Question 1

ΔS is positive for the reaction ________.

Accepted Answer

A) Pb(NO3)2 (aq) + 2KI(aq) → PbI2 (s) + 2KNO3 (aq) 
B) 2H2O (g) → 2H2 (g) + O2 (g) 
C) H2O (g) → H2O (s) 
D) NO (g) + O2 (g) → NO2 (g) 
E) Ag+ (aq) + Cl- (aq) → AgCl (s) 
A) Pb(NO3)2 (aq) + 2KI(aq) → PbI2 (s) + 2KNO3 (aq) 
B) 2H2O (g) → 2H2 (g) + O2 (g) 
C) H2O (g) → H2O (s) 
D) NO (g) + O2 (g) → NO2 (g) 
E) Ag+ (aq) + Cl- (aq) → AgCl (s)

Question 2

Calculate ΔG° (in kJ/mol)for the following reaction at 1 atm and 25 °C:
C2H6 (g)+ O2 (g)→ CO2 (g)+ H2O (l) (unbalanced)
ΔGf° C2H6 (g)= -32.89 kJ/mol; ΔGf° CO2 (g)= -394.4 kJ/mol; ΔGf° H2O (l)= -237.13 kJ/mol

Accepted Answer

Question 3

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25 °C)
Substance ΔH°f (kJ/mol)ΔG°f (kJ/mol)S (J/K-mol)
Carbon
C (s, diamond)1.88 2.84 2.43
C (s, graphite)0 0 5.69
CS1U1B12S1U1B0HS1U1B12S1U1B0 (g)226.7 209.2 200.8
CS1U1B12S1U1B0HS1U1B14S1U1B0 (g)52.30 68.11 219.4
CS1U1B12S1U1B0HS1U1B16S1U1B0 (g)-84.68 -32.89 229.5
CO (g)-110.5 -137.2 197.9
COS1U1B12S1U1B0 (g)-393.5 -394.4 213.6
Hydrogen
HS1U1B12S1U1B0( g)0 0 130.58
Oxygen
OS1U1B12S1U1B0 (g)0 0 205.0
HS1U1B12S1U1B0O (l)-285.83 -237.13 69.91
-The combustion of acetylene in the presence of excess oxygen yields carbon dioxide and water: 2C2H2 (g) + 5O2 (g) → 4CO2 (g) + 2H2O (l)
The value of ΔS° for this reaction is ________ J/K ∙ mol.

Accepted Answer

A) +689.3 
B) +122.3 
C) +432.4 
D) -122.3 
E) -432.4 
A) +689.3 
B) +122.3 
C) +432.4 
D) -122.3 
E) -432.4

Question 4

Of the following, the entropy of gaseous ________ is the largest at 25 °C and 1 atm.

Accepted Answer

A) C3H8 
B) C3H6 
C) C3H4 
D) C2H6 
E)    
A) C3H8 
B) C3H6 
C) C3H4 
D) C2H6 
E)

Question 5

Which reaction produces a decrease in the entropy of the system?

Accepted Answer

A) 4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g) 
B) Na (s) + 1/2 Cl2 (g) → NaCl (s) 
C) 2 HgO (s) → 2 Hg (l) + O2 (g) 
D) UF6 (s)→ U (s) + 3F2 (g) 
E) H2O (s) → H2O (g) 
A) 4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g) 
B) Na (s) + 1/2 Cl2 (g) → NaCl (s) 
C) 2 HgO (s) → 2 Hg (l) + O2 (g) 
D) UF6 (s)→ U (s) + 3F2 (g) 
E) H2O (s) → H2O (g)

Question 6

The value of ΔG° at 25 °C for the following reaction: C2H4 (g) + H2 (g) → C2H6 (g)
Is ________ kJ/mol. At 298 K, ΔH° for this reaction is -137.5 kJ/mol, and ΔS° is +120.5 J/K.

