61) Determine the equilibrium constant for the following reaction at 298 K.
SO3(g) + H2O(g) → H2SO4(l) ΔG° = -90.5 kJ
A) 1.37 × 10-16
B) 4.78 × 1011
C) 9.11 × 10-8
D) 7.31 × 1015
E) 0.964
62) Determine the equilibrium constant for the following reaction at 298 K.
Cl(g) + O3(g) → ClO(g) + O2(g) ΔG° = – 34.5 kJ
A) 5.66 × 105
B) 0.986
C) 8.96 × 10-7
D) 4.98 × 10-4
E) 1.12 × 106
63) Determine the equilibrium constant for the following reaction at 498 K.
2 Hg(g) + O2(g) → 2 HgO(s) ΔH° = –304.2 kJ; ΔS° = -414.2 J/K
A) 1.87 × 1010
B) 8.10 × 1031
C) 2.31 × 10-22
D) 5.34 × 10-11
E) 4.33 × 1021
64) Determine the equilibrium constant for the following reaction at 655 K.
HCN(g) + 2 H2(g) → CH3NH2(g) ΔH° = –158 kJ; ΔS°= -219.9 J/K
A) 3.99 × 1012
B) 13.0
C) 2.51 × 10-13
D) 3.26 × 10-12
E) 3.07 × 1011
65) Determine the equilibrium constant for the following reaction at 549 K.
CH2O(g) + 2 H2(g) → CH4(g) + H2O(g) ΔH° = –94.9 kJ; ΔS°= -224.2 J/K
A) 481
B) 1.07 x 109
C) 2.08 x 10-3
D) 9.35 x 10-10
E) 1.94 x 10-12
Algorithmic Questions
1) In which of the following processes does the molecules become more orderly?
A) water freezing
B) ice melting
C) water evaporating
D) salt dissolving in water
E) dry ice subliming
2) Identify the change in state that does not have an increase in entropy.
A) water freezing
B) water boiling
C) ice melting
D) dry ice subliming
E) rubbing alcohol evaporating
3) Which of the following processes have a ΔS > 0?
A) 2 NH3(g) + CO2(g) → NH2CONH2(aq) + H2O(l)
B) lithium fluoride forms from its elements
C) 2 HF(g) → H2(g) + F2(l)
D) potassium iodide dissolves in pure water
E) All of the above processes have a DS > 0.
4) Which of the following processes have a ΔS < 0?
A) water freezes
B) methyl alcohol condenses
C) propanol (g, at 555 K) → propanol (g, at 400 K)
D) carbon dioxide(g) → carbon dioxide(s)
E) All of the above processes have a ΔS < 0.
5) Which of the following processes shows a decrease in entropy of the system?
A) 2 NO(g) + O2(g) → 2 NO2(g)
B) COBr2(g) → CO(g) + Br2(g)
C) CH3OH(l) → CO(g) + 2H2(g)
D) KBrO3(s) →K+(aq) + BrO3–(aq)
E) None of the above will show a decrease in entropy.
6) Consider the following reaction at constant P. Use the information here to determine the value of
ΔSsurr at 298 K. Predict whether or not this reaction will be spontaneous at this temperature.
N2(g) + 2 O2(g) → 2 NO2(g) ΔH = +66.4 kJ
A) ΔSsurr = +223 J/K, reaction is spontaneous spontaneous
B) ΔSsurr = -223 J/K, reaction is not spontaneous
C) ΔSsurr = -66.4 J/K, reaction is not spontaneous
D) ΔSsurr = +2656 kJ/K, reaction is not spontaneous
E) ΔSsurr = -66.4 J/K, it is not possible to predict the spontaneity of this reaction without more
information.
7) Consider the following reaction at constant P. Use the information here to determine the value of
ΔSsurr at 355 K. Predict whether or not this reaction will be spontaneous at this temperature.
