Question 1

What is "free" energy? Give a fictitious example.

Accepted Answer

Consider a reaction that is exothermic (

Question 2

For a given reaction, ΔrH = -19.5 kJ mol-1 and ΔrS = -55.8 J K-1 mol-1. The reaction will have   at   Assume that ΔrH and ΔrS do not vary with temperature.

Accepted Answer

A)  2.86 
B)  0.349 
C)  298 
D)  2.86 × 103 
E)  349 
A)  2.86 
B)  0.349 
C)  298 
D)  2.86 × 103 
E)  349

Question 3

For the following example, what is true about ΔrH and ΔrS? H2O(l) → H2O(s)

Accepted Answer

A)  a negative ΔrH and a negative ΔrS 
B)  a positive ΔrH and a negative ΔrS 
C)  a negative ΔrH and a positive ΔrS 
D)  a positive ΔrH and a positive ΔrS 
E)  ΔrH = 0 and a positive ΔrS 
A)  a negative ΔrH and a negative ΔrS 
B)  a positive ΔrH and a negative ΔrS 
C)  a negative ΔrH and a positive ΔrS 
D)  a positive ΔrH and a positive ΔrS 
E)  ΔrH = 0 and a positive ΔrS

Question 4

Above what temperature does the following reaction become nonspontaneous? 2H2S(g) + 3O2(g) → 2SO2(g) + 2H2O(g) ΔrH = -1036 kJ; ΔrS = -153.2 J K-1 mol-1

Accepted Answer

A)  6.762 × 103 K 
B)  158.7 K 
C)  298 K 
D)  67.62 K 
E)  1.587 × 103 K 
A)  6.762 × 103 K 
B)  158.7 K 
C)  298 K 
D)  67.62 K 
E)  1.587 × 103 K

Question 5

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 6

Use the following thermodynamic values to calculate Δr NEWLINE   .
Δr
    = -95 kJ   , Δr
    = -157 J   , T = 855 K

Accepted Answer

A)  -48 kJ   
B)  -68 kJ   
C)  +39 kJ   
D)  -157 kJ   
E)  +142 kJ   
A)  -48 kJ   
B)  -68 kJ   
C)  +39 kJ   
D)  -157 kJ   
E)  +142 kJ

Question 7

Calculate the equilibrium constant for the following reaction at 525 K: 2H2S(g) → 2H2(g) + S2(g) ΔrH° = 169.8 kJ mol-1; ΔrS°= 78.0 J K-1 mol-1

Accepted Answer

A)  3.84 × 10-11 
B)  1.51 × 10-13 
C)  4.08 × 10-17 
D)  7.52 × 10-19 
E)  6.18 × 10-15 
A)  3.84 × 10-11 
B)  1.51 × 10-13 
C)  4.08 × 10-17 
D)  7.52 × 10-19 
E)  6.18 × 10-15

Question 8

Which one of the following has the highest standard molar entropy, S°, at 25 °C?

Accepted Answer

A)  H2(g) 
B)  F2(g) 
C)  O2(g) 
D)  N2(g) 
E)  Cl2(g) 
A)  H2(g) 
B)  F2(g) 
C)  O2(g) 
D)  N2(g) 
E)  Cl2(g)

Question 9

Calculate ΔrS° for the following reaction. The S° for each species is shown below the reaction. N2H4(l) + H2(g) → 2NH3(g)
S° (J K-1 mol-1) 121.2 130.7 192.8

Accepted Answer

A)  +133.7 J K-1 mol-1 
B)  -59.1 J K-1 mol-1 
C)  +118.2 J K-1 mol-1 
D)  -202.3 J K-1 mol-1 
E)  +178.9 J K-1 mol-1 
A)  +133.7 J K-1 mol-1 
B)  -59.1 J K-1 mol-1 
C)  +118.2 J K-1 mol-1 
D)  -202.3 J K-1 mol-1 
E)  +178.9 J K-1 mol-1

Question 10

Calculate ΔrS° for the following reaction. The S° for each species is shown below the reaction. C2H2(g) + H2(g) → C2H4(g)
S°(J J K-1 mol-1) 200.9 130.7 219.3

Accepted Answer

A)  +112.3 J K-1 mol-1 
B)  +550.9 J K-1 mol-1 
C)  -112.3 J K-1 mol-1 
D)  +337.1 J K-1 mol-1 
E)  -550.9 J K-1 mol-1 
A)  +112.3 J K-1 mol-1 
B)  +550.9 J K-1 mol-1 
C)  -112.3 J K-1 mol-1 
D)  +337.1 J K-1 mol-1 
E)  -550.9 J K-1 mol-1

Question 11

Determine the equilibrium constant for the following reaction at 655 K: HCN(g) + 2H2(g) → CH3NH2(g) ΔrH° = -158 kJ mol-1; ΔrS°= -219.9 J K-1 mol-1

Accepted Answer

A)  3.99 × 1012 
B)  13.0 
C)  2.51 × 10-13 
D)  3.26 × 10-12 
E)  3.07 × 1011 
A)  3.99 × 1012 
B)  13.0 
C)  2.51 × 10-13 
D)  3.26 × 10-12 
E)  3.07 × 1011

Question 12

Which one of the following would be expected to have the lowest standard molar entropy, S°, at 25 °C?

