Deck 17: Entropy Free Energy and Equilibrium

Question 1

Which of these species has the highest entropy (S ^$\circ$ ) at 25 ^$\circ$ C

A) CH₃OH(l)
B) CO(g)
C) MgCO₃(s)
D) H₂O(l)
E) Ni(s)

Answer 1

CO(g)

Question 2

Aluminum forms a layer of aluminum oxide when exposed to air which protects the bulk metal from further corrosion.4Al(s) + 3O₂(g) $\rarr$ 2Al₂O₃(s) Using the thermodynamic data provided below, calculate $\Delta$ S ^$\circ$ for this reaction. $\begin{array}{|l|c|}\hline & \mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol}) \\\hline \mathrm{Al}(s) & 28.3 \\\hline \mathrm{O}_{2}(g) & 205.0 \\\hline \mathrm{Al}_{2} \mathrm{O}_{3}(s) & 50.99 \\\hline\end{array}$

A) 182.3 J/K·mol
B) 131.5 J/K·mol
C) -182.3 J/K·mol
D) -626.2 J/K·mol
E) -802.9 J/K·mol

Answer 2

D

Question 3

Which of these species would you expect to have the highest standard entropy (S ^$\circ$ )

A) CH₄(g)
B) C₂H₂(g)
C) C₂H₄(g)
D) C₂H₆(g)
E) C₃H₈(g)

Answer 3

C₃H₈(g)

Question 4

Which of the following processes would be accompanied by a decrease in entropy

A)H₂O(s) $\rarr$ H₂O(g)
B)H₂O(l) $\rarr$ H₂O(g)
C)H₂O(s) $\rarr$ H₂O(l)
D)H₂O(g) $\rarr$ H₂O(s)
E)H₂O(l, 50 ^$\circ$ C) $\rarr$ H₂O(l, 75 ^$\circ$ C)

Question 5

Which of the following processes would be accompanied by an increase in entropy

A)H₂O(g) $\rarr$ H₂O(s)
B)H₂O(l) $\rarr$ H₂O(s)
C)H₂O(g) $\rarr$ H₂O(l)
D)H₂O(s) $\rarr$ H₂O(g)
E) H₂O(l, 50 ^$\circ$ C) $\rarr$ H₂O(l, 25 ^$\circ$ C)

Question 6

Without reference to a table, arrange these reactions according to increasing $\Delta$ S.
1) CH₄(g) + H₂O(g) $\rarr$ CO(g) + 3H₂(g)
2) C(s) + O₂(g) $\rarr$ CO₂(g)
3) H₂O₂(l) $\rarr$ H₂O(l) + ¹/₂O₂(g)

A) 1 < 3 < 2
B) 2 < 3 < 1
C) 2 < 1 < 3
D) 3 < 2 < 1
E) 3 < 1 < 2

Question 7

Which response includes all the following processes that are accompanied by an increase in entropy
1) 2SO₂(g) + O₂(g) $\rarr$ SO₃(g)
2) H₂O(l) $\rarr$ H₂O(s)
3) Br₂(l) $\rarr$ Br₂(g)
4) H₂O₂(l) $\rarr$ H₂O(l) + ¹/₂O₂(g)

A) 1, 2, 3, 4
B) 1, 2
C) 2, 3, 4
D) 3, 4
E) 1, 4

Question 8

Which of these species would you expect to have the lowest standard entropy (S ^$\circ$ )

A) Br₂(l)
B) Cl₂(g)
C) F₂(g)
D) H₂(g)
E) I₂(s)

Question 9

Which response includes all of the following processes that are accompanied by an increase in entropy
1) I₂(s) $\rarr$ I₂(g)
2) 2I(g) $\rarr$ I₂(g)
3) 2NH₃(g) $\rarr$ N₂(g) + 3H₂(g)
4) Mg²⁺(aq) + 2OH^-(aq) $\rarr$ Mg(OH)₂(s)

A) 1, 2
B) 1, 3
C) 3, 4
D) 3
E) 2, 4

Question 10

Which response includes all of the following processes that are accompanied by an increase of entropy I) $\mathrm{NaCl}(\mathrm{s}) \xrightarrow{\mathrm{H}_{2} \mathrm{O}} \mathrm{Na}^{+}(\mathrm{aq})+\mathrm{Cl}^{-}(\mathrm{aq})$
II) $\mathrm{CaSO}_{4}(\mathrm{s}) \xrightarrow{\mathrm{H}_{2} \mathrm{O}} \mathrm{Ca}^{2+}(\mathrm{aq})+\mathrm{SO}_{4}{ }^{2-}(\mathrm{aq})$
III) $\mathrm{KNO}_{3}(\mathrm{s}) \xrightarrow{\mathrm{H}_{2} \mathrm{O}} \mathrm{K}^{+}(\mathrm{aq})+\mathrm{NO}_{3}^{-}(\mathrm{aq})$

A) I and III
B) II and III
C) I, II and III
D) II only
E) III only

Question 11

Sulfur can be separated from lead in the mineral galena, PbS(s), by "roasting" the ore in the presence of oxygen as shown in the following reaction: 2PbS(s) + 3O₂(g) $\rarr$ 2PbO(s) + 2SO₂(g)
Calculate $\Delta$ S ^$\circ$ for this reaction using the thermodynamic data provided below. $\begin{array}{|l|c|}\hline & \mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol}) \\\hline \mathrm{PbS}(s) & 91.2 \\\hline \mathrm{O}_{2}(g) & 205.0 \\\hline \mathrm{PbO}(s) & 69.45 \\\hline \mathrm{SO}_{2}(g) & 248.5 \\\hline\end{array}$

A) -410 J/K·mol
B) -161.5 J/K·mol
C) -47.7 J/K·mol
D) 21.8 J/K·mol
E) 43.5 J/K·mol

Question 12

Which one of the following reactions would you expect to have the lowest $\Delta$ S ^$\circ$

