Chemistry: The Central Science, 12e (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)
( ) ( )
o o o
rxn f f
ΔH = nΔH products mΔH reactants−
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 degree of disorder 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)
( ) ( )
o o o
rxn f f
ΔH = nΔH products mΔH 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 in the entropy of the system?
A) boiling water to form steam
B) dissolution of solid KCl in water
C) mixing of two gases into one container
D) freezing water to form ice
E) melting ice to form water
14) 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
15) 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
16) 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 =
k
W
C) S =
W
k
D) S = klnW
E) S = Wk
17) 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
18) 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)
19) ΔS is positive for the reaction __________.
A) 2NO (g) + O2 (g) → 2NO2 (g)
B) 2N2 (g) + 3H2 (g) → 2 NH3 (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)
20) 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)
21) 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) Pb+2 (aq) + 2Cl– (aq) → PbCl2 (s)
E) CO2 (g) → CO2 (s)
22) 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)
23) 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) + 1/2Cl2 (g) → NaCl (s)
C) 2 HgO (s) → 2 Hg (l) + O2 (g)
D) U (s) + 3F2 (g) → UF6 (s)
E) H2O (s) → H2O (g)
24) 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) → 2HCl (g)
D) N2 (g) + 3H2 (g) → 2NH3 (g)
E) H2O (l) → H2O (s)
25) 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)
26) 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)
27) ΔS is negative for the reaction __________.
A) 2H2O (g) → 2H2 (g) + O2 (g)
B) Mg(NO3)2 (aq) + 2NaOH(aq) → Mg(OH)2 (s) + 2NaNO3 (aq)
C) H2O (l) → H2O (g)
D) C6H12O6 (s) → 6C (s) + 6H2 (g) + 3O2 (g)
E) NaCl (aq) → Na+ (aq) + Cl– (aq)
28) Of the following, the entropy of __________ is the largest.
A) HCl (l)
B) HCl (s)
C) HCl (g)
D) HBr (g)
E) HI (g)
29) Of the following, the entropy of __________ is the largest.
A) H2O (s)
B) H2O (l)
C) H2O (g)
D) H2S (g)
E) H2S (l)
30) Of the following, the entropy of gaseous __________ is the largest at 25°C and 1 atm.
A) H2
B) C2H6
C) C2H2
D) CH4
E) C2H4
31) Of the following, the entropy of gaseous __________ is the largest at 25°C and 1 atm.
A) CH3OH
B) C2H5OH
C) C3H7OH
D) CH4
E) C4H10
32) 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
33) 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
34) 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
35) For the reaction
2C4H10 (g) + 13O2 (g) → 8CO2 (g) + 10H2O (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
36) 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
37) For a reaction to be spontaneous under standard conditions at all temperatures, the signs of ΔH° and
ΔS° must be __________ and __________, respectively.
A) +, +
B) +, –
C) -, +
D) -, –
E) +, 0
38) Given the following table of thermodynamic data,
complete the following sentence. The vaporization of PCl3 (l) is __________.
A) nonspontaneous at low temperature and spontaneous at high temperature
B) spontaneous at low temperature and nonspontaneous at high temperature
C) spontaneous at all temperatures
D) nonspontaneous at all temperatures
E) not enough information given to draw a conclusion
39) 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
40) 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
41) 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
42) 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
43) 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
44) If ΔG° for a reaction is greater than zero, then __________.
A) K = 0
B) K = 1
C) K > 1
D) K < 1
E) More information is needed.
45) 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