Accepted Answer

A) -35800 
B) -173.4 
C) 35800 
D) -101.7 
E) -274.2 
A) -35800 
B) -173.4 
C) 35800 
D) -101.7 
E) -274.2

Question 7

The value of ΔH° for the decomposition of gaseous sulfur trioxide to its component elements, 2SO3 (g) → 2S (s, rhombic) + 3O2 (g)
Is ________ kJ/mol.

Accepted Answer

A) +790.4 
B) -790.4 
C) +395.2 
D) -395.2 
E) +105.1 
A) +790.4 
B) -790.4 
C) +395.2 
D) -395.2 
E) +105.1

Question 8

Which one of the following is always positive when a spontaneous process occurs?

Accepted Answer

A) ΔSsystem 
B) ΔSsurroundings 
C) ΔSuniverse 
D) ΔHuniverse 
E) ΔHsurroundings 
A) ΔSsystem 
B) ΔSsurroundings 
C) ΔSuniverse 
D) ΔHuniverse 
E) ΔHsurroundings

Question 9

The equilibrium constant for the following reaction is 3.0 × 108 at 25 °C. N2 (g) + 3H2 (g)   2NH3 (g)
The value of ΔG° for this reaction is ________ kJ/mol.

Accepted Answer

A) 22 
B) -4.1 
C) 4.1 
D) -48 
E) -22 
A) 22 
B) -4.1 
C) 4.1 
D) -48 
E) -22

Question 10

Consider the reaction: NH3 (g) + HCl (g) → NH4Cl (s)
Given the following table of thermodynamic data,   determine the temperature (in °C)above which the reaction is nonspontaneous.

Accepted Answer

A) This reaction is spontaneous at all temperatures. 
B) 618.1 
C) 432.8 
D) 345.0 
E) 1235 
A) This reaction is spontaneous at all temperatures. 
B) 618.1 
C) 432.8 
D) 345.0 
E) 1235

Question 11

Of the following, only ________ is not a state function.

Accepted Answer

A) S 
B) H 
C) q 
D) E 
E) T 
A) S 
B) H 
C) q 
D) E 
E) T

Question 12

When a system is at equilibrium, ________.

Accepted Answer

A) the reverse process is spontaneous but the forward process is not 
B) the forward and the reverse processes are both spontaneous 
C) the forward process is spontaneous but the reverse process is not 
D) the process is not spontaneous in either direction 
E) both forward and reverse processes have stopped 
A) the reverse process is spontaneous but the forward process is not 
B) the forward and the reverse processes are both spontaneous 
C) the forward process is spontaneous but the reverse process is not 
D) the process is not spontaneous in either direction 
E) both forward and reverse processes have stopped

Question 13

Which of the following statements is false?

Accepted Answer

A) The change in entropy in a system depends on the initial and final states of the system and the path taken from one state to the other. 
B) Any irreversible process results in an overall increase in entropy. 
C) The total entropy of the universe increases in any spontaneous process. 
D) Entropy increases with the number of microstates of the system. 
A) The change in entropy in a system depends on the initial and final states of the system and the path taken from one state to the other. 
B) Any irreversible process results in an overall increase in entropy. 
C) The total entropy of the universe increases in any spontaneous process. 
D) Entropy increases with the number of microstates of the system.

Question 14

Phosphorous and chlorine gases combine to produce phosphorous trichloride: P2 (g) + 3Cl2 (g) → 2PCl3 (g)
ΔG° at 298 K for this reaction is -642.9 kJ/mol. The value of ΔG at 298 K for a reaction mixture that consists of 1.9 atm P2, 1.6 atm Cl2, and 0.65 atm PCl3 is ________.

Accepted Answer

A) -34.9 
B) -4.46 × 103 
C) -7.86 × 103 
D) -714.1 
E) -650.1 
A) -34.9 
B) -4.46 × 103 
C) -7.86 × 103 
D) -714.1 
E) -650.1

Question 15

The value of ΔS° for the formation of phosphorous trichloride from its constituent elements, P2 (g) + 3Cl2 (g) → 2PCl3 (g)
Is ________ J/K ∙ mol.