A) CH₄(g) + 2O₂(g) $\rarr$ CO₂(g) + 2H₂O(g)
B) C₂H₂(g) + ⁵/₂O₂(g) $\rarr$ 2CO₂(g) + H₂O(g)
C) C₂H₄(g) + O₂(g) $\rarr$ 2CO₂(g) + 2H₂O(g)
D) C₂H₆(g) + ⁷/₂O₂(g) $\rarr$ 2CO₂(g) + 3H₂O(g)

Question 13

Which of these species has the highest entropy (S ^$\circ$ ) at 25 ^$\circ$ C

A) CO(g)
B) CH₄(g)
C) NaCl(s)
D) H₂O(l)
E) Fe(s)

Question 14

Which one of the following reactions would you expect to have highest $\Delta$ S ^$\circ$

A) CH₄(g) + 2O₂(g) $\rarr$ CO₂(g) + 2H₂O(g)
B) C₂H₂(g) + ⁵/₂O₂(g) $\rarr$ 2CO₂(g) + H₂O(g)
C) C₂H₄(g) + 3O₂(g) $\rarr$ 2CO₂(g) + 2H₂O(g)
D) C₂H₆(g) + ⁷/₂O₂(g) $\rarr$ 2CO₂(g) + 3H₂O(g)

Question 15

Arrange the following substances in the order of increasing entropy at 25 ^$\circ$ C.HF(g), NaF(s), SiF₄(g), SiH₄(g), Al(s)
lowest $\rarr$ highest

A) SiF₄(g) < SiH₄(g) < NaF(s) < HF(g) < Al(s)
B) HF(g) < Al(s) < NaF(s) < SiF₄(g) < SiH₄(g)
C) Al(s) < NaF(s) < HF(g) < SiH₄(g) < SiF₄(g)
D) Al(s) < HF(g) < NaF(s) < SiF₄(g) < SiH₄(g)
E) NaF(s) < Al(s) < HF(g) < SiF₄(g) < SiH₄(g)

Question 16

Determine $\Delta$ S ^$\circ$ for the reaction SO₃(g) + H₂O(l) $\rarr$ H₂SO₄(l). $\begin{array}{lc}&\mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol})\\\hline\mathrm{SO}_{3} & 256.2 \\\mathrm{H}_{2} \mathrm{O} & 69.9 \\\mathrm{H}_{2} \mathrm{SO}_{4} & 156.9\end{array}$

A) 169.2 J/K·mol
B) 1343.2 J/K·mol
C) -169.2 J/K·mol
D) -29.4 J/K·mol
E) 29.4 J/K·mol

Question 17

Which of these species would you expect to have the lowest standard entropy (S ^$\circ$ )

A) CH₄(g)
B) HF(g)
C) NH₃(g)
D) H₂O(g)

Question 18

Arrange these compounds in order of increasing standard molar entropy at 25 ^$\circ$ C: C₃H₈(g), C₂H₄(g), ZnS(s), and H₂O(l).

A) ZnS(s) < H₂O(l) < C₃H₈(g) < C₂H₄(g)
B) C₂H₄(g) < H₂O(l) < C₃H₈(g) < NaCl(s)
C) ZnS(s) < C₃H₈(g) < C₂H₄(g) < H₂O(l)
D) C₃H₈(g) < C₂H₄(g) < H₂O(l) < ZnS(s)
E) ZnS(s) < H₂O(l) < C₂H₄(g) < C₃H₈(g)

Question 19

Which of the following is expected to have zero entropy
I. N₂(g) at 273 K
II. SiO₂(s, amorphous) at 0 K
III. NaCl(s) perfectly ordered crystal at 25 K
IV. Na(s) perfectly ordered crystal at 0 K

A) I and IV
B) III and IV
C) I and II
D) I, II, and III
E) IV only

Question 20

Arrange these reactions according to increasing $\Delta$ S.
1) H₂O(g) $\rarr$ H₂O(l)
2) 2NO(g) $\rarr$ N₂(g) + O₂(g)
3) MgCO₃(s) $\rarr$ MgO(s) + CO₂(g)

A) 1 < 2 < 3
B) 2 < 3 < 1
C) 3 < 2 < 1
D) 2 < 1 < 3
E) 1 < 3 < 2

Question 21

For the reaction H₂(g) + S(s) $\rarr$ H₂S(g), $\Delta$ H ^$\circ$ = -20.2 kJ/mol and $\Delta$ S ^$\circ$ = +43.1 J/K·mol. Which of these statements is true

A) The reaction is only spontaneous at low temperatures.
B) The reaction is spontaneous at all temperatures.
C) ( $\Delta$ G ^$\circ$ ) becomes less favorable as temperature increases.
D) The reaction is spontaneous only at high temperatures.
E) The reaction is at equilibrium at 25 ^$\circ$ C under standard conditions.

Question 22

With respect to the system only, a reaction with $\Delta$ H > 0 and $\Delta$ S < 0 is predicted to be:

A) Spontaneous at all temperatures
B) Spontaneous at high temperatures only
C) Spontaneous at low temperatures only
D) Nonspontaneous at all temperatures

Question 23

The normal freezing point of ammonia is -78 ^$\circ$ C. Predict the signs of $\Delta$ H, $\Delta$ S, and $\Delta$ G for ammonia when it freezes at -80 ^$\circ$ C and 1 atm: NH₃(l) $\rarr$ NH₃(s). $\begin{array}{llll}&\Delta \mathrm{H} & \Delta \mathrm{S} & \Delta \mathrm{G}\\\hline\text { A. } & - & - & 0 \\\text { B. } & - & + & - \\\text { C. } & + & - & + \\\text { D. } & + & + & 0 \\\text { E. } & - & - & -\end{array}$

A) A
B) B
C) C
D) D
E) E

Question 24

Which of the following is consistent with a spontaneous process in the forward direction

