Chapter 17 – Entropy, Free Energy, and Equilibrium
100. Consider the reaction CO(g) + 2H2(g) CH3OH(l) at 25C.
Gf (CO) = –137.3 kJ/mol
Gf (CH3OH) = –166.3 kJ/mol
Hf (CO) = –110.5 kJ/mol
Hf (CH3OH) = –238.7 kJ/mol
S(CO) = 197.9 J/K·mol
S(CH3OH) = 126.8 J/K·mol
Calculate the value of the equilibrium constant (Kp) for this reaction at 25C.
Chapter 17 – Entropy, Free Energy, and Equilibrium
101. Consider the reaction CO(g) + 2H2(g) CH3OH(l) at 25C.
Gf (CO) = –137.3 kJ/mol
Gf (CH3OH) = –166.3 kJ/mol
Hf (CO) = –110.5 kJ/mol
Hf (CH3OH) = –238.7 kJ/mol
S(CO) = 197.9 J/K·mol
S(CH3OH) = 126.8 J/K·mol
Calculate S(H2(g)).
102. For the reaction H2O2(g) → H2O(g) + 1/2O2(g), H = –106 kJ/mol and S = 58
J/K·mol at 25C. Calculate G for this reaction at this temperature.
Chapter 17 – Entropy, Free Energy, and Equilibrium
103. Select True or False: For the reaction H2O2(g) → H2O(g) + 1/2O2(g), H = –106 kJ/mol
and S = 58 J/K·mol at 25C. H2O2(g) is stable with respect to dissociation into water vapor
and oxygen gas at 25C.
104. Select True or False: At a given temperature, O2(g) at 5 atm has a higher entropy per
mole than O2(g) at 0.5 atm.
105. Select True or False: At a given temperature, Br2(l) has a higher entropy per mole than
Br2(g).
Chapter 17 – Entropy, Free Energy, and Equilibrium
106. Select True or False: At a given temperature, 1 mole of N2(g) in a 22.4 L container has a
higher entropy per mole than 1 mole of N2(g) in a 2.24 L container.
107. Select True or False: At a given temperature, CO2(g) has a higher entropy per mole than
CO2(aq).
108. Hvap for ethanol is 38.7 kJ/mol at its boiling point (78C). What is Ssurr when 1.00
mole of ethanol is boiled?
Chapter 17 – Entropy, Free Energy, and Equilibrium
109.
Using the thermodynamic data provided below, determine the temperature in C at which the decomposition of solid calcium
carbonate to form solid calcium oxide and oxygen becomes spontaneous.
Chapter 17 – Entropy, Free Energy, and Equilibrium
110.
Sulfur can be separated from lead in the mineral galena, PbS(s), by “roasting” the ore in the presence of oxygen as shown in
the following reaction:
2PbS(s) + 3O2(g) → 2PbO(s) + 2SO2(g)
Determine G for the above reaction at 850C.
Chapter 17 – Entropy, Free Energy, and Equilibrium
111.
Given the following data, calculate the boiling point of HCOOH (formic acid).
Chapter 17 – Entropy, Free Energy, and Equilibrium
112.
Given the following data, estimate the boiling point of carbon disulfide, CS2, assuming that S and H are temperature-
independent.
Chapter 17 – Entropy, Free Energy, and Equilibrium
113.
Given the following data, estimate the boiling point of bromine, Br2, assuming that S and H are temperature-
independent.
Topic: Thermodynamics (Entropy and Free Energy)
114. At 700 K, the equilibrium constant for the reaction CO(g) + H2O(g) CO2(g) +
H2(g) is 5.10. What is G for this reaction at this temperature?
Chapter 17 – Entropy, Free Energy, and Equilibrium
115.
Using the thermodynamic data provided below, calculate Ka for HCN(aq) at 25.
Chapter 17 – Entropy, Free Energy, and Equilibrium
116.
Using the thermodynamic data provided below, calculate Ka1 for H2CO3(aq) at 25.
Chapter 17 – Entropy, Free Energy, and Equilibrium
117.
Using the thermodynamic data provided below, calculate Ka2 for H2CO3(aq) at 25.
Chapter 17 – Entropy, Free Energy, and Equilibrium
118.
Using the thermodynamic data provided below, calculate Ksp for ZnS(s) at 25.
Chapter 17 – Entropy, Free Energy, and Equilibrium
119.
Using the thermodynamic data provided below, calculate Ksp for Mg(OH)2(s) at 25.
Chapter 17 – Entropy, Free Energy, and Equilibrium
121. Select True or False: The entropy of any pure substance at 0 K is 0 J/mol.
122. Select True or False: The entropy of a perfectly ordered crystalline substance at 0 K is 0
J/mol.
123. Select True or False: Melting an ionic solid always results in an increase in entropy.
124. Select True or False: Dissolving an ionic solid in water always results in an increase in
entropy.
Chapter 17 – Entropy, Free Energy, and Equilibrium
125. Select True or False: For a given substance the entropy always increases in the following
order:
126. Select True or False: The entropy change S for the reaction NH4Cl(s) → NH3(g) +
HCl(g) will be negative.
127. Select True or False: The following reaction is spontaneous under standard state
conditions at 25C:
Chapter 17 – Entropy, Free Energy, and Equilibrium
128. Select True or False: For any pure substance, if Hf = 0 and Gf = 0, then S = 0.