Question 1

Predict the signs (-, +, or 0)  of  Δ\DeltaΔ H and  Δ\DeltaΔ S, in that order, for the reaction: O2(g)   →\rarr→  2O(g) .

Accepted Answer

A)   +,-
B)   -, +
C)   +, +
D)   -, -
E)   None of the above F) A) and C)
G) None of the above

Question 2

The heat of vaporization of water is 2.27 kJ/g. What is  Δ\DeltaΔ Svap per mole at the normal boiling point

Accepted Answer

A)   170. J/K·mol
B)   150. J/K·mol
C)   130. J/K·mol
D)   110. J/K·mol
E)   None of the above F) C) and D)
G) B) and E)

Question 3

The element oxygen was prepared by Joseph Priestley in 1774 by heating mercury(II)  oxide: HgO(s)   →\rarr→  Hg(l)  + 1/2O2(g) ,  Δ\DeltaΔ 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

Accepted Answer

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

Question 4

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.

Accepted Answer

A) True 
 B)False

Question 5

Determine the equilibrium constant (Kp)  at 25 ∘\circ∘ C for the reaction  CO(g) +H2O(g) ⇋CO2(g) +H2(g) .ΔG∘=−28.5 kJ/mol\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}CO(g) +H2​O(g) ⇋CO2​(g) +H2​(g) .​ΔG∘=−28.5 kJ/mol​

Accepted Answer

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

Question 6

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

Accepted Answer

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

Question 7

Aluminum forms a layer of aluminum oxide when exposed to air which protects the bulk metal from further corrosion.4Al(s)  + 3O2(g)   →arr→  2Al2O3(s)  Using the thermodynamic data provided below, calculate  Δ\DeltaΔ S ∘\circ∘  for this reaction.  S∘(J/K⋅ mol) Al(s) 28.3O2(g) 205.0Al2O3(s) 50.99\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}Al(s) O2​(g) Al2​O3​(s) ​S∘(J/K⋅ mol) 28.3205.050.99​​

Accepted Answer

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 F) B) and C)
G) A) and B)

Question 8

Using the thermodynamic data provided below, calculate Ka1 for H2CO3(aq)  at 25 ∘\circ∘ .  ΔHf∘(kJ/mol) S∘(J/K⋅ mol) H+(aq) 00H2CO3(aq) −698.7191HCO3−(aq) −691.1195.0CO32−(aq) −676.26−53.1\begin{array}{|l|l|c|}\hline & \Delta \mathrm{H}_{\mathrm{f}}^{\circ}(\mathrm{kJ} / \mathrm{mol})  & \mathrm{S}^{\circ}(\mathrm{J} / \mathrm{K} \cdot \mathrm{~mol})  \\hline \mathrm{H}^{+}(a q)  & 0 & 0 \\hline \mathrm{H}_{2} \mathrm{CO}_{3}(a q)  & -698.7 & 191 \\hline \mathrm{HCO}_{3}^{-}(a q)  & -691.11 & 95.0 \\hline \mathrm{CO}_{3}^{2-}(a q)  & -676.26 & -53.1 \\hline\end{array}H+(aq) H2​CO3​(aq) HCO3−​(aq) CO32−​(aq) ​ΔHf∘​(kJ/mol) 0−698.7−691.11−676.26​S∘(J/K⋅ mol) 019195.0−53.1​​

Accepted Answer

A)   5 * 10-5
B)   5 * 10-6
C)   5 * 10-7
D)   5 * 10-8
E)   None of the above F) B) and D)
G) B) and C)

Question 9

Determine the equilibrium constant Kp at 25 ∘\circ∘ C for the reaction N2(g)  + 3H2(g)   ⇋\leftrightharpoons⇋  2NH3(g) .[ Δ\DeltaΔ G ∘\circ∘ f (NH3(g) )  = -16.6 kJ/mol]

Accepted Answer

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

Question 10

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.  ΔH∘f(25∘C) ΔGf∘(25∘C) C10H8(s) 78.5 kJ/mol201.6 kJ/molC10H8(g) 150.6 kJ/mol224.1 kJ/mol\begin{array}{lcc}&\Delta \mathrm{H}^{\circ}{ }_{\mathrm{f}}\left(25^{\circ} \mathrm{C}ight)  & \Delta \mathrm{G}^{\circ}_\mathrm{f}\left(25^{\circ} \mathrm{C}ight) \\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}C10​H8​(s) C10​H8​(g) ​ΔH∘f​(25∘C) 78.5 kJ/mol150.6 kJ/mol​ΔGf∘​(25∘C) 201.6 kJ/mol224.1 kJ/mol​​

Accepted Answer

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

Question 11

Predict the signs (-, +, or 0)  of  Δ\DeltaΔ H and  Δ\DeltaΔ S, in that order, for the reaction: 6CO2(g)  + 6H2O(g)   →\rarr→ C6H12O6(g)  + 6O2(g) .