A)( $\Delta$ S_univ) > 0, $\Delta$ G < 0, T $\Delta$ S_univ > 0
B)( $\Delta$ S_univ) < 0, $\Delta$ G > 0, T $\Delta$ S_univ < 0
C)( $\Delta$ S_univ) > 0, $\Delta$ G < 0, T $\Delta$ S_univ < 0
D)( $\Delta$ S_univ) < 0, $\Delta$ G < 0, T $\Delta$ S_univ < 0
E)( $\Delta$ S_univ) > 0, $\Delta$ G > 0, T $\Delta$ S_univ > 0

Question 25

The element oxygen was prepared by Joseph Priestley in 1774 by heating mercury(II) oxide: HgO(s) $\rarr$ Hg(l) + ¹/₂O₂(g), $\Delta$ H ^$\circ$ = 90.84 kJ/mol.Estimate the temperature at which this reaction will become spontaneous under standard state conditions.S ^$\circ$ (Hg) = 76.02 J/K·mol
S ^$\circ$ (O₂) = 205.0 J/K·mol
S ^$\circ$ (HgO) = 70.29 J/K·mol

A) 108 K
B) 430 K
C) 620 K
D) 775 K
E) 840 K

Question 26

With respect to the system only, a reaction with $\Delta$ H < 0 and $\Delta$ S > 0 is predicted to be:

A) Spontaneous at all temperatures
B) Spontaneous at high temperatures only
C) Spontaneous at low temperatures only
D) Nonspontaneous at all temperatures

Question 27

Which of the following is consistent with a spontaneous endothermic reaction

A)( $\Delta$ H) > 0, $\Delta$ S < 0, $\Delta$ G < 0
B)( $\Delta$ H) > 0, $\Delta$ S > 0, $\Delta$ G < 0
C)( $\Delta$ H) < 0, $\Delta$ S < 0, $\Delta$ G < 0
D)( $\Delta$ H) < 0, $\Delta$ S > 0, $\Delta$ G > 0
E)( $\Delta$ H) > 0, $\Delta$ S < 0, $\Delta$ G > 0

Question 28

HI has a normal boiling point of -35.4 ^$\circ$ C, and its $\Delta$ H_vap is 21.16 kJ/mol. Calculate the molar entropy of vaporization ( $\Delta$ S_vap).

A) 598 J/K·mol
B) 68.6 J/K·mol
C) 75.2 J/K·mol
D) 0.068 J/K·mol
E) 89.0 J/K·mol

Question 29

Aluminum forms a layer of aluminum oxide when exposed to air which protects the bulk metal from further corrosion.4Al(s) + 3O₂(g) $\rarr$ 2Al₂O₃(s) Calculate $\Delta$ G ^$\circ$ for this reaction, given that $\Delta$ G ^$\circ$ _f of aluminum oxide is -1576.4 kJ/mol.

A) -3152.8 kJ/mol
B) -1576.4 kJ/mol
C) -788.2 kJ/mol
D) 1576.4 kJ/mol
E) 3152.8 kJ/mol

Question 30

The normal boiling point of acetic acid is 118.1 ^$\circ$ C. If a sample of the acetic acid is at 125.2 ^$\circ$ C, predict the signs of $\Delta$ H, $\Delta$ S, and $\Delta$ G for the boiling process at this temperature.

A) ( $\Delta$ H) > 0, $\Delta$ S > 0, $\Delta$ G < 0
B) ( $\Delta$ H) > 0, $\Delta$ S > 0, $\Delta$ G > 0
C) ( $\Delta$ H) > 0, $\Delta$ S < 0, $\Delta$ G < 0
D) ( $\Delta$ H) < 0, $\Delta$ S > 0, $\Delta$ G > 0
E) ( $\Delta$ H) < 0, $\Delta$ S < 0, $\Delta$ G > 0

Question 31

Which of the following is consistent with an exothermic reaction that is nonspontaneous at high temperatures

A)( $\Delta$ H) > 0, $\Delta$ S < 0, $\Delta$ G < 0
B)( $\Delta$ H) > 0, $\Delta$ S > 0, $\Delta$ G < 0
C)( $\Delta$ H) < 0, $\Delta$ S > 0, $\Delta$ G < 0
D)( $\Delta$ H) < 0, $\Delta$ S > 0, $\Delta$ G > 0
E)( $\Delta$ H) < 0, $\Delta$ S < 0, $\Delta$ G > 0

Question 32

Calculate $\Delta$ S ^$\circ$ at 25 ^$\circ$ C for the reduction of PbO(s), 2PbO(s) + C(s) $\rarr$ 2Pb(s) + CO₂(g) given these absolute entropies: $\begin{array}{lc}&\mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol})\\\hline\mathrm{PbO}(\mathrm{s}) & 69.45 \\\mathrm{C}(\mathrm{s}) & 5.7 \\\mathrm{Pb}(\mathrm{s}) & 64.89 \\\mathrm{CO}_{2}(\mathrm{g}) & 213.6\end{array}$

A) +198.8 J/K·mol
B) +488.0 J/K·mol
C) +353.6 J/K·mol
D) -203.3 J/K·mol
E) +203.3 J/K·mol

Question 33

Sodium carbonate can be made by heating sodium bicarbonate: 2NaHCO₃(s) $\rarr$ Na₂CO₃(s) + CO₂(g) + H₂O(g)
Given that $\Delta$ H ^$\circ$ = 128.9 kJ/mol and $\Delta$ G ^$\circ$ = 33.1 kJ/mol at 25 ^$\circ$ C, above what minimum temperature will the reaction become spontaneous under standard state conditions

A) 0.4 K
B) 3.9 K
C) 321 K
D) 401 K
E) 525 K

Question 34

Which of the following is consistent with an exothermic reaction that is spontaneous at all temperatures

A)( $\Delta$ H) > 0, $\Delta$ S < 0, $\Delta$ G < 0
B)( $\Delta$ H) > 0, $\Delta$ S > 0, $\Delta$ G < 0
C)( $\Delta$ H) < 0, $\Delta$ S < 0, $\Delta$ G < 0
D)( $\Delta$ H) < 0, $\Delta$ S > 0, $\Delta$ G < 0
E)( $\Delta$ H) > 0, $\Delta$ S < 0, $\Delta$ G > 0

