Question 1

The entropy change accompanying any process is given by the equation:

Accepted Answer

A) ΔS = k lnWfinal 
B) ΔS = k Wfinal - k Winitial 
C) ΔS = k ln(Wfinal / Winitial) 
D) ΔS = k final - k initial 
E) ΔS = Wfinal - Winitial 
A) ΔS = k lnWfinal 
B) ΔS = k Wfinal - k Winitial 
C) ΔS = k ln(Wfinal / Winitial) 
D) ΔS = k final - k initial 
E) ΔS = Wfinal - Winitial

Question 2

For a reaction to be spontaneous at low temperature, the signs of ΔH° and ΔS° must be ________ and ________, respectively.

Accepted Answer

A) -, - 
B) +, + 
C) -, + 
D) +, - 
E) +, 0 
A) -, - 
B) +, + 
C) -, + 
D) +, - 
E) +, 0

Question 3

The value of ΔG° for a reaction conducted at 25 °C is 3.05 kJ/mol. The equilibrium constant for a reaction is ________ at this temperature.

Accepted Answer

A) 0.292 
B) -4.20 
C) 0.320 
D) -1.13 
E) More information is needed. 
A) 0.292 
B) -4.20 
C) 0.320 
D) -1.13 
E) More information is needed.

Question 4

The normal boiling point of C2Cl3F3 is 47.6 °C and its molar enthalpy of vaporization is 27.49 kJ/mol. What is the change in entropy in the system in J/K when 28.6 grams of C2Cl3F3 vaporizes to a gas at the normal boiling point?

Accepted Answer

A) -13.1 
B) -4.19 
C) 4.19 
D) 13.1 
E) 27.5 
A) -13.1 
B) -4.19 
C) 4.19 
D) 13.1 
E) 27.5

Question 5

The normal boiling point of methanol is 64.7 °C and the molar enthalpy of vaporization if 71.8 kJ/mol. The value of ΔS when 1.75 mol of CH3OH (l)vaporizes at 64.7 °C is ________ J/K.

Accepted Answer

A) 0.372 
B) 4.24 × 107 
C) 372 
D) 1.94 × 103 
E) 1.94 
A) 0.372 
B) 4.24 × 107 
C) 372 
D) 1.94 × 103 
E) 1.94

Question 6

The first law of thermodynamics can be given as ________.

Accepted Answer

A) ΔE = q + w 
B) Δ   =   -   
C) for any spontaneous process, the entropy of the universe increases 
D) the entropy of a pure crystalline substance at absolute zero is zero 
E) ΔS = qrev/T at constant temperature 
A) ΔE = q + w 
B) Δ   =   -   
C) for any spontaneous process, the entropy of the universe increases 
D) the entropy of a pure crystalline substance at absolute zero is zero 
E) ΔS = qrev/T at constant temperature

Question 7

The value of ΔG° at 261.0 °C for the formation of phosphorous trichloride from its constituent elements, P2 (g)+ 3Cl2 (g) → 2PCl3 (g)
Is ________ kJ/mol. At 25.0 °C for this reaction, ΔH° is -720.5 kJ/mol, ΔG° is -642.9 kJ/mol, and ΔS° is -263.7 J/K.

Accepted Answer

A) -579.6 
B) 6.81 × 104 
C) 1.40 × 105 
D) -651.7 
E) -861.4 
A) -579.6 
B) 6.81 × 104 
C) 1.40 × 105 
D) -651.7 
E) -861.4

Question 8

The standard Gibbs free energy of formation of ________ is zero. (a) H2O (l)
(b) O (g)
(c) Cl2 (g)

Accepted Answer

A) (a)only 
B) (b)only 
C) (c)only 
D) (b)and (c) 
E) (a), (b), and (c) 
A) (a)only 
B) (b)only 
C) (c)only 
D) (b)and (c) 
E) (a), (b), and (c)

Question 9

The value of ΔS° for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic)+ O2(g) → SO2(g)
Is ________ J/K ∙ mol.

Accepted Answer

A) +485.4 
B) +248.5 
C) -11.6 
D) -248.5 
E) +11.6 
A) +485.4 
B) +248.5 
C) -11.6 
D) -248.5 
E) +11.6

Question 10

The value of ΔS° for the decomposition of POCl3 into its constituent elements, 2POCl3 (g) → P2 (g) + O2 (g) + 3Cl2 (g)
Is ________ J/K ∙ mol.

Accepted Answer

A) +771.0 
B) +442.0 
C) -321.0 
D) -771.0 
E) +321.0 
A) +771.0 
B) +442.0 
C) -321.0 
D) -771.0 
E) +321.0

Question 11

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 value of ΔS° for the catalytic hydrogenation of ethene to ethane, C2H4 (g) + H2(g) → C2H6 (g)
Is ________ J/K ∙ mol.

