Chapter 19 1 The first law of thermodynamics can be given as

Chemistry: The Central Science, 13e (Brown et al.)

Chapter 19 Chemical Thermodynamics

19.1 Multiple-Choice Questions

1) The first law of thermodynamics can be given as ________.

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

2) A reaction that is spontaneous as written ________.

A) is very rapid

B) will proceed without outside intervention

C) is also spontaneous in the reverse direction

D) has an equilibrium position that lies far to the left

E) is very slow

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

A) S

B) H

C) q

D) E

E) T

4) When a system is at equilibrium, ________.

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

5) A reversible process is one that ________.

A) can be reversed with no net change in either system or surroundings

B) happens spontaneously

C) is spontaneous in both directions

D) must be carried out at low temperature

E) must be carried out at high temperature

6) Which of the following statements is true?

A) Processes that are spontaneous in one direction are spontaneous in the opposite direction.

B) Processes are spontaneous because they occur at an observable rate.

C) Spontaneity can depend on the temperature.

D) All of the statements are true.

7) The thermodynamic quantity that expresses the extent of randomness in a system is ________.

A) enthalpy

B) internal energy

C) bond energy

D) entropy

E) heat flow

8) For an isothermal process, ΔS = ________.

A) q

B) qrev/T

C) qrev

D) Tqrev

E) q + w

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

A) ΔSsystem

B) ΔSsurroundings

C) ΔSuniverse

D) ΔHuniverse

E) ΔHsurroundings

10) The entropy of the universe is ________.

A) constant

B) continually decreasing

C) continually increasing

D) zero

E) the same as the energy, E

11) The second law of thermodynamics states that ________.

A) ΔE = q + w

B) ΔH°rxn = Σ nΔH°f (products) – Σ mΔH°f (reactants)

C) for any spontaneous process, the entropy of the universe increases

D) the entropy of a pure crystalline substance is zero at absolute zero

E) ΔS = qrev/T at constant temperature

12) Which of the following statements is false?

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.

13) Which one of the following processes produces a decrease of the entropy of the system?

A) dissolving sodium chloride in water

B) sublimation of naphthalene

C) dissolving oxygen in water

D) boiling of alcohol

E) explosion of nitroglycerine

14) Consider a pure crystalline solid that is heated from absolute zero to a temperature above the boiling

point of the liquid. Which of the following processes produces the greatest increase in the entropy of the

substance?

A) melting the solid

B) heating the liquid

C) heating the gas

D) heating the solid

E) vaporizing the liquid

15) 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?

A) S = kW

B) S =

C) S =

D) S = k lnW

E) S = Wk

5

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

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

17) ΔS is positive for the reaction ________.

A) 2H2 (g) + O2 (g) → 2H2O (g)

B) 2NO2 (g) → N2O4 (g)

C) CO2 (g) → CO2 (s)

D) BaF2 (s) → Ba2+ (aq) + 2F– (aq)

E) 2Hg (l) + O2 (g) → 2HgO (s)

18) ΔS is positive for the reaction ________.

A) 2NO (g) + O2 (g) → 2NO2 (g)

B) 2N2 (g) + 3H2 (g) → 2NH3 (g)

C) C3H8 (g) + 5 O2 (g) → 3CO2 (g) + 4 H2O (g)

D) Mg (s) + Cl2 (g) → MgCl2 (s)

E) C2H4 (g) + H2 (g) → C2H6 (g)

19) ΔS is positive for the reaction ________.

A) CaO (s) + CO2 (g) → CaCO3 (s)

B) N2 (g) + 3H2 (g) → 2NH3 (g)

C) 2SO3 (g) → 2SO2 (g) + O2 (g)

D) Ag+ (aq) + Cl– (aq) → AgCl (s)

E) H2O (l) → H2O (s)

20) ΔS is positive for the reaction ________.

A) 2 Ca (s) + O2 (g) → 2 CaO (s)

B) 2 KClO3 (s) → 2KCl (s) + 3 O2 (g)

C) HCl (g) + NH3 (g) → NH4Cl (s)

D) Pb2+ (aq) + 2Cl– (aq) → PbCl2 (s)

E) CO2 (g) → CO2 (s)

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

A) CaCO3 (s) → CaO (s) + CO2 (g)

B) 2C (s) + O2 (g) → 2CO (g)

C) CO2 (s) → CO2 (g)

D) 2H2 (g) + O2 (g) → 2H2O (l)

E) H2O (l) → H2O (g)

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

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)

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

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)

24) ΔS is negative for the reaction ________.

A) 2SO2 (g) + O2 (g) → 2SO3 (g)

B) NH4Cl (s) → NH3 (g) + HCl (g)

C) PbCl2 (s) → Pb2+ (aq) + 2Cl– (aq)

D) 2C (s) + O2 (g) → 2CO2 (g)

E) H2O (l) → H2O (g)

25) ΔS is positive for the reaction ________.