Question 35

Which of the following is consistent with a nonspontaneous process in the forward direction

A)( $\Delta$ S_univ) > 0, $\Delta$ G < 0, T $\Delta$ S_univ > 0
B)( $\Delta$ S_univ) < 0, $\Delta$ G > 0, T $\Delta$ S_univ < 0
C)( $\Delta$ S_univ) > 0, $\Delta$ G < 0, T $\Delta$ S_univ < 0
D)( $\Delta$ S_univ) < 0, $\Delta$ G < 0, T $\Delta$ S_univ < 0
E)( $\Delta$ S_univ) > 0, $\Delta$ G > 0, T $\Delta$ S_univ > 0

Question 36

Ozone (O₃) in the atmosphere can react with nitric oxide (NO): O₃(g) + NO(g) $\rarr$ NO₂(g) + O₂(g).Calculate the $\Delta$ G ^$\circ$ for this reaction at 25 ^$\circ$ C. ( $\Delta$ H ^$\circ$ = -199 kJ/mol, $\Delta$ S ^$\circ$ = -4.1 J/K·mol)

A) 1020 kJ/mol
B) -1.22 * 10³ kJ/mol
C) 2.00 * 10³ kJ/mol
D) -1.42 * 10³ kJ/mol
E) -198 kJ/mol

Question 37

The normal melting point of sulfur is 113 ^$\circ$ C. If a sample of solid sulfur is at 95 ^$\circ$ C, predict the signs of $\Delta$ H, $\Delta$ S, and $\Delta$ G for the melting process at this temperature.

A) ( $\Delta$ H) > 0, $\Delta$ S > 0, $\Delta$ G < 0
B) ( $\Delta$ H) > 0, $\Delta$ S > 0, $\Delta$ G > 0
C) ( $\Delta$ H) > 0, $\Delta$ S < 0, $\Delta$ G < 0
D) ( $\Delta$ H) < 0, $\Delta$ S > 0, $\Delta$ G > 0
E) ( $\Delta$ H) < 0, $\Delta$ S < 0, $\Delta$ G > 0

Question 38

Calculate $\Delta$ G ^$\circ$ for the reaction 3NO₂(g) + H₂O(l) $\rarr$ 2HNO₃(l) + NO(g). $\begin{array}{lc}&\Delta \mathrm{G}^{\circ}_\mathrm{f}(\mathrm{~kJ} / \mathrm{mol})\\\hline\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) & -237.2 \\\mathrm{HNO}_{3}(\mathrm{l}) & -79.9 \\\mathrm{NO}{(\mathrm{g}}) & 86.7 \\\mathrm{NO}_{2}(\mathrm{g}) & 51.8\end{array}$

A) 8.7 kJ/mol
B) 192 kJ/mol
C) -414 kJ/mol
D) -192 kJ/mol
E) -155 kJ/mol

Question 39

Calculate $\Delta$ S ^$\circ$ for the reaction SO₂(s) + NO₂(g) $\rarr$ SO₃(g) + NO(g). $\begin{array}{lc}&\mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol})\\\hline\mathrm{SO}_{2}(\mathrm{g}) & 248.5 \\\mathrm{SO}_{3}(\mathrm{g}) & 256.2 \\\mathrm{NO}{(g)} & 210.6 \\\mathrm{NO}_{2}(\mathrm{g}) & 240.5\end{array}$

A) 53.6 J/K·mol
B) -53.6 J/K·mol
C) -22.2 J/K·mol
D) 474.8 J/K·mol
E) -474.8 J/K·mol

Question 40

Hydrogen peroxide (H₂O₂) decomposes according to the equation H₂O₂(l) $\rarr$ H₂O(l) + ¹/₂O₂(g).Calculate K_p for this reaction at 25 ^$\circ$ C. $\Delta$ H ^$\circ$ = -98.2 kJ/mol, $\Delta$ S ^$\circ$ = 70.1 J/K·mol)

A) 1.3 * 10^-21
B) 20.9
C) 3.46 * 10¹⁷
D) 7.5 * 10²⁰
E) 8.6 * 10⁴

Question 41

Calculate the equilibrium constant for the decomposition of water 2H₂O(l) $\leftrightharpoons$ 2H₂(g) + O₂(g)
At 25 ^$\circ$ C, given that $\Delta$ G ^$\circ$ _f (H₂O(l)) = -237.2 kJ/mol.

A) 0.83
B) 6.3 * 10^-84
C) 2.5 * 10^-42
D) 1.6 * 10⁸³
E) 4.7 * 10⁵

Question 42

Which of the following is consistent with a reaction that proceeds spontaneously in the forward direction

A) ( $\Delta$ G) > 0, Q < K
B) ( $\Delta$ G ^$\circ$ ) = 0, Q = K
C) ( $\Delta$ G) < 0, Q > K
D) ( $\Delta$ G ^$\circ$ ) > 0, Q = K
E) ( $\Delta$ G) < 0, Q < K

Question 43

At 1500 ^$\circ$ C the equilibrium constant for the reaction CO(g) + 2H₂(g) $\leftrightharpoons$ CH₃OH(g) has the value K_p = 1.4 * 10^-7. Calculate $\Delta$ G ^$\circ$ for this reaction at 1500 ^$\circ$ C.

A) 105 kJ/mol
B) 1.07 kJ/mol
C) -233 kJ/mol
D) -105 kJ/mol
E) 233 kJ/mol

Question 44

The equilibrium constant for the reaction AgBr(s) $\leftrightharpoons$ Ag⁺(aq) + Br^- (aq) is the solubility product constant, K_sp = 7.7 *10^-13 at 25 ^$\circ$ C. Calculate $\Delta$ G for the reaction when [Ag⁺] = 1.0 * 10^-2 M and [Br^-] = 1.0 * 10^-3 M. Is the reaction spontaneous or nonspontaneous at these concentrations

A) ( $\Delta$ G) = 69.1 kJ/mol, nonspontaneous
B) ( $\Delta$ G) = -69.1 kJ/mol, spontaneous
C) ( $\Delta$ G) = 97.5 kJ/mol, spontaneous
D) ( $\Delta$ G) = 40.6 kJ/mol, nonspontaneous
E) ( $\Delta$ G) = -97.5 kJ/mol, nonspontaneous

Question 45

The equilibrium constant at 427 ^$\circ$ C for the reaction N₂(g) + 3H₂(g) $\leftrightharpoons$ 2NH₃(g) is K_p = 9.4 * 10^-5. Calculate the value of $\Delta$ G ^$\circ$ for the reaction under these conditions.