Accepted Answer

A)   +, -
B)   0, +
C)   +, +
D)   -, -
E)   None of the above F) A) and C)
G) B) and D)

Question 12

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

Accepted Answer

A)   The reaction is only spontaneous at low temperatures.
B)   The reaction is spontaneous at all temperatures.
C)   ( Δ\DeltaΔ 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. F) C) and D)
G) All of the above

Question 13

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

Accepted Answer

A)  ( Δ\DeltaΔ Suniv)  > 0,  Δ\DeltaΔ G Δ\DeltaΔ Suniv > 0
B)  ( Δ\DeltaΔ Suniv)  Δ\DeltaΔ G > 0, T Δ\DeltaΔ Suniv 
C)  ( Δ\DeltaΔ Suniv)  > 0,  Δ\DeltaΔ G Δ\DeltaΔ Suniv 
D)  ( Δ\DeltaΔ Suniv)  Δ\DeltaΔ G Δ\DeltaΔ Suniv 
E)  ( Δ\DeltaΔ Suniv)  > 0,  Δ\DeltaΔ G > 0, T Δ\DeltaΔ Suniv > 0 F) A) and B)
G) A) and D)

Question 14

For any pure substance, if $\Delta$Hf$\circ$ = 0 and $\Delta$Gf$\circ$ = 0, then S$\circ$ = 0.

Accepted Answer

A) True 
 B)False

Question 15

At a given temperature, Br2(l) has a higher entropy per mole than Br2(g).

Accepted Answer

A) True 
 B)False

Question 16

Assuming  Δ\DeltaΔ S ∘\circ∘  and  Δ\DeltaΔ 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)  ( Δ\DeltaΔ S ∘\circ∘  = 133.6 J/K·mol;  Δ\DeltaΔ H ∘\circ∘  = 131.3 kJ/mol)

Accepted Answer

A)   670 ∘\circ∘ C
B)   690 ∘\circ∘ C
C)   710 ∘\circ∘ C
D)   730 ∘\circ∘ C
E)   None of the above F) B) and E)
G) B) and C)

Question 17

Which of the following is consistent with a reaction at equilibrium

Accepted Answer

A)   ( Δ\DeltaΔ G)  = 0, Q = K
B)   ( Δ\DeltaΔ G ∘\circ∘ )  = 0, Q > K
C)   ( Δ\DeltaΔ G)  > 0, Q = K
D)   ( Δ\DeltaΔ G)  
E)   ( Δ\DeltaΔ G ∘\circ∘ )  = 0, Q < K F) A) and B)
G) A) and C)

Question 18

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.  ΔH∘f(25∘C) ΔGf∘(25∘C) NO2(g) 33.85 kJ/mol51.8 kJ/molN2O4(g) 9.66 kJ/mol98.29 kJ/mol\begin{array}{lcc}&\Delta \mathrm{H}^{\circ}{ }_{\mathrm{f}}\left(25^{\circ} \mathrm{C}ight)  & \Delta \mathrm{G}^{\circ}_\mathrm{f}\left(25^{\circ} \mathrm{C}ight) \\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}NO2​(g) N2​O4​(g) ​ΔH∘f​(25∘C) 33.85 kJ/mol9.66 kJ/mol​ΔGf∘​(25∘C) 51.8 kJ/mol98.29 kJ/mol​​

Accepted Answer

A)   300 ∘\circ∘ C
B)   28 ∘\circ∘ C
C)   55 ∘\circ∘ C
D)   32 ∘\circ∘ C
E)   562 ∘\circ∘ C F) A) and E)
G) All of the above

Question 19

The reaction 3H2(g) + N2(g) $\leftrightharpoons$ 2NH3(g),(Kc = 9.0 at 350$\circ$C) proceeds from right to left at 350$\circ$C under standard state conditions.

