Question 1

Consider a reaction that has a positive ΔrH and a positive ΔrS.Which of the following statements is TRUE?

Accepted Answer

A) This reaction will be spontaneous only at high temperatures. 
B) This reaction will be spontaneous at all temperatures. 
C) This reaction will be nonspontaneous at all temperatures. 
D) This reaction will be nonspontaneous only at high temperatures. 
E) This reaction will be spontaneous only at very low temperatures. 
A) This reaction will be spontaneous only at high temperatures. 
B) This reaction will be spontaneous at all temperatures. 
C) This reaction will be nonspontaneous at all temperatures. 
D) This reaction will be nonspontaneous only at high temperatures. 
E) This reaction will be spontaneous only at very low temperatures. A

Question 2

Define allotrope.

Accepted Answer

An allotrope is two or more forms of an element existing in the same state.

Question 3

Determine the equilibrium constant for the following reaction at 549 K: CH2O(g)+ 2H2(g)→ CH4(g)+ H2O(g)$\quad$$\quad$ΔrH° = -94.9 kJ mol-1; ΔrS°= -224.2 J K-1 mol-1

Accepted Answer

A) 481 
B) 1.07 × 109 
C) 2.08 × 10-3 
D) 9.35 × 10-10 
E) 1.94 × 10-12 
A) 481 
B) 1.07 × 109 
C) 2.08 × 10-3 
D) 9.35 × 10-10 
E) 1.94 × 10-12 C

Question 4

Identify the compound with the standard Gibbs energy of formation equal to zero.

Accepted Answer

A) NaCl(s) 
B) N2(g) 
C) NO(g) 
D) O3(g) 
E) HCl(g) 
A) NaCl(s) 
B) N2(g) 
C) NO(g) 
D) O3(g) 
E) HCl(g)

Question 5

Which of the following processes have a ΔrS > 0?

Accepted Answer

A) 2NH3(g)+ CO2(g)→ NH2CONH2(aq)+ H2O(l) 
B) lithium fluoride forms from Li and F2 
C) 2HBr(g)→ H2(g)+ Br2(l) 
D) sodium chloride dissolves in pure water 
E) Ag+(aq)+ Cl-(aq)→ AgCl(s) 
A) 2NH3(g)+ CO2(g)→ NH2CONH2(aq)+ H2O(l) 
B) lithium fluoride forms from Li and F2 
C) 2HBr(g)→ H2(g)+ Br2(l) 
D) sodium chloride dissolves in pure water 
E) Ag+(aq)+ Cl-(aq)→ AgCl(s)

Question 6

Which of the following statements is TRUE?

Accepted Answer

A) Entropy is not a state function. 
B) Endothermic processes decrease the entropy of the surroundings,at constant T and P. 
C) Endothermic processes are never spontaneous. 
D) Exothermic processes are always spontaneous. 
E) Entropy of the universe is a constant value. 
A) Entropy is not a state function. 
B) Endothermic processes decrease the entropy of the surroundings,at constant T and P. 
C) Endothermic processes are never spontaneous. 
D) Exothermic processes are always spontaneous. 
E) Entropy of the universe is a constant value.

Question 7

Use the free energies of formation given below to calculate the equilibrium constant (K)for the following reaction at 298 K: 
$\quad$$\quad$$\quad$$\quad$$\quad$2HNO3(aq)+ NO(g)→ 3 NO2(g)+ H2O(l)$\quad$$\quad$K = ?
ΔfG° (kJ mol-1)-110.9 $\quad$$\quad$87.6 $\quad$$\quad$51.3 $\quad$-237.1

Accepted Answer

A) 8.71 × 108 
B) 0.980 
C) 1.15 × 10-9 
D) 1.02 
E) 5.11 × 10-4 
A) 8.71 × 108 
B) 0.980 
C) 1.15 × 10-9 
D) 1.02 
E) 5.11 × 10-4

Question 8

Define entropy.

Accepted Answer

Entropy is a thermodynamic fun

Question 9

Identify the compound with the highest standard Gibbs energy of formation.