A) -33 kJ/mol
B) -54 kJ/mol
C) 54 kJ/mol
D) 33 kJ/mol
E) 1.3 J/mol

Question 46

Determine the equilibrium constant (K_p) at 25 ^$\circ$ C for the reaction $\begin{array}{ll}\begin{array}{l}\mathrm{CO}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \leftrightharpoons \mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g}) .\end{array}\\\\\Delta \mathrm{G}^{\circ}=-28.5 \mathrm{~kJ} / \mathrm{mol}\end{array}$

A) 2.9 * 10^-60
B) 1.0* 10^-4
C) 1.2
D) 1.0 * 10⁵
E) 3.4 * 10⁵⁹

Question 47

Calculate $\Delta$ G ^$\circ$ for the combustion of ethanol vapor, C₂H₅OH(g), at 750 ^$\circ$ C in oxygen to form carbon dioxide and water vapor. The following data is valid at 25 ^$\circ$ C: $\begin{array}{lcc}&\Delta \mathrm{H}_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol}) & \Delta \mathrm{G}_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol})\\\hline\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{~g}) & -234.8 & -167.9 \\\mathrm{O}_{2}(\mathrm{g}) & 0 & 0 \\\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) & -241.8 & -228.6 \\\mathrm{CO}_{2}(\mathrm{g}) & -393.5 & -394.4\end{array}$

A) -1407 kJ/mol
B) -2151 kJ/mol
C) -1307 kJ/mol
D) -4486 kJ/mol
E) -1377 kJ/mol

Question 48

For the reaction 2C(graphite) + H₂(g) $\rarr$ C₂H₂(g), $\Delta$ G ^$\circ$ = +209.2 kJ/mol at 25 ^$\circ$ C. If P(H₂) = 100. atm, and P(C₂H₂) = 0.10 atm, calculate $\Delta$ G for this reaction.

A) +207.8 kJ/mol
B) +226.3 kJ/mol
C) +192.1 kJ/mol
D) +17.3 kJ/mol
E) -16.9 kJ/mol

Question 49

Nitrosyl chloride (NOCl) decomposes at elevated temperatures according to the equation 2NOCl(g) $\leftrightharpoons$ 2NO(g) + Cl₂(g). Calculate K_p for this reaction at 227 ^$\circ$ C. ( $\Delta$ H ^$\circ$ = 81.2 kJ/mol, $\Delta$ S ^$\circ$ = 128 J/K·mol)

A) 1.59 * 10^-2
B) 2.10 * 10^-7
C) 62.8
D) 4.90 * 10⁶
E) 3.20 * 10⁹

Question 50

For the reaction 2NO(g) + O₂(g) $\rarr$ 2NO₂(g) if initially P(NO) = 1.5 atm, P(O₂) = 1.4 atm, and P(NO₂) = 2.0 atm, calculate $\Delta$ G for this reaction at 25 ^$\circ$ C. The following data is valid at 25 ^$\circ$ C: $\begin{array}{|c|c|}\hline & \Delta \mathrm{G}_{\mathrm{f}}{ }^{\circ}(\mathrm{kJ} / \mathrm{mol}) \\\hline \mathrm{NO} & 86.7 \\\hline \mathrm{NO}_{2} & 51.8 \\\hline\end{array}$

A) -69.9 kJ/mol
B) -69.2 kJ/mol
C) 522.1 kJ/mol
D) -79.9 kJ/mol
E) -35.0 kJ/mol

Question 51

Determine the equilibrium constant K_p at 25 ^$\circ$ C for the reaction N₂(g) + 3H₂(g) $\leftrightharpoons$ 2NH₃(g).[ $\Delta$ G ^$\circ$ _f (NH₃(g)) = -16.6 kJ/mol]

A) 1.52 * 10^-6
B) 6.60 * 10⁵
C) 8.28 * 10^-2
D) 2.60
E) 13.4

Question 52

Find the temperature at which the reaction N₂O₄(g) $\leftrightharpoons$ 2NO₂(g) will be in equilibrium when both gases are present at partial pressures of 1.00 atm. $\begin{array}{lcc}&\Delta \mathrm{H}^{\circ}{ }_{\mathrm{f}}\left(25^{\circ} \mathrm{C}\right) & \Delta \mathrm{G}^{\circ}_\mathrm{f}\left(25^{\circ} \mathrm{C}\right)\\\hline\mathrm{NO}_{2}(\mathrm{g}) & 33.85 \mathrm{~kJ} / \mathrm{mol} & 51.8 \mathrm{~kJ} / \mathrm{mol} \\\mathrm{N}_{2} \mathrm{O}_{4}(\mathrm{g}) & 9.66 \mathrm{~kJ} / \mathrm{mol} & 98.29 \mathrm{~kJ} / \mathrm{mol}\end{array}$

A) 300 ^$\circ$ C
B) 28 ^$\circ$ C
C) 55 ^$\circ$ C
D) 32 ^$\circ$ C
E) 562 ^$\circ$ C

Question 53

K_w for the auto-ionization of water, H₂O(l) $\rarr$ H⁺(aq) + OH^- (aq), is 1.0 * 10^-14. What are the signs (+/-) of $\Delta$ S ^$\circ$ and $\Delta$ H ^$\circ$ for the reaction at 25 ^$\circ$ C