2 NO(g) + O2(g) → 2 NO2(g) ΔH = -114 kJ
A) ΔSsurr = +114 kJ/K, reaction is spontaneous
B) ΔSsurr = +114 kJ/K, reaction is not spontaneous
C) ΔSsurr = +321 J/K, reaction is spontaneous
D) ΔSsurr = -321 J/K, reaction is spontaneous
E) ΔSsurr = +321 J/K, it is not possible to predict the spontaneity of this reaction without more
information.
8) Consider the following reaction at constant P. Use the information here to determine the value of
ΔSsurr at 398 K. Predict whether or not this reaction will be spontaneous at this temperature.
4 NH3(g) + 3 O2(g) → 2 N2(g) + 6 H2O(g) ΔH = -1267 kJ
A) ΔSsurr = +12.67 kJ/K, reaction is spontaneous
B) ΔSsurr = -12.67 kJ/K, reaction is spontaneous
C) ΔSsurr = +50.4 kJ/K, reaction is not spontaneous
D) ΔSsurr = +3.18 kJ/K, reaction is spontaneous
E) ΔSsurr = -3.18 kJ/K, it is not possible to predict the spontaneity of this reaction without more
information.
9) Place the following in order of increasing molar entropy at 298 K.
CO2 C9H20 CO
A) CO2 < C9H20 < CO
B) C9H20 < CO2 < CO
C) CO < CO2 < C9H20
D) C9H20 < CO < CO2
E) CO2 < CO < C9H20
10) Place the following in order of decreasing molar entropy at 298 K.
HF N2H4 Ar
A) Ar > N2H4 > HF
B) Ar > HF > N2H4
C) N2H4 > Ar > HF
D) N2H4 > HF > Ar
E) HF > N2H4 > Ar
11) Place the following in order of decreasing standard molar entropy.
NaF(s) Li3PO4(aq) NaF(aq)
A) NaF(s) > NaF(aq) > Li3PO4(aq)
B) NaF(aq) > NaF(s) > Li3PO4(aq)
C) Li3PO4(aq) > NaF(aq) > NaF(s)
D) NaF(s) > Li3PO4(aq) > NaF(aq)
E) NaF(aq) > Li3PO4(aq) > NaF(s)
12) Which one of the following has the highest standard molar entropy, S°, at 25°C?
A) I2(g)
B) F2(g)
C) Br2(l)
D) O2(g)
E) Cl2(g)
13) Identify the compound that is NOT an allotrope of carbon.
A) diamond
B) ethanol
C) graphite
D) charcoal
E) buckyball
14) Which one of the following would be expected to have the lowest standard molar entropy, S°, at
25°C?
A) C10H22(s)
B) C10H22(l)
C) C14H30(s)
D) C14 H30OH(l)
15) Identify the compound with the lowest standard free energy of formation.
A) NaCl(s)
B) O2(g)
C) NO(g)
D) O3(g)
E) It is hard to determine.
16) Identify the compound with the highest standard free energy of formation.
A) NaCl(s)
B) H2(g)
C) NO(g)
D) O3(g)
E) It is hard to determine.
17) Identify the compound with the standard free energy of formation equal to zero.
A) KBr(s)
B) H2(g)
C) NO(g)
D) O3(g)
E) It is hard to determine.
18) Given the following equation,
H2O(g) + CO(g) → H2(g) + CO2(g) ΔG°rxn = -28.6 kJ
Calculate ΔG°rxn for the following reaction.
5 H2O(g) + 5 CO(g) → 5 H2(g) + 5 CO2(g)
A) -143.0 kJ
B) +143.0 kJ
C) -5.72 kJ
D) +5.72 kJ
E) -28.6 kJ
19) Given the following equation,
H2O(g) + CO(g) → H2(g) + CO2(g) ΔG°rxn = -28.6 kJ
Calculate ΔG°rxn for the following reaction.