Accepted Answer

A) NaCl(s) 
B) N2(g) 
C) NO(g) 
D) O3(g) 
E) Cl2(g) 
A) NaCl(s) 
B) N2(g) 
C) NO(g) 
D) O3(g) 
E) Cl2(g)

Question 10

Calculate ΔρS° for the following reaction.The S° for each species is shown below the reaction. 
$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$P4(g)+ 10Cl2(g)→ 4PCl5(g)
S°(J K-1 mol-1)$\quad$$\quad$$\quad$280.0 $\quad$223.1 $\quad$$\quad$364.6

Accepted Answer

A) -138.5 J K-1 mol-1 
B) -1052.6 J K-1 mol-1 
C) +171.3 J K-1 mol-1 
D) -583.6 J K-1 mol-1 
E) +2334.6 J K-1 mol-1 
A) -138.5 J K-1 mol-1 
B) -1052.6 J K-1 mol-1 
C) +171.3 J K-1 mol-1 
D) -583.6 J K-1 mol-1 
E) +2334.6 J K-1 mol-1

Question 11

The value of ?fG° at 400.0 °C for the formation of calcium chloride from its constituent elements, Ca(s)+ $\mathrm { Cl } _ { 2 }$ (g)? $\mathrm { CaCl } _ { 2 }$ (s)
Is ________ kJ mol-1.At 25.0 °C for this reaction,?fH° is -795.8 kJ mol-1,?fG° is -748.1 kJ mol-1,and $\Delta _ { \mathrm { f } } S ^ { \circ }$ is $- 159.8 \mathrm {~J} \mathrm {~K} ^ { - 1 } \mathrm {~mol} ^ { - 1 }$

Accepted Answer

A) -731.9 
B) -903.3 
C) 1.07 × 105 
D) 6.31 × 104 
E) -688.3 
A) -731.9 
B) -903.3 
C) 1.07 × 105 
D) 6.31 × 104 
E) -688.3

Question 12

Determine the temperature of a reaction if ΔrG° = 6.21 kJ mol-1,ΔrG = -8.34 kJ mol-1,and Q = 0.0100

Accepted Answer

A) 273 K 
B) 49.6 K 
C) 380 K 
D) 448 K 
E) 298 K 
A) 273 K 
B) 49.6 K 
C) 380 K 
D) 448 K 
E) 298 K

Question 13

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 14

Which of the following is TRUE regarding allotropes?

Accepted Answer

A) Allotropes are different forms of the same element,but they have identical standard molar enthalpies. 
B) Allotropes are different forms of the same element and have different standard molar enthalpies. 
C) Allotropes are composed of different isotopes of the same element and have different standard molar enthalpies. 
D) Allotropes are composed of different isotopes of the same element and identical standard molar enthalpies. 
E) Allotropes are different elements with the same structure and have different standard molar enthalpies. 
A) Allotropes are different forms of the same element,but they have identical standard molar enthalpies. 
B) Allotropes are different forms of the same element and have different standard molar enthalpies. 
C) Allotropes are composed of different isotopes of the same element and have different standard molar enthalpies. 
D) Allotropes are composed of different isotopes of the same element and identical standard molar enthalpies. 
E) Allotropes are different elements with the same structure and have different standard molar enthalpies.

Question 15

Calculate the equilibrium constant for the following reaction at 525 K: 
$\quad$2CO(g)+ O2(g)→ 2CO2(g)$\quad$$\quad$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 16

Calculate the equilibrium constant for the following reaction at 525 K: 2H2S(g)→ 2H2(g)+ S2(g)$\quad$$\quad$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 17

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

Accepted Answer

A) I2(s) 
B) F2(g) 
C) Br2(l) 
D) N2(g) 
E) Cl2(g) 
A) I2(s) 
B) F2(g) 
C) Br2(l) 
D) N2(g) 
E) Cl2(g)

Question 18

Define the second law of thermodynamics.

Accepted Answer

For any spontaneous

Question 19

For a given reaction,ΔrH = +35.5 kJ mol-1 and ΔrS = +83.6 J K-1 mol-1.The reaction is spontaneous ________.Assume that ΔrH and ΔrS do not vary with temperature.