A) ( $\Delta$ S ^$\circ$ ) = (+) and $\Delta$ H ^$\circ$ = (+)
B) ( $\Delta$ S ^$\circ$ ) = (+) and $\Delta$ H ^$\circ$ = (-)
C) ( $\Delta$ S ^$\circ$ ) = (-) and $\Delta$ H ^$\circ$ = (+)
D) ( $\Delta$ S ^$\circ$ ) = (-) and $\Delta$ H ^$\circ$ = (-)

Question 54

Which of the following is consistent with a reaction at equilibrium

A) ( $\Delta$ G) = 0, Q = K
B) ( $\Delta$ G ^$\circ$ ) = 0, Q > K
C) ( $\Delta$ G) > 0, Q = K
D) ( $\Delta$ G) < 0, Q = K
E) ( $\Delta$ G ^$\circ$ ) = 0, Q < K

Question 55

Which of the following is consistent with a reaction that proceeds spontaneously in the reverse direction (assume all variables are in terms of the forward direction only)

A) ( $\Delta$ G) > 0, Q < K
B) ( $\Delta$ G ^$\circ$ ) = 0, Q = K
C) ( $\Delta$ G) < 0, Q > K
D) ( $\Delta$ G ^$\circ$ ) > 0, Q = K
E) ( $\Delta$ G) > 0, Q > K

Question 56

The reaction rates of many spontaneous reactions are actually very slow. Which of these statements is the best explanation for this observation

A) (K_p) for the reaction is less than one.
B) The activation energy of the reaction is large.
C) ( $\Delta$ G ^$\circ$ ) for the reaction is positive.
D) Such reactions are endothermic.
E) The entropy change is negative.

Question 57

The solubility product constant at 25 ^$\circ$ C for AgI(s) in water has the value 8.3 * 10^-17. Calculate $\Delta$ G_rxn at 25 ^$\circ$ C for the process AgI(s) $\leftrightharpoons$ Ag⁺(aq) + I^- (aq) where [Ag⁺] = 9.1 * 10^-9 and [I^-] = 9.1 * 10^-9.

A) +4.4 kJ/mol
B) +91.7 kJ/mol
C) 0.0 kJ/mol
D) -91.7 kJ/mol
E) -4.4 kJ/mol

Question 58

Calculate K_p at 298 K for the reaction SO₂(g) + NO₂(g) $\leftrightharpoons$ SO₃(g) + NO(g). $\begin{array}{lc}&\Delta \mathrm{G}_{\mathrm{f}}^{\circ}\\\hline\mathrm{SO}_{2}(\mathrm{g}) & -300.4 \mathrm{~kJ} / \mathrm{mol} \\\mathrm{SO}_{3}(\mathrm{g}) & -370.4 \mathrm{~kJ} / \mathrm{mol} \\\mathrm{NO}(\mathrm{g}) & 86.7 \mathrm{~kJ} / \mathrm{mol} \\\mathrm{NO}_{2}(\mathrm{g}) & 51.8 \mathrm{~kJ} / \mathrm{mol}\end{array}$

A) 6.99 * 10^-7
B) 5.71 * 10^-8
C) 14.2
D) 475
E) 1.42 * 10⁶

Question 59

For the reaction 2 SO₂(g) + O₂(g) $\rarr$ 2 SO₃(g), if initially P(SO₂) = 1.2 atm, P(O₂) = 1.8 atm, and P(SO₃) = 2.1 atm, calculate $\Delta$ G for this reaction at 25 ^$\circ$ C. The following data is valid at 25 ^$\circ$ C: $\begin{array}{|l|l|}\hline & \Delta \mathrm{G}_{\mathrm{f}}{ }^{\circ}(\mathrm{kJ} / \mathrm{mol}) \\\hline \mathrm{SO}_{2} & -300.4 \\\hline \mathrm{SO}_{3} & -370.4 \\\hline\end{array}$

A) -140.0 kJ/mol
B) -137.6 kJ/mol
C) -138.7 kJ/mol
D) 1,174.7 kJ/mol
E) -141.3 kJ/mol

Question 60

Predict the normal boiling point of triethylborane (C₆H₁₅B) using the following data: $\begin{array}{lcc}&\Delta \mathrm{H}^{\circ}{ }_{\mathrm{f}}\left(25^{\circ} \mathrm{C}\right) & \Delta \mathrm{G}^{\circ}_\mathrm{f}\left(25^{\circ} \mathrm{C}\right)\\\hline\mathrm{C}_{6} \mathrm{H}_{15} \mathrm{~B}(\mathrm{l}) & -194.6 \mathrm{~kJ} / \mathrm{mol} & 9.4 \mathrm{~kJ} / \mathrm{mol} \\\mathrm{C}_{6} \mathrm{H}_{15} \mathrm{~B}(\mathrm{g}) & -157.7 \mathrm{~kJ} / \mathrm{mol} & 16.1 \mathrm{~kJ} / \mathrm{mol}\end{array}$

A) 92 ^$\circ$ C
B) -21 ^$\circ$ C
C) 21 ^$\circ$ C
D) 365 ^$\circ$ C
E) 256 ^$\circ$ C

Question 61

In the gas phase, formic acid forms a dimer, 2HCOOH(g) $\leftrightharpoons$ (HCOOH)₂(g). For this reaction, $\Delta$ H ^$\circ$ = -60.1 kJ/mol and $\Delta$ G ^$\circ$ = -13.9 kJ/mol at 25 ^$\circ$ C. Find the equilibrium constant (K_p) for this reaction at 75 ^$\circ$ C.

A) 8960
B) 273
C) 0.120
D) 8.33
E) 1.12 * 10^-4

Question 62

The standard free energy of formation of gaseous hydrogen iodide is 1.30 kJ/mol at 25 ^$\circ$ C. Find K_p for the reaction H₂(g) + I₂(s) $\leftrightharpoons$ 2HI(g) at this temperature.

