Chemistry: A Molecular Approach, 2e (Tro)
Chapter 17 Free Energy and Thermodynamics
Multiple Choice Questions
1) Which of the following statements is TRUE?
A) There is a “heat tax” for every energy transaction.
B) A spontaneous reaction is always a fast reaction.
C) The entropy of a system always decreases for a spontaneous process.
D) Perpetual motion machines are a possibility in the near future.
E) None of the above are true.
2) The ________ Law of Thermodynamics states the energy is conserved in chemical processes.
A) Zero
B) First
C) Second
D) Third
E) Fourth
3) Identify the process that is spontaneous
A) rusting of iron
B) electrolysis
C) photosynthesis
D) bread rising
E) burning gasoline
4) ________ is a thermodynamic function that increases with the number of energetically equivalent
ways to arrange components of a system to achieve a particular state.
A) Heat of reaction
B) Free energy
C) Entropy
D) Enthalpy
E) Molar equivalence
5) The ________ Law of Thermodynamics states that for any spontaneous reaction, the entropy of the
universe increases.
A) Zero
B) First
C) Second
D) Third
E) Fourth
6) Which of the following processes have a ΔS > 0?
A) CH3OH(l) → CH3OH(s)
B) N2(g) + 3 H2(g) → 2 NH3(g)
C) CH4(g) + H2O(g) → CO(g) + 3 H2(g)
D) Na2CO3(s) + H2O(g) + CO2(g) → 2 NaHCO3(s)
E) All of the above processes have a DS > 0.
7) Which of the following statements is TRUE?
A) Entropy is not a state function.
B) Endothermic processes decrease the entropy of the surroundings, at constant T and P.
C) Endothermic processes are never spontaneous.
D) Exothermic processes are always spontaneous.
E) None of the above are true.
8) What is the sign of ΔSuniv for a biological system?
A) positive
B) negative
C) zero
D) It depends on the biological system.
9) Which of the following relationships is correct at constant T and P?
A) ΔG is proportional to –ΔSuniv
B) ΔG > 0 represents a spontaneous process
C) ΔG > 0 represents an increase in kinetic energy
D) ΔG < 0 represents a nonspontaneous process
E) All of the above are correct
3
10) Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is
TRUE?
A) This reaction will be spontaneous only at high temperatures.
B) This reaction will be spontaneous at all temperatures.
C) This reaction will be nonspontaneous at all temperatures.
D) This reaction will be nonspontaneous only at high temperatures.
E) It is not possible to determine without more information.
11) Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is
TRUE?
A) This reaction will be spontaneous only at low temperatures.
B) This reaction will be spontaneous at all temperatures.
C) This reaction will be nonspontaneous at all temperatures.
D) This reaction will be nonspontaneous only at low temperatures.
E) It is not possible to determine without more information.
12) Consider a reaction that has a negative ΔH and a positive ΔS. Which of the following statements is
TRUE?
A) This reaction will be spontaneous only at high temperatures.
B) This reaction will be spontaneous at all temperatures.
C) This reaction will be nonspontaneous at all temperatures.
D) This reaction will be nonspontaneous only at high temperatures.
E) It is not possible to determine without more information.
13) Consider a reaction that has a positive ΔH and a negative ΔS. Which of the following statements is
TRUE?
A) This reaction will be spontaneous only at high temperatures.
B) This reaction will be spontaneous at all temperatures.
C) This reaction will be nonspontaneous at all temperatures.
D) This reaction will be nonspontaneous only at high temperatures.
E) It is not possible to determine without more information.
14) Consider a reaction that has a negative ΔH and a negative ΔS. Which of the following statements is
TRUE?
A) This reaction will be spontaneous only at high temperatures.
B) This reaction will be spontaneous at all temperatures.
C) This reaction will be nonspontaneous at all temperatures.
D) This reaction will be nonspontaneous only at high temperatures.
E) It is not possible to determine without more information.
15) Consider a reaction that has a negative ΔH and a negative ΔS. Which of the following statements is
TRUE?
A) This reaction will be spontaneous only at low temperatures.
B) This reaction will be spontaneous at all temperatures.
C) This reaction will be nonspontaneous at all temperatures.
D) This reaction will be nonspontaneous only at low temperatures.
E) It is not possible to determine without more information.
16) For the following example, identify the following.
2 N2O(g) → 2 N2(g) + O2(g)
A) a negative ΔH and a negative ΔS
B) a positive ΔH and a negative ΔS
C) a negative ΔH and a positive ΔS
D) a positive ΔH and a positive ΔS
E) It is not possible to determine without more information.
17) For the following example, identify the following.
3O2(g) → 2O3(g)
A) a negative ΔH and a negative ΔS
B) a positive ΔH and a negative ΔS
C) a negative ΔH and a positive ΔS
D) a positive ΔH and a positive ΔS
E) It is not possible to determine without more information.