Accepted Answer

A) -101.9 
B) -120.5 
C) -232.5 
D) +112.0 
E) +101.9 
A) -101.9 
B) -120.5 
C) -232.5 
D) +112.0 
E) +101.9

Question 12

The value of ΔG° at 373 K for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic) + O2 (g) → SO2 (g)
Is ________ kJ/mol. At 298 K, ΔH° for this reaction is -269.9 kJ/mol, and ΔS° is +11.6 J/K.

Accepted Answer

A) -300.4 
B) +300.4 
C) -4,597 
D) +4,597 
E) -274.2 
A) -300.4 
B) +300.4 
C) -4,597 
D) +4,597 
E) -274.2

Question 13

The value of ΔH° for the decomposition of gaseous sulfur dioxide to solid elemental sulfur and gaseous oxygen, SO2 (g) → S (s,rhombic) + O2 (g)
Is ________ kJ/mol.

Accepted Answer

A) 0.0 
B) +135.0 
C) -135.90 
D) -269.9 
E) +269.9 
A) 0.0 
B) +135.0 
C) -135.90 
D) -269.9 
E) +269.9

Question 14

Consider the reaction: NH3 (g) + HCl (g) → NH4Cl (s)
Given the following table of thermodynamic data at 298 K:   The value of K for the reaction at 25 °C is ________.

Accepted Answer

A) 150 
B) 9.3 × 1015 
C) 8.4 × 104 
D) 1.1 × 10-16 
E) 1.4 × 108 
A) 150 
B) 9.3 × 1015 
C) 8.4 × 104 
D) 1.1 × 10-16 
E) 1.4 × 108

Question 15

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

Accepted Answer

A) -288.1 
B) +432.4 
C) -720.5 
D) +720.5 
E) -432.4 
A) -288.1 
B) +432.4 
C) -720.5 
D) +720.5 
E) -432.4

Question 16

The value of ΔG° at 25 °C for the decomposition of gaseous sulfur trioxide to solid elemental sulfur and gaseous oxygen, 2SO3 (g) → 2S (s, rhombic) + 3O2 (g)
Is ________ kJ/mol.

Accepted Answer

A) +740.8 
B) -370.4 
C) +370.4 
D) -740.8 
E) +185.2 
A) +740.8 
B) -370.4 
C) +370.4 
D) -740.8 
E) +185.2

Question 17

Consider the reaction: FeO (s) + Fe (s) + O2 (g) → Fe2O3 (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) 756.3 
D) 2438 
E) 1235 
A) This reaction is spontaneous at all temperatures. 
B) 618.1 
C) 756.3 
D) 2438 
E) 1235

Question 18

Of the following, the entropy of ________ is the largest.

Accepted Answer

A) HI (g) 
B) HBr (g) 
C) HCl (g) 
D) HCl (s) 
E) HCl (l) 
A) HI (g) 
B) HBr (g) 
C) HCl (g) 
D) HCl (s) 
E) HCl (l)

Question 19

The value of ΔG° at 25 °C for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic) + O2(g) → SO2 (g)
Is ________ kJ/mol.

Accepted Answer

A) +395.2 
B) +269.9 
C) -269.9 
D) +300.4 
E) -300.4 
A) +395.2 
B) +269.9 
C) -269.9 
D) +300.4 
E) -300.4

Question 20

Which one of the following correctly indicates the relationship between the entropy of a system and the number of different arrangements, W, in the system?

Accepted Answer

A) S = kW 
B) S =   
C) S =   
D) S = k lnW 
E) S = Wk 
A) S = kW 
B) S =   
C) S =   
D) S = k lnW 
E) S = Wk

Exam 19: Chemical Thermodynamics

The entropy change accompanying any process is given by the equation:

For a reaction to be spontaneous at low temperature, the signs of ΔH° and ΔS° must be ________ and ________, respectively.

The value of ΔG° for a reaction conducted at 25 °C is 3.05 kJ/mol. The equilibrium constant for a reaction is ________ at this temperature.

The normal boiling point of C2Cl3F3 is 47.6 °C and its molar enthalpy of vaporization is 27.49 kJ/mol. What is the change in entropy in the system in J/K when 28.6 grams of C2Cl3F3 vaporizes to a gas at the normal boiling point?

The normal boiling point of methanol is 64.7 °C and the molar enthalpy of vaporization if 71.8 kJ/mol. The value of ΔS when 1.75 mol of CH3OH (l)vaporizes at 64.7 °C is ________ J/K.

The first law of thermodynamics can be given as ________.