A) 7.0
B) 7100
C) 1.0
D) 2.4
E) 2.9

Question 63

Using the thermodynamic data provided below, calculate the standard change in entropy when one mole of sodium sulfate is dissolved in water. $\begin{array}{|l|c|}\hline & \mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol}) \\\hline \mathrm{Na}_{2} \mathrm{SO}_{4}(s) & 149.49 \\\hline \mathrm{Na}^{+}(a q) & 60.25 \\\hline \mathrm{SO}_{4}{ }^{2-}(a q) & 17.15 \\\hline\end{array}$ Will the solubility of sodium nitrate increase or decrease if the temperature of the system is increased

A) -11.84 J/K·mol; solubility decreases with increasing temperature
B) -11.84 J/K·mol; solubility increases with increasing temperature
C) 11.84 J/K·mol; solubility decreases with increasing temperature
D) 11.84 J/K·mol; solubility increases with increasing temperature
E) None of the above

Question 64

For the reaction CuS(s) + H₂(g) $\leftrightharpoons$ H₂S(g) + Cu(s),
$\Delta$ G ^$\circ$ _f (CuS) = -53.6 kJ/mol
$\Delta$ G ^$\circ$ _f (H₂S) = -33.6 kJ/mol
$\Delta$ H ^$\circ$ _f (CuS) = -53.1 kJ/mol
$\Delta$ H ^$\circ$ _f (H₂S) = -20.6 kJ/mol
Calculate the value of the equilibrium constant (K_p) at 798 K and 1 atm pressure.

A) 1.77
B) 1.57
C) 1.37
D) 1.17
E) None of the above

Question 65

A sample of solid naphthalene is introduced into an evacuated flask. Use the data below to calculate the equilibrium vapor pressure of naphthalene (C₁₀H₈) in the flask at 35 ^$\circ$ C. $\begin{array}{lcc}&\Delta \mathrm{H}^{\circ}{ }_{\mathrm{f}}\left(25^{\circ} \mathrm{C}\right) & \Delta \mathrm{G}^{\circ}_\mathrm{f}\left(25^{\circ} \mathrm{C}\right)\\\hline\mathrm{C}_{10} \mathrm{H}_{8}(\mathrm{s}) & 78.5 \mathrm{~kJ} / \mathrm{mol} & 201.6 \mathrm{~kJ} / \mathrm{mol} \\\mathrm{C}_{10} \mathrm{H}_{8}(\mathrm{g}) & 150.6 \mathrm{~kJ} / \mathrm{mol} & 224.1 \mathrm{~kJ} / \mathrm{mol}\end{array}$

A) 890. mmHg
B) 0.21 mmHg
C) 696 mmHg
D) 0.086 mmHg
E) 833 mmHg

Question 66

For the reaction HCONH₂(g) $\leftrightharpoons$ NH₃(g) + CO(g), K_c = 4.84 at 400 K. If $\Delta$ H ^$\circ$ for this reaction is 29 kJ/mol, find K_c at 500 K.

A) 5.8
B) 0.17
C) 27
D) 0.88
E) 10.3

Question 67

Using the thermodynamic data provided below, calculate the standard change in entropy when one mole of sodium nitrate is dissolved in water. $\begin{array}{|l|c|}\hline & \mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol}) \\\hline \mathrm{NaNO}_{3}(\mathrm{s}) & 116.3 \\\hline \mathrm{Na}^{+}(a q) & 60.25 \\\hline \mathrm{NO}_{3}^{-}(a q) & 146.4 \\\hline\end{array}$ Will the solubility of sodium nitrate increase or decrease if the temperature of the system is increased

A) -90.4 J/K·mol; solubility decreases with increasing temperature
B) -90.4 J/K·mol; solubility increases with increasing temperature
C) 90.4 J/K·mol; solubility decreases with increasing temperature
D) 90.4 J/K·mol; solubility increases with increasing temperature
E) None of the above

Question 68

For the reaction SbCl₅(g) $\leftrightharpoons$ SbCl₃(g) + Cl₂(g),
$\Delta$ G ^$\circ$ _f (SbCl₅) = -334.34 kJ/mol
$\Delta$ G ^$\circ$ _f (SbCl₃) = -301.25 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₅) = -394.34 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₃) = -313.80 kJ/mol
Calculate the value of the equilibrium constant (K_p) at 800 K and 1 atm pressure.

A) 1.31 * 10³
B) 1.11 * 10³
C) 1.91 * 10²
D) 1.71 * 10²
E) None of the above

Question 69

For the reaction CuS(s) + H₂(g) $\leftrightharpoons$ H₂S(g) + Cu(s),
$\Delta$ G ^$\circ$ _f (CuS) = -53.6 kJ/mol
$\Delta$ G ^$\circ$ _f (H₂S) = -33.6 kJ/mol
$\Delta$ H ^$\circ$ _f (CuS) = -53.1 kJ/mol
$\Delta$ H ^$\circ$ _f (H₂S) = - 20.6 kJ/mol
This reaction proceeds spontaneously at 298 K and 1 atm pressure.

Question 70

For the reaction SbCl₅(g) $\leftrightharpoons$ SbCl₃(g) + Cl₂(g),
$\Delta$ G ^$\circ$ _f (SbCl₅) = -334.34 kJ/mol
$\Delta$ G ^$\circ$ _f (SbCl₃) = -301.25 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₅) = -394.34 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₃) = -313.80 kJ/mol
Calculate $\Delta$ G at 800 K and 1 atm pressure (assume $\Delta$ S ^$\circ$ and $\Delta$ H ^$\circ$ do not change with temperature).

A) -36.66 kJ/mol
B) -46.66 kJ/mol
C) -56.66 kJ/mol
D) -66.66 kJ/mol
E) None of the above

Question 71

Rubidium has a heat of vaporization of 69.0 kJ/mol at its boiling point (686 ^$\circ$ C). Calculate $\Delta$ S for this process, Rb(l) $\rarr$ Rb(g), at 1 atm and 686 ^$\circ$ C.