5 H2(g) + 5 CO2(g) → 5 H2O(g) + 5 CO(g)
A) -143.0 kJ
B) +143.0 kJ
C) -5.72 kJ
D) +5.72 kJ
E) -28.6 kJ
22
20) Given the following equation,
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g) ΔG°rxn = -2074 kJ
Calculate ΔG°rxn for the following reaction.
7 C3H8(g) + 35 O2(g) → 21 CO2(g) + 28 H2O(g)
A) -2074 kJ
B) +14518 kJ
C) -14518 kJ
D) +2074 kJ
E) -296 kJ
21) Given the following equation,
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(g) ΔG°rxn = -2074 kJ
Calculate ΔG°rxn for the following reaction.
21 CO2(g) + 28 H2O(g) → 7 C3H8(g) + 35 O2 g)
A) -2074 kJ
B) +14518 kJ
C) -14518 kJ
D) +2074 kJ
E) -296 kJ
22) Given the following equation,
N2O(g) + NO2(g) → 3 NO(g) ΔG°rxn = -23.0 kJ
Calculate ΔG°rxn for the following reaction.
6 N2O(g) + 6 NO2(g) → 18 NO(g)
A) -23.0 kJ
B) 138 kJ
C) -138 kJ
D) -3.83 kJ
E) 23.0 kJ
23) Given the following equation,
N2O(g) + NO2(g) → 3 NO(g) ΔG°rxn = -23.0 kJ
Calculate ΔG°rxn for the following reaction.
18 NO(g) → 6 N2O(g) + 6 NO2(g)
A) -23.0 kJ
B) 138 kJ
C) -138 kJ
D) -3.83 kJ
E) 23.0 kJ
24) Estimate ΔG°rxn for the following reaction at 449.0 K.
CH2O(g) + 2 H2(g) → CH4(g) + H2O(g) ΔH°= –94.9 kJ; ΔS°= -224.2 J/K
A) +5.8 kJ
B) +12.9 kJ
C) +101 kJ
D) +2.4 kJ
E) -4.2 kJ
25) Estimate ΔG°rxn for the following reaction at 417 K.
HCN(g) + 2 H2(g) → CH3NH2(g) ΔH°= –158.0 kJ; ΔS°= -219.9 J/K
A) +61.9 kJ
B) -66.3 kJ
C) +66.3 kJ
D) -250 kJ
E) +250 kJ
24
26) Estimate ΔG°rxn for the following reaction at 825 K.
2 Hg(g) + O2(g) → 2 HgO(s) ΔH°= –304.2 kJ; ΔS°= -414.2 J/K
A) -2.63 kJ
B) -37 kJ
C) +37 kJ
D) +645 kJ
E) -645 kJ
27) Determine ΔG°rxn for the following reaction at 338 K.
FeO(s) + CO(g) → Fe(s) + CO2(g) ΔH°= –11.0 kJ; ΔS°= -17.4 J/K
A) +191.0 kJ
B) -5.1 kJ
C) +5.1 kJ
D) -16.1 kJ
E) +16.1 kJ
28) Determine ΔG°rxn for the following reaction at 358 K.
CaCO3(s) → CaO(s) + CO2(g) ΔH°= +179.2 kJ; DS°= +160.2 J/K
A) +179.2 kJ
B) +236.6 kJ
C) -236.6 kJ
D) +121.8 kJ
E) -121.8 kJ
29) Calculate the ΔG°rxn using the following information.
2 H2S(g) + 3 O2(g) → 2 SO2(g) + 2 H2O(g) ΔG°rxn = ?
ΔG°f (kJ/mol) -33.4 -300.1 -228.6
A) +990.6 kJ
B) -495.3 kJ
C) +528.7 kJ
D) +66.8 kJ
E) -990.6 kJ
30) The value of ΔG° at 141.0°C for the formation of phosphorous trichloride from its constituent
25
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.