Accepted Answer

A) -311.7 
B) +311.7 
C) -263.6 
D) +129.4 
E) -129.4 
A) -311.7 
B) +311.7 
C) -263.6 
D) +129.4 
E) -129.4

Question 16

For a given reaction, ΔH = +22.2 kJ/mol and ΔS = +81.1 J/K-mol. The reaction is spontaneous ________. Assume that ΔH and ΔS do not vary with temperature.

Accepted Answer

A) at T 274 K C) at T > 298 K D) at T < 298 K E) at all temperatures A) at T 274 K C) at T > 298 K D) at T < 298 K E) at all temperatures

Question 17

The combustion of ethane in the presence of excess oxygen yields carbon dioxide and water: 2C2H6 (g) + 7O2 (g) → 4CO2 (g) + 6H2O (l)
The value of ΔS° for this reaction is ________ J/K ∙ mol.

Accepted Answer

A) +718.0 
B) -620.1 
C) -718.0 
D) -151.0 
E) +151.0 
A) +718.0 
B) -620.1 
C) -718.0 
D) -151.0 
E) +151.0

Question 18

Which reaction produces an increase in the entropy of the system?

Accepted Answer

A) Ag+ (aq) + Cl- (aq) → AgCl (s) 
B) CO2 (s) → CO2 (g) 
C) H2 (g) + Cl2 (g) → 2 HCl (g) 
D) N2 (g) + 3 H2 (g) → 2 NH3 (g) 
E) H2O (l) → H2O (s) 
A) Ag+ (aq) + Cl- (aq) → AgCl (s) 
B) CO2 (s) → CO2 (g) 
C) H2 (g) + Cl2 (g) → 2 HCl (g) 
D) N2 (g) + 3 H2 (g) → 2 NH3 (g) 
E) H2O (l) → H2O (s)

Question 19

A reversible change produces the maximum amount of ________ that can be achieved by the system on the surroundings.

Accepted Answer

The answer of A reversible change produces the maximum amount...

Question 20

Consider the reaction: Ag+ (aq) + Cl- (aq) → AgCl (s)
Given the following table of thermodynamic data,   determine the temperature (in °C)above which the reaction is nonspontaneous under standard conditions.

Accepted Answer

A) 1230 
B) 150 
C) 432 
D) 133 
E) 1640 
A) 1230 
B) 150 
C) 432 
D) 133 
E) 1640

Exam 19: Chemical Thermodynamics

ΔS is positive for the reaction ________.

Calculate ΔG° (in kJ/mol)for the following reaction at 1 atm and 25 °C: C2H6 (g)+ O2 (g)→ CO2 (g)+ H2O (l) (unbalanced) ΔGf° C2H6 (g)= -32.89 kJ/mol; ΔGf° CO2 (g)= -394.4 kJ/mol; ΔGf° H2O (l)= -237.13 kJ/mol

Of the following, the entropy of gaseous ________ is the largest at 25 °C and 1 atm.

Which reaction produces a decrease in the entropy of the system?

The value of ΔG° at 25 °C for the following reaction: C2H4 (g) + H2 (g) → C2H6 (g) Is ________ kJ/mol. At 298 K, ΔH° for this reaction is -137.5 kJ/mol, and ΔS° is +120.5 J/K.

The value of ΔH° for the decomposition of gaseous sulfur trioxide to its component elements, 2SO3 (g) → 2S (s, rhombic) + 3O2 (g) Is ________ kJ/mol.

Which one of the following is always positive when a spontaneous process occurs?

The equilibrium constant for the following reaction is 3.0 × 108 at 25 °C. N2 (g) + 3H2 (g) 2NH3 (g) The value of ΔG° for this reaction is ________ kJ/mol.