18) For the following example, identify the following.
H2O(l) → H2O(g)
A) a negative ΔH and a negative ΔS
B) a positive ΔH and a negative ΔS
C) a negative ΔH and a positive ΔS
D) a positive ΔH and a positive ΔS
E) It is not possible to determine without more information.
19) For the following example, identify the following.
H2O(l) → H2O(s)
A) a negative ΔH and a negative ΔS
B) a positive ΔH and a negative ΔS
C) a negative ΔH and a positive ΔS
D) a positive ΔH and a positive ΔS
E) It is not possible to determine without more information.
20) Above what temperature does the following reaction become nonspontaneous?
2 H2S(g) + 3 O2(g) → 2 SO2(g) + 2 H2O(g) ΔH = –1036 kJ; ΔS = -153.2 J/K
A) 6.762 × 103 K
B) 158.7 K
C) 298 K
D) This reaction is nonspontaneous at all temperatures.
E) This reaction is spontaneous at all temperatures.
21) Above what temperature does the following reaction become nonspontaneous?
FeO(s) + CO(g) → CO2(g) + Fe(s) ΔH = –11.0 kJ; ΔS = -17.4 J/K
A) 632 K
B) 298 K
C) 191 K
D) This reaction is nonspontaneous at all temperatures.
E) This reaction is spontaneous at all temperatures.
22) Below what temperature does the following reaction become nonspontaneous?
2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) ΔH = +136.5 kJ; ΔS = +287.5 J/K
A) 39.2 K
B) 151 K
C) 475 K
D) This reaction is nonspontaneous at all temperatures.
E) This reaction is spontaneous at all temperatures.
23) The ________ Law of Thermodynamics states the entropy of a perfect crystal at absolute zero is
zero.
A) Zero
B) First
C) Second
D) Third
E) Fourth
24) For a given compound, list the decreasing order of entropy for a liquid, solid, and gas
A) solid > gas > liquid
B) liquid > solid > gas
C) gas > liquid > solid
D) gas > solid > liquid
E) solid > liquid > gas
25) Which of the following statements is TRUE?
A) Entropy is an extensive property.
B) Entropy is not temperature dependent.
C) Exothermic processes decrease the entropy of the surroundings.
D) ΔSuniverse is always greater than zero for a nonspontaneous process.
E) None of the above are true.
26) Identify the statement that is FALSE.
A) The entropy of a gas is greater than the entropy of a liquid.
B) Entropy generally increases with increasing molecular complexity.
C) Free atoms have greater entropy than molecules.
D) Entropy increases with dissolution.
E) For noble gasses, entropy increases with size.
27) Place the following in order of increasing entropy at 298 K.
Ne Xe He Ar Kr
A) He < Kr < Ne < Ar < Xe
B) Xe < Kr < Ar < Ne < He
C) Ar < He < Ar < Ne < Kr
D) Ar < Ne < Xe < Kr < He
E) He < Ne < Ar < Kr < Xe
28) Place the following in order of increasing molar entropy at 298 K.
NO CO SO
A) NO < CO < SO
B) SO < CO < NO
C) SO < NO < CO
D) CO < SO < NO
E) CO < NO < SO
29) Place the following in order of decreasing molar entropy at 298 K.
H2 Cl2 F2
A) H2 > Cl2 > F2
B) Cl2 > H2 > F2
C) F2 > Cl2 > H2
D) H2 > F2 > Cl2
E) Cl2 > F2 > H2
30) Place the following in order of increasing standard molar entropy.
H2O(l) H2O(g) H2O(s)
A) H2O(g) < H2O(l) < H2O(s)
B) H2O(s) < H2O(l) < H2O(g)
C) H2O(g) < H2O(s) < H2O(l)
D) H2O(l) < H2O(s) < H2O(g)
E) H2O(s) < H2O(g) < H2O(l)
31) Place the following in order of decreasing standard molar entropy.
N2O4(g) NO(g) NO2(g)
A) N2O4 > NO2 > NO
B) NO > NO2 > N2O4
C) N2O4 > NO > NO2
D) NO > N2O4 > NO2
E) NO2 > NO > N2O4
8
32) Which one of the following has the highest standard molar entropy, S°, at 25°C?
A) H2(g)
B) F2(g)
C) O2(g)
D) N2(g)
E) Cl2(g)
33) Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction.
C2H2(g) + H2(g) → C2H4(g)
S°(J/mol∙K) 200.9 130.7 219.3
A) +112.3 J/K
B) +550.9 J/K
C) -112.3 J/K
D) +337.1 J/K
E) -550.9 J/K
34) Calculate ΔS°rxn for the following reaction. The S∘ for each species is shown below the reaction.