A) 65.9 J/K·mol
B) 67.9 J/K·mol
C) 69.9 J/K·mol
D) 71.9 J/K·mol
E) None of the above

Question 72

For the reaction CuS(s) + H₂(g) $\leftrightharpoons$ H₂S(g) + Cu(s),
$\Delta$ G ^$\circ$ _f (CuS) = -53.6 kJ/mol
$\Delta$ G ^$\circ$ _f (H₂S) = -33.6 kJ/mol
$\Delta$ H ^$\circ$ _f (CuS) = -53.1 kJ/mol
$\Delta$ H ^$\circ$ _f (H₂S) = - 20.6 kJ/mol
Calculate the value of the equilibrium constant (K_p) for this reaction at 298 K.

A) 2.71 * 10^-4
B) 2.91 * 10^-4
C) 3.11 * 10^-4
D) 3.31 * 10^-4
E) None of the above

Question 73

For the reaction SbCl₅(g) $\leftrightharpoons$ SbCl₃(g) + Cl₂(g),
$\Delta$ G ^$\circ$ _f (SbCl₅) = -334.34 kJ/mol
$\Delta$ G ^$\circ$ _f (SbCl₃) = -301.25 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₅) = -394.34 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₃) = -313.80 kJ/mol
This reaction proceeds spontaneously at 298 K and 1 atm pressure.

Question 74

The free energy of formation of nitric oxide, NO, at 1000 K (roughly the temperature in an automobile engine during ignition) is about 78 kJ/mol. Calculate the equilibrium constant K_p for the reaction N₂(g) + O₂(g) $\leftrightharpoons$ 2NO(g) at this temperature.

A) K_p = 6.9 * 10^-9
B) K_p = 7.1 *10^-9
C) K_p = 7.3 * 10^-9
D) K_p = 7.5 * 10^-9
E) None of the above

Question 75

Find the temperature at which K_p = 42.0 for the reaction H₂(g) + I₂(g) $\leftrightharpoons$ 2HI(g). [Given: at 25 ^$\circ$ C, for H₂(g), $\Delta$ H ^$\circ$ _f = 0, S ^$\circ$ = 131.0 J/mol·K; for I₂(g), $\Delta$ H ^$\circ$ _f = 62.26 kJ/mol, S ^$\circ$ = 260.6 J/mol·K; for HI(g), $\Delta$ H ^$\circ$ _f = 25.9 kJ/mol, S ^$\circ$ = 206.3 J/mol·K; assume that $\Delta$ H ^$\circ$ and $\Delta$ S ^$\circ$ are independent of temperature.]

A) 1040 K
B) 168 K
C) 539 K
D) 1400 K
E) 34,200 K

Question 76

Assuming $\Delta$ S ^$\circ$ and $\Delta$ H ^$\circ$ do not vary with temperature, at what temperature will the reaction shown below become spontaneous
C(s) + H₂O(g) $\rarr$ H₂(g) + CO(s) ( $\Delta$ S ^$\circ$ = 133.6 J/K·mol; $\Delta$ H ^$\circ$ = 131.3 kJ/mol)

A) 670 ^$\circ$ C
B) 690 ^$\circ$ C
C) 710 ^$\circ$ C
D) 730 ^$\circ$ C
E) None of the above

Question 77

For the reaction SbCl₅(g) $\leftrightharpoons$ SbCl₃(g) + Cl₂(g),
$\Delta$ G ^$\circ$ _f (SbCl₅) = -334.34 kJ/mol
$\Delta$ G ^$\circ$ _f (SbCl₃) = -301.25 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₅) = -394.34 kJ/mol
$\Delta$ H ^$\circ$ _f (SbCl₃) = -313.80 kJ/mol
Calculate the value of the equilibrium constant (K_p) for this reaction at 298 K.

A) 1.38 * 10^-6
B) 1.58 * 10^-6
C) 1.78 * 10^-6
D) 1.98 * 10^-6
E) None of the above

Question 78

In the gas phase, methyl isocyanate (CH₃NC) isomerizes to acetonitrile (CH₃CN), H₃C-N $\equiv$ C (g) $\leftrightharpoons$ H₃C-C $\equiv$ N (g)
With $\Delta$ H ^$\circ$ = -89.5 kJ/mol and $\Delta$ G ^$\circ$ = - 73.8 kJ/mol at 25 ^$\circ$ C. Find the equilibrium constant for this reaction at 100 ^$\circ$ C.

A) 1.68 * 10^-10
B) 5.96 * 10⁹
C) 2.16 * 10¹⁰
D) 4.63 * 10^-11
E) 8.64 * 10¹²

Question 79

Find the temperature at which K_p = 4.00 for the reaction N₂O₄(g) $\leftrightharpoons$ 2NO₂(g). [Given: at 25 ^$\circ$ C, for NO₂(g), $\Delta$ H ^$\circ$ _f = 33.85 kJ/mol, S ^$\circ$ = 240.46 J/mol·K; for N₂O₄(g), $\Delta$ H ^$\circ$ _f = 9.66 kJ/mol, S ^$\circ$ = 304.3 J/mol·K; assume that $\Delta$ H ^$\circ$ and $\Delta$ S ^$\circ$ are independent of temperature.]

A) 197 ^$\circ$ C
B) 56 ^$\circ$ C
C) 36 ^$\circ$ C
D) 79 ^$\circ$ C
E) 476 ^$\circ$ C

Question 80

For the reaction CuS(s) + H₂(g) $\leftrightharpoons$ H₂S(g) + Cu(s),
$\Delta$ G ^$\circ$ _f (CuS) = -53.6 kJ/mol
$\Delta$ G ^$\circ$ _f (H₂S) = -33.6 kJ/mol
$\Delta$ H ^$\circ$ _f (CuS) = -53.1 kJ/mol
$\Delta$ H ^$\circ$ _f (H₂S) = -20.6 kJ/mol
Calculate $\Delta$ G at 798 K and 1 atm pressure (assume $\Delta$ S ^$\circ$ and $\Delta$ H ^$\circ$ do not change with temperature).

A) -1.02 kJ/mol
B) -1.22 kJ/mol
C) -1.42 kJ/mol
D) -1.62 kJ/mol
E) None of the above