Question 1

Which of the following should have the greatest molar entropy at 298 K?

Accepted Answer

A)  CH4(g) 
B)  H2O(l) 
C)  NaCl(s) 
D)  N2O4(g) 
E)  H2(g) 
A)  CH4(g) 
B)  H2O(l) 
C)  NaCl(s) 
D)  N2O4(g) 
E)  H2(g) D

Question 2

The reaction of methane with water to form carbon dioxide and hydrogen is nonspontaneous at 298 K. At what temperature will this system make the transition from nonspontaneous to spontaneous? The data refer to 298 K. CH4(g) + 2H2O(g)   CO2(g) + 4H2(g)

Accepted Answer

A)  658 K 
B)  683 K 
C)  955 K 
D)  1047 K 
E)  1229 K 
A)  658 K 
B)  683 K 
C)  955 K 
D)  1047 K 
E)  1229 K C

Question 3

Which relationship or statement best describes ΔS° for the following reaction? 2NH3(g) + 2ClF3(g) → 6HF(g) + N2(g) + Cl2(g)

Accepted Answer

A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction. 
A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction. C

Question 4

Which relationship or statement best describes ΔS° for the following reaction? CaO(s) + CO2(g) → CaCO3(s)

Accepted Answer

A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction. 
A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction.

Question 5

A reaction has ΔG = 10.0 kJ and ΔG° = 15.0 kJ at a temperature of 50°C. Calculate the value of the reaction quotient Q under these conditions.

Accepted Answer

A)  0.16 
B)  9.1 × 10-5 
C)  1.1 × 104 
D)  6.4 
E)  6.0 × 10-6 
A)  0.16 
B)  9.1 × 10-5 
C)  1.1 × 104 
D)  6.4 
E)  6.0 × 10-6

Question 6

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl3(g) + 1.5H2(g) → B(s) + 3HCl(g)
Substance: BCl3(g) H2(g) B(s) HCl(g)
S°(J/K·mol): ? 130.6 5.87 186.8
If ΔS° = 80.3 J/K for the reaction above, what is S° for BCl3(g)?

Accepted Answer

A)  -18.2 J/K·mol 
B)  18.2 J/K·mol 
C)  290.1 J/K·mol 
D)  355.4 J/K.mol 
E)  450.6 J/K·mol 
A)  -18.2 J/K·mol 
B)  18.2 J/K·mol 
C)  290.1 J/K·mol 
D)  355.4 J/K.mol 
E)  450.6 J/K·mol

Question 7

Given: H2O(l) → H2O(s) ΔH° = -6.02 kJ at 273K Calculate the entropy change of the surroundings (ΔSsurr) when one mole of water freezes at 0°C and a pressure of one atmosphere.

Accepted Answer

A)  22.1 J/K 
B)  -22.1 J/K 
C)  397 J/K 
D)  -397 J/K 
E)  0.022 J/K 
A)  22.1 J/K 
B)  -22.1 J/K 
C)  397 J/K 
D)  -397 J/K 
E)  0.022 J/K

Question 8

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H3PO4(s)   H3PO4(l)
Use the following thermodynamic information at 298 K to determine this temperature.

Accepted Answer

A)  286 K 
B)  305 K 
C)  315 K 
D)  347 K 
E)  3170 K 
A)  286 K 
B)  305 K 
C)  315 K 
D)  347 K 
E)  3170 K

Question 9

Which relationship or statement best describes ΔS° for the following reaction? Pb(s) + Cl2(g) → PbCl2(s)

Accepted Answer

A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction. 
A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction.

Question 10

Which relationship or statement best describes ΔS° for the following reaction? BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)

Accepted Answer

A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = H°/T 
E)  More information is needed to make a reasonable prediction. 
A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = H°/T 
E)  More information is needed to make a reasonable prediction.

Question 11

Calculate ΔG° for the combustion of propane. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
Substance: C3H8(g) O2(g) CO2(g) H2O(g)
ΔG°f (kJ/mol): -24.5 0 -394.4 -228.6

Accepted Answer

A)  -2073.1 kJ 
B)  -1387.3 kJ 
C)  -598.5 kJ 
D)  598.5 kJ 
E)  2073.1 kJ 
A)  -2073.1 kJ 
B)  -1387.3 kJ 
C)  -598.5 kJ 
D)  598.5 kJ 
E)  2073.1 kJ

Question 12

Under a given set of conditions, all microstates of a system are equally probable.

Accepted Answer

A) True 
 B)False

Question 13

For a chemical reaction to be spontaneous only at high temperatures, which of the following conditions must be met?