C2H2(g) + 2 H2(g) → C2H6(g)
S°(J/mol∙K) 200.9 130.7 229.2
A) +303.3 J/K
B) +560.8 J/K
C) -102.4 J/K
D) -233.1 J/K
E) 229.2 J/K
35) Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction.
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)
S°(J/mol∙K) 192.8 205.2 210.8 188.8
A) +287.4 J/K
B) -401.2 J/K
C) +160.0 J/K
D) -336.6 J/K
E) +178.8 J/K
36) Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction.
N2H4(l) + H2(g) → 2 NH3(g)
S° (J/mol∙K) 121.2 130.7 192.8
A) +133.7 J/K
B) -59.1 J/K
C) +118.2 J/K
D) -202.3 J/K
E) +178.9 J/K
37) Calculate DS°rxn for the following reaction. The S° for each species is shown below the reaction.
P4(g) + 10 Cl2(g) → 4 PCl5(g)
S°(J/mol∙K) 280.0 223.1 364.6
A) -138.5 J/K
B) -1052.6 J/K
C) +171.3 J/K
D) -583.6 J/K
E) +2334.6 J/K
38) What can change the direction of a reversible reaction?
A) change in temperature
B) change in pressure
C) change in volume
D) none of the above
E) all of the above
39) Give the name of the reaction that achieves the theoretical limits with respect to free energy in
thermodynamics.
A) reversible reaction
B) forward reaction
C) reverse reaction
D) equilibrium reaction
E) irreversible reaction
40) Give the name of the reaction that does not achieve the theoretical limits with respect to free energy
in thermodynamics.
A) reversible reaction
B) forward reaction
C) reverse reaction
D) equilibrium reaction
E) irreversible reaction
41) Given the following equation,
N2O(g) + NO2(g) → 3 NO(g) ΔG°rxn = -23.0 kJ
Calculate ΔG°rxn for the following reaction.
3 NO(g) → N2O(g) + NO2(g)
A) -23.0 kJ
B) 69.0 kJ
C) -69.0 kJ
D) -7.67 kJ
E) 23.0 kJ
42) Determine ΔG°rxn using the following information.
H2(g) + CO(g) → CH2O(g) ΔH°= +1.9 kJ; ΔS°= -109.6 J/K
A) +57.7 kJ
B) -30.8 kJ
C) +34.6 kJ
D) -41.5 kJ
E) +17.3 kJ
43) Calculate the ΔG°rxn using the following information.
4 HNO3(g) + 5 N2H4(l) → 7 N2(g) + 12 H2O(l) ΔG°rxn = ?
ΔG°f (kJ/mol) -73.5 149.3 -237.1
A) -3.298 x 103 kJ
B) -312.9 kJ
C) +2.845 x 103 kJ
D) +110.7 kJ
E) -954.7 kJ
44) Calculate the ΔG°rxn using the following information.
2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) ΔG°rxn = ?
ΔG°f (kJ/mol) -110.9 87.6 51.3 -237.1
A) -162.5 kJ
B) +51.0 kJ
C) -54.5 kJ
D) +171.1 kJ
E) -87.6 kJ
45) Use Hess’s law to calculate ΔG°rxn using the following information.
CO(g) → C(s) + 1/2 O2(g) ΔG°rxn = ?
CO2(g) → C(s) + O2(g) ΔG°rxn = +394.4 kJ
CO(g) + 1/2 O2(g) → CO2(g) ΔG°rxn = -257.2 kJ
A) -60.0 kJ
B) +651.6 kJ
C) -265.8 kJ
D) +137.2 kJ
E) +523.0 kJ
46) Use Hess’s law to calculate ΔG°rxn using the following information.
ClO(g) + O3(g) → Cl(g) + 2 O2(g) ΔG°rxn = ?
2 O3(g)→ 3 O2(g) ΔG°rxn = +489.6 kJ
Cl(g) + O3(g) → ClO(g) + O2(g) ΔG°rxn = -34.5 kJ
A) -472.4 kJ
B) -210.3 kJ
C) +455.1 kJ
D) +262.1 kJ
E) +524.1 kJ
47) Calculate the ΔG°rxn using the following information.
2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) ΔG°rxn = ?
ΔH°f (kJ/mol) -207.0 91.3 33.2 -285.8
S°(J/mol∙K 146.0 210.8 240.1 70.0
A) -151 kJ
B) -85.5 kJ
C) +50.8 kJ
D) +222 kJ
E) -186 kJ
48) Calculate the ΔG°rxn using the following information.
4 HNO3(g) + 5 N2H4(l) → 7 N2(g) + 12 H2O(l) ΔG°rxn = ?
ΔH°f (kJ/mol) –133.9 50.6 -285.8
S°(J/mol∙K) 266.9 121.2 191.6 70.0
A) +4.90 × 103 kJ
B) +3.90 × 103 kJ
C) -2.04 × 103 kJ
D) -3.15 × 103 kJ
E) -3.30 x 103 kJ
49) Calculate the ΔG°rxn using the following information.
