kJ.(R = 8.31 × 10−3 kJ/K)

Calculate ?G° for the following reaction at 298 K. S(s)+ O2(g)? SO2(g) Substance \Delta(/) (/.) (s) 0.0 +0.0318 (g) 0.0 +0.2050 (g) -296.8 +0.2481

In what temperature range is ΔG° greater than zero for the formation of NH4Cl(s)from NH3(g)and HCl(g)? NH3(g)+ HCl(g)→ NH4Cl(s) For the reaction,ΔH° = −176.0 kJ and ΔS° = −0.2845 kJ/K.

Calculate ΔS° for the following reaction, H2(g)+ Br2(l)→ 2HBr(g) Given S°[H2(g)] = +131 J/mol⋅K,S°[Br2(l)] = +152 J/mol⋅K,and S°[HBr(g)] = +199 J/mol⋅K.

Calculate ΔG° for the reaction below at 25.0°C CS2(g)+ 3Cl2(g)→ S2Cl2(g)+ CCl4(g), Given ΔH° = -231.1 kJ and ΔS° = -287.6 J/K.

When a real gas is compressed from low pressure to a higher pressure,its temperature increases.Predict the signs of ΔH and ΔS.

Calculate ΔS° for the following reaction, 2SO2(g)+ O2(g)→ 2SO3(g) Given S°[SO2(g)] = 248.2 J/mol⋅K,S°[O2(g)] = 205.1 J/mol⋅K,and S°[SO3(g)] = 256.8 J/mol⋅K.

Diluting concentrated sulfuric acid with water can be dangerous.The temperature of the solution can increase rapidly.What are the signs of ΔH,ΔS,and ΔG for this process?

Calculate ΔGf∘\Delta G_{f}^{\circ}ΔGf∘​ at 325 K for ethylene,C2H4(g),given the thermodynamic data below. Substance \Delta(/) (/\cdot) (s) 0.0 +0.0057 (g) 0.0 +0.1306 (g) +52.3 +0.2195

The dissolution of ammonium nitrate occurs spontaneously in water at 25°C.As NH4NO3 dissolves,the temperature of the water decreases.What are the signs of ΔH,ΔS,and ΔG for this process?

Ammonia is synthesized from nitrogen and hydrogen gases. N2(g)+ 3H2(g)→ 2NH3(g) If ΔH° = −92.2 kJ and ΔS° = −0.1987 kJ/K,at what temperature will ΔG° = 0?

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

Rubber elasticity is an entropic phenomenon.As a rubber band is stretched the entropy of the system

At what temperatures will a reaction be spontaneous if ΔH° = +62.4 kJ and ΔS° = +301 J/K?

All of the following statements are true EXCEPT

What is the correct form for the Gibbs-Helmholtz equation?

For the decomposition of hydrogen peroxide to water and oxygen, H2O2(g)→ H2O(g)+ 12\frac{1}{2}21​ O2(g) ΔH° = −106 kJ,and ΔS° = +0.0580 kJ/K.Under which of the following conditions is the reaction spontaneous (ΔG° < 0)?

At 25°C,the equilibrium constant for the following reaction, Cu2+(aq)+ Zn(s)→ Cu(s)+ Zn2+(aq) Is 1.9 × 1037. Calculate ΔG° for this reaction.(R = 8.31 × 10−3 kJ/K)

Calculate ?S° for the dissolution of BaCl2 in water at 25°C. BaCl2(s)? Ba2+(aq)+ 2Cl?(aq) Substance \Delta(/) \Delta(/) (s) -810.4 -858.6 (aq) -560.8 -537.6 -(aq) -131.2 -167.2

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For the decomposition of calcium carbonate,ΔG° = +130.4 kJ at 25°C. CaCO₃(s)→ CaO(s)+ CO₂(g) Calculate the partial pressure of CO₂ if ΔG = 0.0 kJ.(R = 8.31 × 10−³ kJ/K)

Calculate ?G° for the following reaction at 298 K. S(s)+ O₂(g)? SO₂(g) Substance \Delta(/) (/.) (s) 0.0 +0.0318 (g) 0.0 +0.2050 (g) -296.8 +0.2481

In what temperature range is ΔG° greater than zero for the formation of NH₄Cl(s)from NH₃(g)and HCl(g)? NH₃(g)+ HCl(g)→ NH₄Cl(s) For the reaction,ΔH° = −176.0 kJ and ΔS° = −0.2845 kJ/K.

Calculate ΔS° for the following reaction, H₂(g)+ Br₂(l)→ 2HBr(g) Given S°[H₂(g)] = +131 J/mol⋅K,S°[Br₂(l)] = +152 J/mol⋅K,and S°[HBr(g)] = +199 J/mol⋅K.

Calculate ΔG° for the reaction below at 25.0°C CS₂(g)+ 3Cl₂(g)→ S₂Cl₂(g)+ CCl₄(g), Given ΔH° = -231.1 kJ and ΔS° = -287.6 J/K.

Calculate ΔS° for the following reaction, 2SO₂(g)+ O₂(g)→ 2SO₃(g) Given S°[SO₂(g)] = 248.2 J/mol⋅K,S°[O₂(g)] = 205.1 J/mol⋅K,and S°[SO₃(g)] = 256.8 J/mol⋅K.

Calculate $\Delta G_{f}^{\circ}$ at 325 K for ethylene,C₂H₄(g),given the thermodynamic data below. Substance \Delta(/) (/\cdot) (s) 0.0 +0.0057 (g) 0.0 +0.1306 (g) +52.3 +0.2195

The dissolution of ammonium nitrate occurs spontaneously in water at 25°C.As NH₄NO₃ dissolves,the temperature of the water decreases.What are the signs of ΔH,ΔS,and ΔG for this process?

Ammonia is synthesized from nitrogen and hydrogen gases. N₂(g)+ 3H₂(g)→ 2NH₃(g) If ΔH° = −92.2 kJ and ΔS° = −0.1987 kJ/K,at what temperature will ΔG° = 0?

For the decomposition of hydrogen peroxide to water and oxygen, H₂O₂(g)→ H₂O(g)+ $\frac{1}{2}$ O₂(g) ΔH° = −106 kJ,and ΔS° = +0.0580 kJ/K.Under which of the following conditions is the reaction spontaneous (ΔG° < 0)?

At 25°C,the equilibrium constant for the following reaction, Cu²⁺(aq)+ Zn(s)→ Cu(s)+ Zn²⁺(aq) Is 1.9 × 10³⁷. Calculate ΔG° for this reaction.(R = 8.31 × 10−³ kJ/K)

Calculate ?S° for the dissolution of BaCl₂ in water at 25°C. BaCl₂(s)? Ba²⁺(aq)+ 2Cl?(aq) Substance \Delta(/) \Delta(/) (s) -810.4 -858.6 (aq) -560.8 -537.6 -(aq) -131.2 -167.2