Accepted Answer

A)  ΔS° > 0, ΔH° > 0 
B)  ΔS° > 0, ΔH°  0 
E)  ΔG° > 0 
A)  ΔS° > 0, ΔH° > 0 
B)  ΔS° > 0, ΔH°  0 
E)  ΔG° > 0

Question 14

Iron(III) oxide can be reduced by carbon monoxide. Fe2O3(s) + 3CO(g)   2Fe(s) + 3CO2(g)
Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature.

Accepted Answer

A)  7.0 × 10-6 
B)  1.3 × 10-3 
C)  2.2 × 104 
D)  1.4 × 105 
E)  > 2.0 × 105 
A)  7.0 × 10-6 
B)  1.3 × 10-3 
C)  2.2 × 104 
D)  1.4 × 105 
E)  > 2.0 × 105

Question 15

As a chemical reaction proceeds toward equilibrium, the free energy of the system decreases.

Accepted Answer

A) True 
 B)False

Question 16

In order for a process to be spontaneous,

Accepted Answer

A)  ΔH must be less than zero. 
B)  ΔS must be greater than zero. 
C)  ΔG must be greater than zero. 
D)  it should be rapid. 
E)  ΔSsys + ΔSsurr must be greater than zero. 
A)  ΔH must be less than zero. 
B)  ΔS must be greater than zero. 
C)  ΔG must be greater than zero. 
D)  it should be rapid. 
E)  ΔSsys + ΔSsurr must be greater than zero.

Question 17

Which relationship or statement best describes ΔS° for the following reaction? C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)

Accepted Answer

A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction. 
A)  ΔS° ≈ 0 
B)  ΔS°  0 
D)  ΔS° = ΔH°/T 
E)  More information is needed to make a reasonable prediction.

Question 18

Sulfuryl dichloride is formed when sulfur dioxide reacts with chlorine. The data refer to 298 K. SO2(g) + Cl2(g) → SO2Cl2(g)
Substance: SO2(g) Cl2(g) SO2Cl2(g)
ΔH°f (kJ/mol): -296.8 0 -364.0
ΔG°f (kJ/mol): -300.1 0 -320.0
S°(J/K·mol): 248.2 223.0 311.9
What is the value of ΔG° for this reaction at 600 K?

Accepted Answer

A)  -162.8 kJ 
B)  -40.1 kJ 
C)  -28.4 kJ 
D)  28.4 kJ 
E)  162.8 kJ 
A)  -162.8 kJ 
B)  -40.1 kJ 
C)  -28.4 kJ 
D)  28.4 kJ 
E)  162.8 kJ

Question 19

In order for a process to be spontaneous,

Accepted Answer

A)  the entropy of the system must increase. 
B)  the entropy of the surroundings must increase. 
C)  the entropy of the universe must decrease. 
D)  the entropy of the surroundings must decrease. 
E)  the entropy change of the surroundings plus the entropy change of the system must be positive. 
A)  the entropy of the system must increase. 
B)  the entropy of the surroundings must increase. 
C)  the entropy of the universe must decrease. 
D)  the entropy of the surroundings must decrease. 
E)  the entropy change of the surroundings plus the entropy change of the system must be positive.

Question 20

You are given pure samples of ammonia, NH3(g), and nitrogen trifluoride, NF3(g). What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

A)  S°ammonia > S°nitrogen trifluoride 
B)  S°ammonia nitrogen trifluoride 
C)  S°ammonia ≈ S°nitrogen trifluoride 
D)  Other conditions need to be specified before a reliable prediction can be made. 
E)  Even if more conditions are specified, a reliable prediction cannot be made. 
A)  S°ammonia > S°nitrogen trifluoride 
B)  S°ammonia nitrogen trifluoride 
C)  S°ammonia ≈ S°nitrogen trifluoride 
D)  Other conditions need to be specified before a reliable prediction can be made. 
E)  Even if more conditions are specified, a reliable prediction cannot be made.

Exam 20: Thermodynamics Entropy, Free Energy, and Reaction Direction

Which of the following should have the greatest molar entropy at 298 K?

The reaction of methane with water to form carbon dioxide and hydrogen is nonspontaneous at 298 K. At what temperature will this system make the transition from nonspontaneous to spontaneous? The data refer to 298 K. CH4(g) + 2H2O(g) CO2(g) + 4H2(g)

Which relationship or statement best describes ΔS° for the following reaction? 2NH3(g) + 2ClF3(g) → 6HF(g) + N2(g) + Cl2(g)

Which relationship or statement best describes ΔS° for the following reaction? CaO(s) + CO2(g) → CaCO3(s)

A reaction has ΔG = 10.0 kJ and ΔG° = 15.0 kJ at a temperature of 50°C. Calculate the value of the reaction quotient Q under these conditions.