Accepted Answer

A)  C10H22(s) 
B)  C10H22(l) 
C)  C14H30(s) 
D)  C14     OH(l) 
A)  C10H22(s) 
B)  C10H22(l) 
C)  C14H30(s) 
D)  C14     OH(l)

Question 13

Determine ΔrG° at 298 K using the following information: 2KClO3(s) → 2KCl(s) + 3O2(g) ΔrH°= -77.6 kJ mol-1; ΔrS°= +494.6 J K-1 mol-1

Accepted Answer

A)  -225.0 kJ mol-1 
B)  +68.4 .0 kJ mol-1 
C)  -89.3 kJ mol-1 
D)  +131.5 kJ mol-1 
E)  +175.2 kJ mol-1 
A)  -225.0 kJ mol-1 
B)  +68.4 .0 kJ mol-1 
C)  -89.3 kJ mol-1 
D)  +131.5 kJ mol-1 
E)  +175.2 kJ mol-1

Question 14

Calculate ΔrG for the evaporation of methanol at 25°C under nonstandard conditions when   = 150.0 mbar CH3OH(l) → CH3OH(g)

Accepted Answer

A)  -0.40 kJ mol-1 
B)  +9.0 kJ mol-1 
C)  -0.47 kJ mol-1 
D)  +4.3 kJ mol-1 
E)  +16 kJ mol-1 
A)  -0.40 kJ mol-1 
B)  +9.0 kJ mol-1 
C)  -0.47 kJ mol-1 
D)  +4.3 kJ mol-1 
E)  +16 kJ mol-1

Question 15

Under which of the following conditions would one mole of He have the highest entropy, S?

Accepted Answer

A)  17 °C and 15 L 
B)  127 °C and 15 L 
C)  17 °C and 25 L 
D)  127 °C and 25 L 
A)  17 °C and 15 L 
B)  127 °C and 15 L 
C)  17 °C and 25 L 
D)  127 °C and 25 L

Question 16

Which one of the following has the highest standard molar entropy, S°, at 25 °C?

Accepted Answer

A)  NH3(g) 
B)  Ne(g) 
C)  SO2(g) 
D)  CH3CH2OH(g) 
E)  He (g) 
A)  NH3(g) 
B)  Ne(g) 
C)  SO2(g) 
D)  CH3CH2OH(g) 
E)  He (g)

Question 17

Calculate the equilibrium constant for the following reaction at 525 K: 2CO(g) + O2(g) → 2CO2(g) ΔrH° = -566 kJ mol-1; ΔrS°= -173 J K-1 mol-1

Accepted Answer

A)  3.61 × 1058 
B)  1.90 × 1047 
C)  2.47 × 1014 
D)  7.56 × 1084 
E)  8.49 × 106 
A)  3.61 × 1058 
B)  1.90 × 1047 
C)  2.47 × 1014 
D)  7.56 × 1084 
E)  8.49 × 106

Question 18

Determine the Q of a reaction at 298 K if ΔrG = -3.5 kJ mol-1 and ΔrG° = +19.3 kJ mol-1.

Accepted Answer

A)  0.10 
B)  0.0010 
C)  0.00010 
D)  0.34 
E)  0.89 
A)  0.10 
B)  0.0010 
C)  0.00010 
D)  0.34 
E)  0.89

Question 19

Which of the following is true for ΔrG?

Accepted Answer

A)  If ΔrG > 0, the reaction is spontaneous in the forward direction. 
B)  If Q = 1, then DrG > ΔrG. 
C)  If ΔrG ≠ 0, the reaction is spontaneous in both the reverse and forward directions. 
D)  If ΔrG rG = 0. 
A)  If ΔrG > 0, the reaction is spontaneous in the forward direction. 
B)  If Q = 1, then DrG > ΔrG. 
C)  If ΔrG ≠ 0, the reaction is spontaneous in both the reverse and forward directions. 
D)  If ΔrG rG = 0.

Question 20

Place the following in order of increasing molar entropy at 298 K. Ne Xe He Ar Kr

Accepted Answer

A)  He < Kr < Ne < Ar < Xe 
B)  Xe < Kr < Ar < Ne < He 
C)  Ar < He < Ar < Ne < Kr 
D)  Ar < Ne < Xe < Kr < He 
E)  He < Ne < Ar < Kr < Xe 
A)  He < Kr < Ne < Ar < Xe 
B)  Xe < Kr < Ar < Ne < He 
C)  Ar < He < Ar < Ne < Kr 
D)  Ar < Ne < Xe < Kr < He 
E)  He < Ne < Ar < Kr < Xe

Exam 17: Gibbs Energy and Thermodynamics

What is "free" energy? Give a fictitious example.

