Graded Assignment 3- Fall 2012
Due Wed., Sep. 26, 2012
1. Which is the correct equilibrium constant expression for the following reaction?
Fe2O3(s) + 3H2(g) > 2Fe(s) + 3H2O(g)
a. Kc = [Fe2O3] [H2]3 / [Fe]2[H2O]3
b. Kc = [H2] / [H2O]
c. Kc = [H2O]3 / [H2]3
d. Kc = [Fe]2[H2O]3 / [Fe2O3] [H2]3
e. Kc = [Fe] [H2O] / [Fe2O3] [H2]
2. Consider the two gaseous equilibria:
SO2(g) + 1/2O2(g) > SO3(g)
2SO3(g) > 2SO2(g) + O2(g)
K1
K2
The values of the equilibrium constants K1 and K2 are related by
a. K2 = K12
b. K22 = K1
c. K2 = 1/K
d. K2 = 1/K1
e. none of these.
3. Carbon tetrachloride reacts at high temperatures with oxygen to produce two toxic gases, phosgene and
chlorine.
CCl4(g) + 1/2O2(g) > COCl2(g) + Cl2(g), Kc = 4.4 × 109 at 1,000 K
Calculate Kc for the reaction 2CCl4(g) + O2(g) > 2COCl2(g) + 2Cl2(g).
a. 4.4 × 109
b. 8.8 × 109
c. 1.9 × 1010
d. 1.9 × 1019
e. 2.3 × 10–10
4. Calculate Kp for the reaction 2NOCl(g)>2NO(g) + Cl2(g) at 400°C if Kc at 400°C for this reaction is
2.1 × 10–2.
a. 2.1 × 10–2
b. 1.7 × 10–3
c. 0.70
d. 1.2
e. 3.8 × 10–4
5. On analysis, an equilibrium mixture for the reaction 2H 2S(g)>2H2(g) + S2(g) was found to contain
1.0 mol H2S, 4.0 mol H2, and 0.80 mol S2 in a 4.0 L vessel. Calculate the equilibrium constant, Kc, for
this reaction.
a. 1.6
b. 3.2
c. 12.8
d. 0.64
e. 0.8
6. The reaction A(g) + 2B(g)>C(g) was allowed to come to equilibrium. The initial amounts of reactants
placed into a 5.00 L vessel were 1.0 mol A and 1.8 mol B. After the reaction reached equilibrium, 1.0 mol
of B was found. Calculate Kc for this reaction.
a. 0.060
b. 5.1
c. 17
d. 19
e. 25
7. At 35ºC, the equilibrium constant for the reaction 2NOCl(g)> 2NO(g) + Cl2(g) is Kc = 1.6 × 10–5. An
equilibrium mixture was found to have the following concentrations of Cl2 and NOCl: [Cl2] = 1.2 × 10–2
M; [NOCl] = 2.8 × 10–1 M. Calculate the concentration of NO(g) at equilibrium.
a. 1.0 × 10–4 M
b. 1.0 × 10–2 M
c. 2.8 × 10–1 M
d. 2.4 × 10–2 M
e. 1.6 × 10–3 M
8. At 400ºC, Kc = 64 for the equilibrium H2(g) + I2(g)>2HI(g). If 3.00 mol H2 and 3.00 mol I2 are
introduced into an empty 4.0 L vessel, find the equilibrium concentration of HI at 400ºC.
a. 0.15 M
b. 1.2 M
c. 2.4 M
d. 4.8 M
e. 5.8 M
9. For the reaction H2(g) + I2(g) > 2HI(g), Kc = 50.2 at 445ºC. If [H2] = [I2] = [HI] = 1.75 × 10–3 M at
445ºC, which one of these statements is true?
a. The system is at equilibrium, thus no concentration changes will occur.
b. The concentrations of HI and I2 will increase as the system approaches equilibrium.
c. The concentration of HI will increase as the system approaches equilibrium.
d. The concentrations of H2 and HI will fall as the system moves toward equilibrium.
e. The concentrations of H2 and I2 will increase as the system approaches equilibrium.
10. Consider this gas phase equilibrium system:
PCl5(g) > PCl3(g) + Cl2(g) ΔHºrxn = +87.8 kJ/mol.
Which of these statements is false?
a. Increasing the system volume shifts the equilibrium to the right.
b. Increasing the temperature shifts the equilibrium to the right.
c. A catalyst speeds up the approach to equilibrium and shifts the position of equilibrium to the
right.
d. Decreasing the total pressure of the system shifts the equilibrium to the right.
e. Increasing the temperature causes the equilibrium constant to increase.
11. When the reaction 2O3(g) > 3O2(g), for which Kp = 3.0 × 1026 at 773ºC, is at equilibrium, the
mixture will contain very little O2 as compared to O3.
a. True
b. False