Accepted Answer

A) at T 298 K C) at all temperatures D) at T > 425 K E) at T < 298 K A) at T 298 K C) at all temperatures D) at T > 425 K E) at T < 298 K

Question 20

Calculate ΔrG° at 298 K using the following information: 
$\quad$$\quad$$\quad$$\quad$$\quad$4HNO3(g)+ 5N2H4(l)→ 7N2(g)+ 12H2O(l)ΔrG° = ?
ΔfG° (kJ mol-1)$\quad$-73.5 $\quad$$\quad$149.3 $\quad$$\quad$ -237.1

Accepted Answer

A) -3.2977 × 103 kJ mol-1 
B) -312.9 kJ mol-1 
C) +2.845 × 103 kJ mol-1 
D) +110.7 kJ mol-1 
E) -954.7 kJ mol-1 
A) -3.2977 × 103 kJ mol-1 
B) -312.9 kJ mol-1 
C) +2.845 × 103 kJ mol-1 
D) +110.7 kJ mol-1 
E) -954.7 kJ mol-1

Exam 17: Gibbs Energy and Thermodynamics

Consider a reaction that has a positive ΔrH and a positive ΔrS.Which of the following statements is TRUE?

Define allotrope.

Determine the equilibrium constant for the following reaction at 549 K: CH2O(g)+ 2H2(g)→ CH4(g)+ H2O(g) \quad\quad ΔrH° = -94.9 kJ mol-1; ΔrS°= -224.2 J K-1 mol-1

Identify the compound with the standard Gibbs energy of formation equal to zero.

Which of the following processes have a ΔrS > 0?

Which of the following statements is TRUE?

Use the free energies of formation given below to calculate the equilibrium constant (K)for the following reaction at 298 K: \quad\quad\quad\quad\quad 2HNO3(aq)+ NO(g)→ 3 NO2(g)+ H2O(l) \quad\quad K = ? ΔfG° (kJ mol-1)-110.9 \quad\quad 87.6 \quad\quad 51.3 \quad -237.1

Define entropy.

Identify the compound with the highest standard Gibbs energy of formation.

Calculate ΔρS° for the following reaction.The S° for each species is shown below the reaction. \quad\quad\quad\quad\quad\quad\quad\quad P4(g)+ 10Cl2(g)→ 4PCl5(g) S°(J K-1 mol-1) \quad\quad\quad 280.0 \quad 223.1 \quad\quad 364.6

Determine the temperature of a reaction if ΔrG° = 6.21 kJ mol-1,ΔrG = -8.34 kJ mol-1,and Q = 0.0100

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

Which of the following is TRUE regarding allotropes?

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

Calculate the equilibrium constant for the following reaction at 525 K: 2H2S(g)→ 2H2(g)+ S2(g) \quad\quad 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?

Define the second law of thermodynamics.

For a given reaction,ΔrH = +35.5 kJ mol-1 and ΔrS = +83.6 J K-1 mol-1.The reaction is spontaneous ________.Assume that ΔrH and ΔrS do not vary with temperature.

Calculate ΔrG° at 298 K using the following information: \quad\quad\quad\quad\quad 4HNO3(g)+ 5N2H4(l)→ 7N2(g)+ 12H2O(l)ΔrG° = ? ΔfG° (kJ mol-1) \quad -73.5 \quad\quad 149.3 \quad\quad -237.1

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Filters

Consider a reaction that has a positive Δ_rH and a positive Δ_rS.Which of the following statements is TRUE?

Determine the equilibrium constant for the following reaction at 549 K: CH₂O(g)+ 2H₂(g)→ CH₄(g)+ H₂O(g) $\quad$ $\quad$ Δ_rH° = -94.9 kJ mol^-1; Δ_rS°= -224.2 J K^-1 mol^-1

Which of the following processes have a Δ_rS > 0?

Calculate ΔρS° for the following reaction.The S° for each species is shown below the reaction. $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ P₄(g)+ 10Cl₂(g)→ 4PCl₅(g) S°(J K^-1 mol^-1) $\quad$ $\quad$ $\quad$ 280.0 $\quad$ 223.1 $\quad$ $\quad$ 364.6

Determine the temperature of a reaction if Δ_rG° = 6.21 kJ mol^-1,Δ_rG = -8.34 kJ mol^-1,and Q = 0.0100

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

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

For a given reaction,Δ_rH = +35.5 kJ mol^-1 and Δ_rS = +83.6 J K^-1mol^-1.The reaction is spontaneous ________.Assume that Δ_rH and Δ_rS do not vary with temperature.

Calculate Δ_rG° at 298 K using the following information: $\quad$ $\quad$ $\quad$ $\quad$ $\quad$ 4HNO₃(g)+ 5N₂H₄(l)→ 7N₂(g)+ 12H₂O(l)Δ_rG°= ? Δ_fG° (kJ mol^-1) $\quad$ -73.5 $\quad$ $\quad$ 149.3 $\quad$ $\quad$ -237.1