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)

26) For an isothermal process, the entropy change of the surroundings is given by the equation:

A) ΔS = qsys T

B) ΔS = -qsys T

C) ΔS = q lnT

D) ΔS = -q lnT

E) ΔS = -qsys / T

27) The equilibrium position corresponds to which letter on the graph of G vs. f (course of reaction)

below?

A) A

B) B

C) C

D) D

E) E

28) For the reaction

C2H6 (g) → C2H4 (g) + H2 (g)

ΔH° is +137 kJ/mol and ΔS° is +120 J/K ∙ mol. This reaction is ________.

A) spontaneous at all temperatures

B) spontaneous only at high temperature

C) spontaneous only at low temperature

D) nonspontaneous at all temperatures

29) For the reaction

2 C4H10 (g) + 13 O2 (g) → 8 CO2 (g) + 10 H2O (g)

ΔH° is –125 kJ/mol and ΔS° is +253 J/K ∙ mol. This reaction is ________.

A) spontaneous at all temperatures

B) spontaneous only at high temperature

C) spontaneous only at low temperature

D) nonspontaneous at all temperatures

E) unable to determine without more information

30) A reaction that is not spontaneous at low temperature can become spontaneous at high temperature if

ΔH is ________ and ΔS is ________.

A) +, +

B) –, –

C) +, –

D) –, +

E) +, 0

31) Given the following table of thermodynamic data,

complete the following sentence. The vaporization of TiCl4 is ________.

A) spontaneous at all temperatures

B) spontaneous at low temperature and nonspontaneous at high temperature

C) nonspontaneous at low temperature and spontaneous at high temperature

D) nonspontaneous at all temperatures

E) not enough information given to draw a conclusion

32) 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.

A) 1230

B) 150

C) 432

D) 133

E) 1640

33) 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.

A) This reaction is spontaneous at all temperatures.

B) 618.1

C) 432.8

D) 345.0

E) 1235

34) 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.

A) This reaction is spontaneous at all temperatures.

B) 618.1

C) 756.3

D) 2438

E) 1235

35) With thermodynamics, one cannot determine ________.

A) the speed of a reaction

B) the direction of a spontaneous reaction

C) the extent of a reaction

D) the value of the equilibrium constant

E) the temperature at which a reaction will be spontaneous

36) Which one of the following statements is true about the equilibrium constant for a reaction if ΔG° for

the reaction is negative?

A) K = 0

B) K = 1

C) K > 1

D) K < 1

E) More information is needed.

19.2 Bimodal Questions

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

C2H2 (g) 226.7 209.2 200.8

C2H4 (g) 52.30 68.11 219.4

C2H6 (g) -84.68 -32.89 229.5

CO (g) -110.5 -137.2 197.9

CO2 (g) -393.5 -394.4 213.6

Hydrogen

H2( g) 0 0 130.58

Oxygen

O2 (g) 0 0 205.0

H2O (l) -285.83 -237.13 69.91

1) The value of ΔS° for the catalytic hydrogenation of acetylene to ethene,

C2H2 (g) + H2 (g) → C2H4 (g)

is ________ J/K∙ mol.

A) +18.6

B) +550.8

C) +112.0

D) -112.0

E) -18.6

2) 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.

A) +689.3

B) +122.3

C) +432.4

D) -122.3

E) -432.4

3) The value of ΔS° for the reaction

2C (s, diamond) + O2 (g) → 2CO (g)

is ________ J/K ∙ mol.

A) -185.9

B) +185.9

C) -9.5

D) +9.5

E) -195.7

4) The value of ΔS° for the catalytic hydrogenation of ethene to ethane,

C2H4 (g) + H2(g) → C2H6 (g)

is ________ J/K ∙ mol.

A) -101.9

B) -120.5

C) -232.5

D) +112.0

E) +101.9

5) The value of ΔS° for the catalytic hydrogenation of acetylene to ethane,

C2H2 (g) + 2H2 (g) → C2H6 (g)

is ________ J/K ∙ mol.

A) -76.0

B) +440.9

C) -232.5

D) +232.5

E) +28.7

6) The value of ΔS° for the oxidation of carbon to carbon monoxide,

2C (s, graphite) + O2 (g) → 2CO (g)

is ________ J/K ∙ mol. Carbon monoxide is produced in the combustion of carbon with limited oxygen.

A) -12.8

B) +408.6

C) -408.6

D) +179.4

E) +395.8

7) The value of ΔS° for the oxidation of carbon to carbon dioxide,

C (s, graphite) + O2 (g) → CO2(g)

is ________ J/K ∙ mol. The combustion of carbon, as in charcoal briquettes, in the presence of abundant

oxygen produces carbon dioxide.