Accepted Answer

A) True 
 B)False

Question 20

Calculate Kp at 298 K for the reaction SO2(g)  + NO2(g)   ⇋\leftrightharpoons⇋  SO3(g)  + NO(g) .  ΔGf∘SO2(g) −300.4 kJ/molSO3(g) −370.4 kJ/molNO(g) 86.7 kJ/molNO2(g) 51.8 kJ/mol\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}SO2​(g) SO3​(g) NO(g) NO2​(g) ​ΔGf∘​−300.4 kJ/mol−370.4 kJ/mol86.7 kJ/mol51.8 kJ/mol​​

Accepted Answer

A)   6.99 * 10-7
B)   5.71 * 10-8
C)   14.2
D)   475
E)   1.42 * 106 F) D) and E)
G) All of the above

Exam 17: Entropy Free Energy and Equilibrium

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Which of the following is consistent with a reaction at equilibrium

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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

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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

Correct Answer
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The reaction 3H₂(g) + N₂(g) $\leftrightharpoons$ 2NH₃(g),(K_c = 9.0 at 350^$\circ$C) proceeds from right to left at 350^$\circ$C under standard state conditions.

Correct Answer
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Predict the signs (-, +, or 0) of $\Delta$ H and $\Delta$ S, in that order, for the reaction: O₂(g) $\rarr$ 2O(g) .

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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]

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For any pure substance, if $\Delta$ H_f^$\circ$ = 0 and $\Delta$ G_f^$\circ$ = 0, then S^$\circ$ = 0.

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

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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)

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At a given temperature, Br₂(l) has a higher entropy per mole than Br₂(g).

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The heat of vaporization of water is 2.27 kJ/g. What is $\Delta$ S_vap per mole at the normal boiling point

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Predict the signs (-, +, or 0) of $\Delta$ H and $\Delta$ S, in that order, for the reaction: 6CO₂(g) + 6H₂O(g) $\rarr$ C₆H₁₂O₆(g) + 6O₂(g) .

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Exam 17: Entropy Free Energy and Equilibrium

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Which of the following is consistent with a reaction at equilibrium

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

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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

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The reaction 3H2(g) + N2(g) ⇋\leftrightharpoons⇋ 2NH3(g),(Kc = 9.0 at 350 ∘\circ∘ C) proceeds from right to left at 350 ∘\circ∘ C under standard state conditions.

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Predict the signs (-, +, or 0) of Δ\DeltaΔ H and Δ\DeltaΔ S, in that order, for the reaction: O2(g) →\rarr→ 2O(g) .

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Determine the equilibrium constant Kp at 25 ∘\circ∘ C for the reaction N2(g) + 3H2(g) ⇋\leftrightharpoons⇋ 2NH3(g) .[ Δ\DeltaΔ G ∘\circ∘ f (NH3(g) ) = -16.6 kJ/mol]

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For any pure substance, if Δ\DeltaΔ Hf ∘\circ∘ = 0 and Δ\DeltaΔ Gf ∘\circ∘ = 0, then S ∘\circ∘ = 0.

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

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Assuming Δ\DeltaΔ S ∘\circ∘ and Δ\DeltaΔ 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) ( Δ\DeltaΔ S ∘\circ∘ = 133.6 J/K·mol; Δ\DeltaΔ H ∘\circ∘ = 131.3 kJ/mol)

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At a given temperature, Br2(l) has a higher entropy per mole than Br2(g).

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The heat of vaporization of water is 2.27 kJ/g. What is Δ\DeltaΔ Svap per mole at the normal boiling point

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Predict the signs (-, +, or 0) of Δ\DeltaΔ H and Δ\DeltaΔ S, in that order, for the reaction: 6CO2(g) + 6H2O(g) →\rarr→ C6H12O6(g) + 6O2(g) .

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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

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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

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The reaction 3H₂(g) + N₂(g) $\leftrightharpoons$ 2NH₃(g),(K_c = 9.0 at 350^$\circ$C) proceeds from right to left at 350^$\circ$C under standard state conditions.

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Predict the signs (-, +, or 0) of $\Delta$ H and $\Delta$ S, in that order, for the reaction: O₂(g) $\rarr$ 2O(g) .

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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]

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For any pure substance, if $\Delta$ H_f^$\circ$ = 0 and $\Delta$ G_f^$\circ$ = 0, then S^$\circ$ = 0.

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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)

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At a given temperature, Br₂(l) has a higher entropy per mole than Br₂(g).

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The heat of vaporization of water is 2.27 kJ/g. What is $\Delta$ S_vap per mole at the normal boiling point

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Predict the signs (-, +, or 0) of $\Delta$ H and $\Delta$ S, in that order, for the reaction: 6CO₂(g) + 6H₂O(g) $\rarr$ C₆H₁₂O₆(g) + 6O₂(g) .

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