314 7 Chemical EquilibriumPROBLEMS
Section 7.2: Reactions Involving Gases and Pure Solids or
Liquids
7.4Find the value of the equilibrium constant for the reaction
of Problem 7.1 from the∆G◦value and compare it with
the value found graphically in Problem 7.1.
7.5a.Find the value of the equilibrium constant at 298.15 K
for the reaction2SO 2 (g)+O 2 (g)2SO 3 (g)b.0.2000 mol of SO 2 and 0.1000 mol of O 2 are mixed and
maintained at a constant total pressure of 1.000 bar and
a constant temperature of 298.15 K. Find the
equilibrium partial pressure of each gas.
7.6A mixture of 1.000 mol of N 2 and 3.000 mol of H 2 was
placed in contact with a catalyst and allowed to come to
equilibrium at 450◦C. It was found that the mole fraction of
NH 3 was equal to 0.0402 at a total pressure of 10.00 atm.
a.Find the value of the equilibrium constant at this
temperature for the reactionN 2 +3H 2 2NH 3b.Find the value of∆G◦for this reaction at 450◦C.
c.Calculate the value of∆fG◦(NH 3 ) at this temperature.
7.7For the reactionH 2 (g)+D 2 (g)2HD(g)where D is^2 H(deuterium),
a.Find∆H◦and∆S◦at 298.5 K.
b.Find∆G◦andKat 298.15 K.
c.Find the equilibrium partial pressure of each gas at a
total pressure of 1.000 bar and a temperature of
298.15 K, starting with an equimolar mixture
of H 2 and D 2.
d.Construct a graph ofG−G(initial) as a function of the
progress variableξ, starting with 0.500 mol of H 2 and
0.500 mol of D 2 and maintaining a temperature of
298.15 K and a total pressure of 1.000 bar.
Data for HD(g) at 298.15 K:
∆fH◦ 0 .33 kJ mol−^1 ,∆fG◦− 1 .46 kJ mol−^1 ,
Sm◦ 143 .69JK−^1 mol−^1
Data for D 2 (g) at 298.15 K:
∆fH◦0kJmol−^1 ,∆fG◦0kJmol−^1 ,
Sm◦ 144 .85 J K−^1 mol−^17.8Find the standard-state Gibbs energy change at 298.15 K for
each of the reactions:
a.2NO(g)+O 2 (g)N 2 O 4 (g)
b. 4NO 2 (g)+O 2 (g)2N 2 O 5 (g)
7.9Find the standard-state Gibbs energy change at 298.15 K for
each of the reactions:
a.2SO 2 (g)+O 2 (g)2SO 3 (g)
b.S(s,rhombic)+O 2 (g)O 2 (g)
c.2NO(g)+O 2 (g)2NO 2 (g)
7.10 Using formation values and third-law entropies, find∆H◦,
∆S◦, and∆G◦for each of the following reactions.
Calculate∆H◦−T∆S◦and compare it with∆G◦to check
the consistency of the data.
a.2 HgO(s)2Hg(l)+O 2 (g)
b.CaCO 3 (calcite,s)+2HCl(g)CaCl 2 (s)+H 2 O(l)+
CO 2 (g)
7.11 Using formation values and third-law entropies, find∆H◦,
∆S◦, and∆G◦for each of the following reactions.
Calculate∆H◦−T∆S◦and compare it with∆G◦to check
the consistency of the data.
a.2 Mg(s)+O 2 (g)2MgO(s)
b.CaCO 3 (calcite,s)CaO(s)+CO 2 (g)
7.12 Find the equilibrium constant at 298.15 K for each of the
reactions of Problem 7.10.
7.13 Find the equilibrium constant at 298.15 K for each of the
reactions of Problem 7.11.
7.14 a.Find the value of the equilibrium constant at 298.15 K
for the reactionPCl 5 (g) PCl 3 (g)+Cl 2 (g)b.Find the total pressure if 0.00100 mol of PCl 5 (g) is
placed in a vessel with a volume of 20.000 L at 298.15 K
and allowed to equilibrate. Assume ideal gas behavior.
7.15 The equilibrium constant for the reactionN 2 O 4 (g)2NO 2is equal to 0.148 at 298.15 K. If a system containing these
gases is maintained at a constant total pressure of 1.000 bar
and a temperature of 298.15 K, find the partial pressure of
each gas at equilibrium.