Consider the reaction: NH3 (g) + HCl (g) → NH4Cl (s) Given the following table of thermodynamic data, determine the temperature (in °C)above which the reaction is nonspontaneous.

Of the following, only ________ is not a state function.

When a system is at equilibrium, ________.

Which of the following statements is false?

Phosphorous and chlorine gases combine to produce phosphorous trichloride: P2 (g) + 3Cl2 (g) → 2PCl3 (g) ΔG° at 298 K for this reaction is -642.9 kJ/mol. The value of ΔG at 298 K for a reaction mixture that consists of 1.9 atm P2, 1.6 atm Cl2, and 0.65 atm PCl3 is ________.

The value of ΔS° for the formation of phosphorous trichloride from its constituent elements, P2 (g) + 3Cl2 (g) → 2PCl3 (g) Is ________ J/K ∙ mol.

For a given reaction, ΔH = +22.2 kJ/mol and ΔS = +81.1 J/K-mol. The reaction is spontaneous ________. Assume that ΔH and ΔS do not vary with temperature.

The combustion of ethane in the presence of excess oxygen yields carbon dioxide and water: 2C2H6 (g) + 7O2 (g) → 4CO2 (g) + 6H2O (l) The value of ΔS° for this reaction is ________ J/K ∙ mol.

Which reaction produces an increase in the entropy of the system?

A reversible change produces the maximum amount of ________ that can be achieved by the system on the surroundings.

Consider the reaction: Ag+ (aq) + Cl- (aq) → AgCl (s) Given the following table of thermodynamic data, determine the temperature (in °C)above which the reaction is nonspontaneous under standard conditions.

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Calculate ΔG°(in kJ/mol)for the following reaction at 1 atm and 25 °C: C₂H₆ (g)+ O₂ (g)→ CO₂ (g)+ H₂O (l) (unbalanced) ΔG_f° C₂H₆ (g)= -32.89 kJ/mol; ΔG_f°CO₂ (g)= -394.4 kJ/mol; ΔG_f° H₂O (l)= -237.13 kJ/mol

The value of ΔG° at 25 °C for the following reaction: C₂H₄ (g) + H₂ (g) → C₂H₆ (g) Is ________ kJ/mol. At 298 K, ΔH° for this reaction is -137.5 kJ/mol, and ΔS° is +120.5 J/K.

The value of ΔH° for the decomposition of gaseous sulfur trioxide to its component elements, 2SO₃ (g) → 2S (s, rhombic) + 3O₂ (g) Is ________ kJ/mol.

The equilibrium constant for the following reaction is 3.0 × 10⁸ at 25 °C. N₂ (g) + 3H₂ (g) 2NH₃ (g) The value of ΔG° for this reaction is ________ kJ/mol.

Consider the reaction: NH₃ (g) + HCl (g) → NH₄Cl (s) Given the following table of thermodynamic data, determine the temperature (in °C)above which the reaction is nonspontaneous.

Phosphorous and chlorine gases combine to produce phosphorous trichloride: P₂ (g) + 3Cl₂ (g) → 2PCl₃ (g) ΔG° at 298 K for this reaction is -642.9 kJ/mol. The value of ΔG at 298 K for a reaction mixture that consists of 1.9 atm P₂, 1.6 atm Cl₂, and 0.65 atm PCl₃ is ________.

The value of ΔS° for the formation of phosphorous trichloride from its constituent elements, P₂ (g) + 3Cl₂ (g) → 2PCl₃ (g) Is ________ J/K ∙ mol.

The combustion of ethane in the presence of excess oxygen yields carbon dioxide and water: 2C₂H₆ (g) + 7O₂ (g) → 4CO₂ (g) + 6H₂O (l) The value of ΔS° for this reaction is ________ J/K ∙ mol.

Consider the reaction: Ag⁺ (aq) + Cl^- (aq) → AgCl (s) Given the following table of thermodynamic data, determine the temperature (in °C)above which the reaction is nonspontaneous under standard conditions.