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl3(g) + 1.5H2(g) → B(s) + 3HCl(g) Substance: BCl3(g) H2(g) B(s) HCl(g) S°(J/K·mol): ? 130.6 5.87 186.8 If ΔS° = 80.3 J/K for the reaction above, what is S° for BCl3(g)?

Given: H2O(l) → H2O(s) ΔH° = -6.02 kJ at 273K Calculate the entropy change of the surroundings (ΔSsurr) when one mole of water freezes at 0°C and a pressure of one atmosphere.

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H3PO4(s) H3PO4(l) Use the following thermodynamic information at 298 K to determine this temperature.

Which relationship or statement best describes ΔS° for the following reaction? Pb(s) + Cl2(g) → PbCl2(s)

Which relationship or statement best describes ΔS° for the following reaction? BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)

Calculate ΔG° for the combustion of propane. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) Substance: C3H8(g) O2(g) CO2(g) H2O(g) ΔG°f (kJ/mol): -24.5 0 -394.4 -228.6

Under a given set of conditions, all microstates of a system are equally probable.

For a chemical reaction to be spontaneous only at high temperatures, which of the following conditions must be met?

Iron(III) oxide can be reduced by carbon monoxide. Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g) Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature.

As a chemical reaction proceeds toward equilibrium, the free energy of the system decreases.

In order for a process to be spontaneous,

Which relationship or statement best describes ΔS° for the following reaction? C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)

In order for a process to be spontaneous,

You are given pure samples of ammonia, NH3(g), and nitrogen trifluoride, NF3(g). What prediction would you make concerning their standard molar entropies at 298 K?

Keys to Studying Chemistry Definitions, Units, and Problem Solving

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces Liquids, Solids, and Phase Changes

The Properties of Mixtures Solutions and Colloids

Periodic Patterns in the Main-Group Elements

Organic Compounds and the Atomic Properties of Carbon

Kinetics Rates and Mechanisms of Chemical Reactions

Equilibrium the Extent of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Electrochemistry Chemical Change and Electrical Work

The Elements in Nature and Industry

Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

The reaction of methane with water to form carbon dioxide and hydrogen is nonspontaneous at 298 K. At what temperature will this system make the transition from nonspontaneous to spontaneous? The data refer to 298 K. CH₄(g) + 2H₂O(g) CO₂(g) + 4H₂(g)

Which relationship or statement best describes ΔS° for the following reaction? 2NH₃(g) + 2ClF₃(g) → 6HF(g) + N₂(g) + Cl₂(g)

Which relationship or statement best describes ΔS° for the following reaction? CaO(s) + CO₂(g) → CaCO₃(s)

Elemental boron can be formed by reaction of boron trichloride with hydrogen. BCl₃(g) + 1.5H₂(g) → B(s) + 3HCl(g) Substance: BCl₃(g) H₂(g) B(s) HCl(g) S°(J/K·mol): ? 130.6 5.87 186.8 If ΔS° = 80.3 J/K for the reaction above, what is S° for BCl₃(g)?

Given: H₂O(l) → H₂O(s) ΔH° = -6.02 kJ at 273K Calculate the entropy change of the surroundings (ΔS_surr) when one mole of water freezes at 0°C and a pressure of one atmosphere.

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H₃PO₄(s) H₃PO₄(l) Use the following thermodynamic information at 298 K to determine this temperature.

Which relationship or statement best describes ΔS° for the following reaction? Pb(s) + Cl₂(g) → PbCl₂(s)

Which relationship or statement best describes ΔS° for the following reaction? BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)

Calculate ΔG° for the combustion of propane. C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g) Substance: C₃H₈(g) O₂(g) CO₂(g) H₂O(g) ΔG°_f (kJ/mol): -24.5 0 -394.4 -228.6

Iron(III) oxide can be reduced by carbon monoxide. Fe₂O₃(s) + 3CO(g) 2Fe(s) + 3CO₂(g) Use the following thermodynamic data at 298 K to determine the equilibrium constant at this temperature.

Which relationship or statement best describes ΔS° for the following reaction? C₂H₅OH(l) + 3O₂(g) → 2CO₂(g) + 3H₂O(l)

You are given pure samples of ammonia, NH₃(g), and nitrogen trifluoride, NF₃(g). What prediction would you make concerning their standard molar entropies at 298 K?