A) +424.3

B) +205.0

C) -205.0

D) -2.9

E) +2.9

8) The combustion of ethene in the presence of excess oxygen yields carbon dioxide and water:

C2H4 (g) + 3O2 (g) → 2CO2 (g) + 2H2O (l)

The value of ΔS° for this reaction is ________ J/K ∙ mol.

A) -267.4

B) -140.9

C) -347.6

D) +347.6

E) +140.9

9) 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.

A) +718.0

B) -620.1

C) -718.0

D) -151.0

E) +151.0

10) The combustion of hydrogen in the presence of excess oxygen yields water:

2H2(g) + O2(g) → 2H2O (l)

The value of ΔS° for this reaction is ________ J/K ∙ mol.

A) +405.5

B) -405.5

C) -326.3

D) -265.7

E) +265.7

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)

Calcium

Ca (s) 0 0 41.4

CaCl2 (s) -795.8 -748.1 104.6

Ca2+ (aq) 226.7 209.2 200.8

Chlorine

Cl2 (g) 0 0 222.96

Cl– (aq) -167.2 -131.2 56.5

Oxygen

O2 (g) 0 0 205.0

H2O (l) -285.83 -237.13 69.91

Phosphorus

P2 (g) 144.3 103.7 218.1

PCl3 (g) -288.1 -269.6 311.7

POCl3 (g) -542.2 -502.5 325

Sulfur

S (s, rhombic) 0 0 31.88

SO2(g) -269.9 -300.4 248.5

SO3(g) -395.2 -370.4 256.2

11) The value of ΔS° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide,

2S (s, rhombic) + 3O2(g) → 2SO3 (g)

is ________ J/K ∙ mol.

A) +19.3

B) -19.3

C) +493.1

D) -166.4

E) -493.1

12) 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.

A) +485.4

B) +248.5

C) -11.6

D) -248.5

E) +11.6

13) The value of ΔS° for the decomposition of gaseous sulfur trioxide to solid elemental sulfur and

gaseous oxygen,

2SO3 (g) → 2S (s, rhombic) + 3O2 (g)

is ________ J/K ∙ mol.

A) +19.3

B) -19.3

C) +493.1

D) +166.4

E) -493.1

14) The value of ΔS° for the decomposition of gaseous sulfur dioxide to solid elemental sulfur and

gaseous oxygen,

SO2 (g) → S (s, rhombic) + O2 (g)

is ________ J/K ∙ mol.

A) +485.4

B) +248.5

C) -11.6

D) -248.5

E) +11.6

15) The value of ΔS° for the formation of POCl3 from its constituent elements,

P2 (g) + O2 (g) + 3Cl2 (g) → 2POCl3 (g)

is ________ J/K ∙ mol.

A) -442.0

B) +771.0

C) -321.0

D) -771.0

E) +321.0

16) 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.

A) +771.0

B) +442.0

C) -321.0

D) -771.0

E) +321.0

17) The value of ΔS° for the formation of phosphorous trichloride from its constituent elements,

P2 (g) + 3Cl2 (g) → 2PCl3 (g)

is ________ J/K ∙ mol.

A) -311.7

B) +311.7

C) -263.6

D) +129.4

E) -129.4

18) The value of ΔS° for the decomposition of phosphorous trichloride into its constituent elements,

2PCl3 (g) → P2 (g) + 3Cl2( g)

is ________ J/K ∙ mol.

A) -311.7

B) +311.7

C) +263.6

D) +129.4

E) -129.4

19) The value of ΔS° for the formation of calcium chloride from its constituent elements,

Ca (s) + Cl2 (g) → CaCl2 (s)

is ________ J/K ∙ mol.

A) -104.6

B) +104.6

C) +369.0

D) -159.8

E) +159.8

20) The value of ΔS° for the decomposition of calcium chloride into its constituent elements,

CaCl2 (s) → Ca (s) + Cl2 (g)

is ________ J/K ∙ mol.

A) -104.6

B) +104.6

C) +369.0

D) -159.8

E) +159.8

21) The value of ΔH° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide,

2S (s, rhombic) + 3O2( g) → 2SO3 (g)

is ________ kJ/mol.

A) +790.4

B) -790.4

C) +395.2

D) -395.2

E) +105.1

22) 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.

A) +790.4

B) -790.4

C) +395.2

D) -395.2

E) +105.1

23) The value of ΔH° for the oxidation of solid elemental sulfur to gaseous sulfur dioxide,

S (s, rhombic) + O2 (g) → SO2 (g)

is ________ kJ/mol.

A) +269.9

B) -269.9

C) +0.00

D) -11.6

E) +11.6