2 H2S(g) + 3 O2(g) → 2 SO2(g) + 2 H2O(g) ΔG°rxn = ?
ΔH°f (kJ/mol) -20.6 -296.8 -241.8
S°(J/mol∙K) 205.8 205.2 248.2 188.8
A) -990.3 kJ
B) +108.2 kJ
C) -466.1 kJ
D) +676.2 kJ
E) -147.1 kJ
50) Use Hess’s law to calculate ΔG°rxn using the following information.
NO(g) + O(g) → NO2(g) ΔG°rxn = ?
2 O3(g) → 3 O2(g) ΔG°rxn = +489.6 kJ
O2(g) → 2 O(g) ΔG°rxn = +463.4 kJ
NO(g) + O3(g) → NO2(g) + O2(g) ΔG°rxn = – 199.5 kJ
A) +753.5 kJ
B) +277.0 kJ
C) -676.0 kJ
D) -1152.5 kJ
E) -225.7 kJ
51) Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction.
3 O2(g) → 2 O3(g) ΔG° = +326 kJ
P(O2) = 0.41 atm, P(O3) = 5.2 atm
A) +341 kJ
B) +17.8 kJ
C) +332 kJ
D) -47.4 kJ
E) -109 kJ
52) Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction.
2 Hg(g) + O2(g) → 2 HgO(s) ΔG° = -180.8 kJ
P(Hg) = 0.025 atm, P(O2) = 0.037 atm
A) +207 kJ
B) -154.4 kJ
C) -26.5 kJ
D) -164 kJ
E) +60.7 kJ
53) Calculate ΔGrxn at 298 K under the conditions shown below for the following reaction.
CaCO3(s) → CaO(s) + CO2(g) ΔG° =+131.1 kJ
P(CO2) = 0.033 atm
A) -49.3 kJ
B) -8.32 kJ
C) +122.6 kJ
D) +39.7 kJ
E) +43.3 kJ
54) Which of the following is NOT true for ΔGrxn?
A) If ΔG°rxn > 0, the reaction is spontaneous in the forward direction.
B) If Q = 1, then DGrxn = ΔG°rxn.
C) If ΔG°rxn = 0, the reaction is spontaneous in the reverse direction.
D) If ΔG°rxn > 0, the reaction is spontaneous in the reverse direction.
E) Under equilibrium conditions, ΔGrxn = 0.
55) Choose the statement below that is TRUE.
A) K > 1, ΔG°rxn is positive.
B) K < 1, ΔG°rxn is negative.
C) ΔG°rxn = 0 at equilibrium.
D) ΔGrxn = 0 at equilibrium.
E) None of the above statements are true.
56) What is true if ln K is negative?
A) ΔGorxn is positive and the reaction is spontaneous in the forward direction.
B) ΔGorxn is negative and the reaction is spontaneous in the forward direction.
C) ΔGorxn is negative and the reaction is spontaneous in the reverse direction.
D) ΔGorxn is positive and the reaction is spontaneous in the reverse direction.
E) ΔGorxn is zero and the reaction is at equilibrium.
57) What is true if ln K is positive?
A) ΔGorxn is positive and the reaction is spontaneous in the forward direction.
B) ΔGorxn is negative and the reaction is spontaneous in the forward direction.
C) ΔGorxn is negative and the reaction is spontaneous in the reverse direction.
D) ΔGorxn is positive and the reaction is spontaneous in the reverse direction.
E) ΔGorxn is zero and the reaction is at equilibrium.
58) What is true if ln K is zero?
A) ΔGorxn is positive and the reaction is spontaneous in the forward direction.
B) ΔGorxn is negative and the reaction is spontaneous in the forward direction.
C) ΔGorxn is negative and the reaction is spontaneous in the reverse direction.
D) ΔGorxn is positive and the reaction is spontaneous in the reverse direction.
E) ΔGorxn is zero and the reaction is at equilibrium.
59) Which of the following reactions will have the largest equilibrium constant (K) at 298 K?
A) CaCO3(s) → CaO(s) + CO2(g) ΔG° =+131.1 kJ
B) 2 Hg(g) + O2(g) → 2 HgO(s) ΔG° = -180.8 kJ
C) 3 O2(g) → 2 O3(g) ΔG° = +326 kJ
D) Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g) ΔG° = -28.0 kJ
E) It is not possible to determine without more information.
60) Use the free energies of formation given below to calculate the equilibrium constant (K) for the
following reaction at 298 K.
2 HNO3(aq) + NO(g) → 3 NO2(g) + H2O(l) K = ?
ΔG°f (kJ/mol) -110.9 87.6 51.3 -237.1
A) 8.71 × 108
B) 0.980
C) 1.15 × 10-9
D) 1.02
E) 5.11 × 10-4