The value of ΔG° at 261.0 °C for the formation of phosphorous trichloride from its constituent elements, P2 (g)+ 3Cl2 (g) → 2PCl3 (g) Is ________ kJ/mol. At 25.0 °C for this reaction, ΔH° is -720.5 kJ/mol, ΔG° is -642.9 kJ/mol, and ΔS° is -263.7 J/K.

The standard Gibbs free energy of formation of ________ is zero. (a) H2O (l) (b) O (g) (c) Cl2 (g)

The value of ΔS° for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic)+ O2(g) → SO2(g) Is ________ J/K ∙ mol.

The value of ΔS° for the decomposition of POCl3 into its constituent elements, 2POCl3 (g) → P2 (g) + O2 (g) + 3Cl2 (g) Is ________ J/K ∙ mol.

The value of ΔG° at 373 K for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic) + O2 (g) → SO2 (g) Is ________ kJ/mol. At 298 K, ΔH° for this reaction is -269.9 kJ/mol, and ΔS° is +11.6 J/K.

The value of ΔH° for the decomposition of gaseous sulfur dioxide to solid elemental sulfur and gaseous oxygen, SO2 (g) → S (s,rhombic) + O2 (g) Is ________ kJ/mol.

Consider the reaction: NH3 (g) + HCl (g) → NH4Cl (s) Given the following table of thermodynamic data at 298 K: The value of K for the reaction at 25 °C is ________.

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

The value of ΔG° at 25 °C for the decomposition of gaseous sulfur trioxide to solid elemental sulfur and gaseous oxygen, 2SO3 (g) → 2S (s, rhombic) + 3O2 (g) Is ________ kJ/mol.

Consider the reaction: FeO (s) + Fe (s) + O2 (g) → Fe2O3 (s) Given the following table of thermodynamic data, determine the temperature (in °C)above which the reaction is nonspontaneous.

Of the following, the entropy of ________ is the largest.

The value of ΔG° at 25 °C for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic) + O2(g) → SO2 (g) Is ________ kJ/mol.

Which one of the following correctly indicates the relationship between the entropy of a system and the number of different arrangements, W, in the system?

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For a reaction to be spontaneous at low temperature, the signs of ΔH° and ΔS° must be and , respectively.

The normal boiling point of C₂Cl₃F₃ is 47.6 °C and its molar enthalpy of vaporization is 27.49 kJ/mol. What is the change in entropy in the system in J/K when 28.6 grams of C₂Cl₃F₃ vaporizes to a gas at the normal boiling point?

The normal boiling point of methanol is 64.7 °C and the molar enthalpy of vaporization if 71.8 kJ/mol. The value of ΔS when 1.75 mol of CH₃OH (l)vaporizes at 64.7 °C is ________ J/K.

The value of ΔG° at 261.0 °C for the formation of phosphorous trichloride from its constituent elements, P₂ (g)+ 3Cl₂ (g) → 2PCl₃ (g) Is ________ kJ/mol. At 25.0 °C for this reaction, ΔH° is -720.5 kJ/mol, ΔG° is -642.9 kJ/mol, and ΔS° is -263.7 J/K.

The standard Gibbs free energy of formation of ________ is zero. (a) H₂O (l) (b) O (g) (c) Cl₂ (g)

The value of ΔS° for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic)+ O₂(g) → SO₂(g) Is ________ J/K ∙ mol.

The value of ΔS° for the decomposition of POCl₃ into its constituent elements, 2POCl₃ (g) → P₂ (g) + O₂ (g) + 3Cl₂ (g) Is ________ J/K ∙ mol.

The value of ΔG° at 373 K for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic) + O₂ (g) → SO₂ (g) Is ________ kJ/mol. At 298 K, ΔH° for this reaction is -269.9 kJ/mol, and ΔS° is +11.6 J/K.

The value of ΔH° for the decomposition of gaseous sulfur dioxide to solid elemental sulfur and gaseous oxygen, SO₂ (g) → S (s,rhombic) + O₂ (g) Is ________ kJ/mol.

Consider the reaction: NH₃ (g) + HCl (g) → NH₄Cl (s) Given the following table of thermodynamic data at 298 K: The value of K for the reaction at 25 °C is ________.

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

The value of ΔG° at 25 °C for the decomposition of gaseous sulfur trioxide to solid elemental sulfur and gaseous oxygen, 2SO₃ (g) → 2S (s, rhombic) + 3O₂ (g) Is ________ kJ/mol.

Consider the reaction: FeO (s) + Fe (s) + O₂(g) → Fe₂O₃ (s) Given the following table of thermodynamic data, determine the temperature (in °C)above which the reaction is nonspontaneous.

The value of ΔG° at 25 °C for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, S (s, rhombic) + O₂(g) → SO₂ (g) Is ________ kJ/mol.