A) -612.3
B) 3.65 × 104
C) 1.08 × 105
D) -683.3
E) -829.7
31) The value of ΔG° at 100.0°C for the formation of calcium chloride from its constituent elements:
Ca(s) + Cl2(g) → CaCl2 (s)
is ________ kJ/mol. At 25.0°C for this reaction, ΔH° is –795.8 kJ/mol, ΔG° is –748.1 kJ/mol, and ΔS° is
-159.8 J/K.
A) -855.4
B) -736.1
C) 5.88 × 104
D) -779.8
E) 1.52 × 104
32) For a given reaction, ΔH = –19.9 kJ/mol and ΔS = –55.5 J/Kmol. The reaction will have ΔG = 0 at
________ K. Assume that ΔH and ΔS do not vary with temperature.
A) 359
B) 2789
C) 298
D) 2.79
E) 0.359
33) For a given reaction, ΔH = +35.5 kJ/mol and ΔS = +83.6 J/Kmol. The reaction is spontaneous
________. Assume that ΔH and ΔS do not vary with temperature.
A) at T < 425 K
B) at T > 425 K
C) at all temperatures
D) at T > 298 K
34) Under which of the following conditions would one mole of He have the highest entropy, S?
A) 17°C and 15 L
B) 127°C and 15 L
C) 17°C and 25 L
D) 127°C and 25 L
35) Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction.
SO3(g) + H2O(g) → H2SO4(l) ΔG°= -90.5 kJ
P(SO3) = 0.20 atm, P(H2O) = 0.88 atm
A) -90.5 kJ
B) -91.9 kJ
C) +91.9 kJ
D) -89.1 kJ
E) +89.1 kJ
36) Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction.
Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g) ΔG° = -28.0 kJ
P(CO) = 1.4 atm, P(CO2) = 2.1 atm
A) +31.0 kJ
B) -31.0 kJ
C) -28.0 kJ
D) +25.0 kJ
E) -25.0 kJ
37) In the Haber process, ammonia is synthesized from nitrogen and hydrogen:
N2(g) + 3H2 (g) → 2NH3 (g)
ΔG° at 298 K for this reaction is –33.3 kJ/mol. The value of ΔG at 298 K for a reaction mixture that
consists of 1.9 atm N2, 1.6 atm H2, and 0.65 atm NH3 is ________.
A) -1.8
B) -3.86 × 103
C) -7.25 × 103
D) -104.5
E) -40.5
38) 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 1.5 atm P2, 1.6 atm Cl2, and 0.65 atm PCl3 is ________.
A) -44.2
B) -3.88 ×
C) -7.28 × 103
D) -708.4
E) -649.5
Matching Questions
Match the following.
A) ΔG > ΔG°
B) ΔG < ΔG°
C) DG < 0
D) K = 0
E) standard state
F) equilibrium
G) ΔG > 0
1) Q = K
Diff: 1 Page Ref: 17.9
2) Q < K
Diff: 1 Page Ref: 17.9
3) Q > K
Diff: 1 Page Ref: 17.9
4) Q = 1
Diff: 1 Page Ref: 17.9
5) Q > 1
Diff: 1 Page Ref: 17.9
6) Q < 1
Diff: 1 Page Ref: 17.9
Short Answer Questions
1) Why is heating your home with gas more efficient than heating it with electricity?
2) Why can’t we say that a spontaneous reaction is a fast reaction?
3) Why can endothermic reactions be spontaneous?
4) Define entropy.
5) How many microstates are possible in a collection of four particles that are present, with two particles
each in two connected flasks? Sketch them below.
6) Define the second law of thermodynamics.
7) What is “free” energy? Give a fictitious example.
8) Give the standard states for a gas, liquid, solid, and solution.
9) Define the third law of thermodynamics.
10) Define allotrope.
11) How is a nonspontaneous process made spontaneous?
12) Why is the quantity of energy required to recharge a battery greater than the quantity of work done?