Chemistry 360
Spring 2017
Dr. Jean M. Standard
April 3, 2017
Problem Set 9
Good problems in Engel & Reid (3rd ed.): 6.2, 6.4, 6.6, 6.8, 6.13, 6.24, 6.30, 6.38
1.
The following chemical reaction converts sulfur dioxide to sulfur trioxide.
SO 2 ( g) +
1O
2 2
( g)
SO 3 ( ℓ) .
(a.) Write the expression for K eq for this reaction.
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(b.) Calculate the value of the standard molar Gibbs free energy of reaction, ΔGR! , for this reaction at 298 K
using standard €
molar Gibbs free energies of formation found in the appendix of your textbook.
(c.) Calculate the value of K eq for this reaction.
(d.) If 1.0 bar of SO2 and 1.0 bar of O2 are enclosed in a system in the presence of some SO3 liquid, in which
direction will€the system move in order to reach equilibrium?
2.
Calculate the equilibrium constant and standard molar Gibbs free energy of reaction at 20°C for the reaction
CuSO 4 ⋅ 4NH 3 (s)
CuSO 4 ⋅ 2NH 3 (s) + 2 NH 3 ( g) .
The equilibrium pressure of ammonia gas at 20°C is 8.26 kPa.
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3.
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At 500 K, the equilibrium constant is 0.0408 for the reaction
PCl3 ( g) + Cl2 ( g)
PCl5 ( g) .
The standard molar enthalpy of reaction is ΔH R! = −69.8 kJ/mol . Determine the equilibrium constant at 700 K,
assuming the standard molar
enthalpy of reaction is independent
of temperature over this range.
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4.
The dissociation of mercuric oxide can be described by the reaction
2 HgO (s)
2 Hg (g) + O2 (g) .
4
5
The total pressure at equilibrium is 5.16×10 Pa at 420°C and 1.08×10 Pa at 450°C. By expressing the
equilibrium constant in terms of partial pressures, determine the equilibrium constant at each temperature. Also
determine the standard enthalpy of reaction, assuming it is independent of temperature over the range.
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5.
Consider the following reaction,
3 O 2 ( g)
2 O 3 ( g) .
(a.) Without performing a calculation, predict in which direction the equilibrium will shift as the pressure is
increased.
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(b.) Using data for standard molar enthalpies found in the appendix of your textbook, predict in which direction
the equilibrium will shift as the temperature is increased.
(c.) Using data for standard molar Gibbs energies found in the appendix of your textbook, calculate the
equilibrium constant for the reaction at 298 K. Then, calculate the equilibrium constant for the reaction at
600 K, assuming that ΔH R! is independent of temperature. Repeat the calculation at 700 K. Compare your
results with your answer from part (b).
6.
At 2000°C and a total pressure of 1 atm, water is 2% dissociated into oxygen and hydrogen gas according to the
reaction
H 2O ( g)
H 2 ( g) +
1
2
O 2 ( g) .
(a.) Calculate the equilibrium constant for the reaction.
(b.) Determine whether
increases or decreases if the pressure is reduced.
€
€ the extent of reaction
(c.) If the total pressure is fixed at 1 atm, determine whether the extent of reaction increases or decreases if
argon gas is added.
(d.) Determine whether the extent of reaction increases or decreases if oxygen gas is added and the total
pressure remains constant at 1 atm.