For a given reaction, ΔrH = -19.5 kJ mol-1 and ΔrS = -55.8 J K-1 mol-1. The reaction will have at Assume that ΔrH and ΔrS do not vary with temperature.

For the following example, what is true about ΔrH and ΔrS? H2O(l) → H2O(s)

Above what temperature does the following reaction become nonspontaneous? 2H2S(g) + 3O2(g) → 2SO2(g) + 2H2O(g) ΔrH = -1036 kJ; ΔrS = -153.2 J K-1 mol-1

Match the following. -Q = K

Use the following thermodynamic values to calculate Δr NEWLINE . Δr = -95 kJ , Δr = -157 J , T = 855 K

Calculate the equilibrium constant for the following reaction at 525 K: 2H2S(g) → 2H2(g) + S2(g) ΔrH° = 169.8 kJ mol-1; ΔrS°= 78.0 J K-1 mol-1

Which one of the following has the highest standard molar entropy, S°, at 25 °C?

Calculate ΔrS° for the following reaction. The S° for each species is shown below the reaction. N2H4(l) + H2(g) → 2NH3(g) S° (J K-1 mol-1) 121.2 130.7 192.8

Calculate ΔrS° for the following reaction. The S° for each species is shown below the reaction. C2H2(g) + H2(g) → C2H4(g) S°(J J K-1 mol-1) 200.9 130.7 219.3

Determine the equilibrium constant for the following reaction at 655 K: HCN(g) + 2H2(g) → CH3NH2(g) ΔrH° = -158 kJ mol-1; ΔrS°= -219.9 J K-1 mol-1

Which one of the following would be expected to have the lowest standard molar entropy, S°, at 25 °C?

Determine ΔrG° at 298 K using the following information: 2KClO3(s) → 2KCl(s) + 3O2(g) ΔrH°= -77.6 kJ mol-1; ΔrS°= +494.6 J K-1 mol-1

Calculate ΔrG for the evaporation of methanol at 25°C under nonstandard conditions when = 150.0 mbar CH3OH(l) → CH3OH(g)

Under which of the following conditions would one mole of He have the highest entropy, S?

Which one of the following has the highest standard molar entropy, S°, at 25 °C?

Calculate the equilibrium constant for the following reaction at 525 K: 2CO(g) + O2(g) → 2CO2(g) ΔrH° = -566 kJ mol-1; ΔrS°= -173 J K-1 mol-1

Determine the Q of a reaction at 298 K if ΔrG = -3.5 kJ mol-1 and ΔrG° = +19.3 kJ mol-1.

Which of the following is true for ΔrG?

Place the following in order of increasing molar entropy at 298 K. Ne Xe He Ar Kr

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For a given reaction, Δ_rH = -19.5 kJ mol^-1 and Δ_rS = -55.8 J K^-¹ mol^-1. The reaction will have at Assume that Δ_rH and Δ_rS do not vary with temperature.

For the following example, what is true about Δ_rH and Δ_rS? H₂O(l) → H₂O(s)

Above what temperature does the following reaction become nonspontaneous? 2H₂S(g) + 3O₂(g) → 2SO₂(g) + 2H₂O(g) Δ_rH = -1036 kJ; Δ_rS = -153.2 J K^-1 mol^-1

Use the following thermodynamic values to calculate Δ_r _NE_WLINE . Δ_r = -95 kJ , Δ_r = -157 J , T = 855 K

Calculate the equilibrium constant for the following reaction at 525 K: 2H₂S(g) → 2H₂(g) + S₂(g) Δ_rH° = 169.8 kJ mol^-1; Δ_rS°= 78.0 J K^-1 mol^-1

Calculate Δ_rS° for the following reaction. The S° for each species is shown below the reaction. N₂H₄(l) + H₂(g) → 2NH₃(g) S° (J K^-1 mol^-1) 121.2 130.7 192.8

Calculate Δ_rS° for the following reaction. The S° for each species is shown below the reaction. C₂H₂(g) + H₂(g) → C₂H₄(g) S°(J J K^-1 mol^-1) 200.9 130.7 219.3

Determine the equilibrium constant for the following reaction at 655 K: HCN(g) + 2H₂(g) → CH₃NH₂(g) Δ_rH° = -158 kJ mol^-1; Δ_rS°= -219.9 J K^-1 mol^-1

Determine Δ_rG° at 298 K using the following information: 2KClO₃(s) → 2KCl(s) + 3O₂(g) Δ_rH°= -77.6 kJ mol^-1; Δ_rS°= +494.6 J K^-1 mol^-¹

Calculate Δ_rG for the evaporation of methanol at 25°C under nonstandard conditions when = 150.0 mbar CH₃OH(l) → CH₃OH(g)

Calculate the equilibrium constant for the following reaction at 525 K: 2CO(g) + O₂(g) → 2CO₂(g) Δ_rH° = -566 kJ mol^-1; Δ_rS°= -173 J K^-1 mol^-1

Determine the Q of a reaction at 298 K if Δ_rG = -3.5 kJ mol^-1 and Δ_rG° = +19.3 kJ mol^-1.

Which of the following is true for Δ_rG?