Chapter 15 - Chemical Equilibrium, Review
1. Write the equilibrium equations (Kc) for each of the following reactions: a) 2SO2(g) + O2(g) 2SO3(g) b) 2SO3(g) 2SO2(g) + O2(g) 2. The following equilibrium concentrations were measured at 800K. [SO2] = 3.0 x 10-3M, -3 -2 [O2] = 3.5 x 10 M and [SO3] = 5.0 x 10 M. Calculate the equilibrium constant at 800K for each of the reactions in problem 1. 3. Write the equilibrium equations (Kc) for each of the following reactions: a) 2Fe(s) + 3H2O(g) Fe2O3(s) + 3H2(g) b) 2H2O(g) 2H2(g) + O2(g) 4. The equilibrium constant Kc for the reaction 2NO(g) + O2(g) 2NO2(g) is 6.9 x 5 10 is 500K. A 5.0L reaction vessel at this temperature was filled with 0.060 mol of No, 1.0 mol of O2, and 0.80 mol of NO2. a) Is this reaction mixture at equilibrium? If not, in which direction does the reaction proceed? 5. The H2 and CO ratio in mixtures of carbon monoxide and hydrogen synthesis gas is increased by the gas shift reaction, CO(g) + H2O CO2(g) + H2(g), which has an equilibrium constant Kc = 4.24 at 800K. Calculate the equilibrium concentrations of CO2, H2, CO, and H2O at 800K if only CO and H2O are present initially at concentrations of 0.150M. 6. Calculate the equilibrium concentrations of N2O4 and NO2 at 25°C in a vessel that contains an initial N2O4 concentration of 0.0500M. The equilibrium -3 constant for the reaction N2O4(g) 2NO2(g) is 4.64 x 10 at 25°C. 7. Consider the equilibrium for the gas shift reaction: CO(g) + H2O(g) CO2(g) + H2(g) Use Le Chatelier’s Principle to predict how the concentration of H2 will change when the equilibrium is disturbed by: a) adding CO b) adding CO2 c) removing H2O d) removing CO2 e) account for the change in terms of the reaction quotient Qc. 8. Does the number of moles of reaction products increase, decrease, or remain the same when each of the following equilibria is subjected to an increase in pressure by decreasing the volume? a) CO(g) + H2O(g) CO2(g) + H2(g) b) 2CO(g) C(s) + CO2(g) c) N2O4(g) 2NO2(g) 9. Ethyl acetate, a solvent used as fingernail-polish remover, is made by the reaction of acetic acid with ethanol: CH3COOH(l) + C2H5OH(l) CH3COOC2H5(l) + H2O(l) ΔH° = -2.9kJ Does the amount of ethyl acetate in an equilibrium mixture increase or decrease when the temperature is increased? How does Kc change when the temperature is decreased? Justify your answers using Le Chatelier’s Principle.
1 10. A platinum catalyst is used in automobile catalytic converters to hasten the oxidation of carbon monoxide: 2CO(g) + O2(g) 2CO2(g) ΔH° = -566kJ Suppose that you have a reaction vessel containing an equilibrium mixture of CO(g), O2(g), and CO2(g). Will the amount of CO increase, decrease, or remain the same when: a) a platinum catalyst is added b) the temperature is increased c) the pressure is increased by decreasing the volume 11. List three factors that can alter the composition of an equilibrium mixture. Which of these factors affects the value of the equilibrium constant? 12. Explain why a catalyst does not affect the composition of an equilibrium mixture. 13. Consider the reaction C(s) + CO2(g) 2CO(g). When 1.50 mol of CO2 and an excess of solid carbon are heated in a 20.0L container at 1100K, the equilibrium concentration of CO is 7.00 x 10-2M. Calculate: a) the equilibrium concentration of CO2 b) the value of the equilibrium constant Kc at 1100K 14. The equilibrium concentrations in a gas mixture at a particular temperature are 0.13M H2, 0.70M I2, and 2.1M HI. What equilibrium concentrations are obtained at the same temperature when 0.20 mol of HI is injected into an empty 500mL container? 15. A 5.00L reaction vessel is filled with 1.00 mol of H2, 1.00 mol of I2, and 2.50 mol of HI. Calculate the equilibrium concentrations of H2, I2, and HI at 500K. The equilibrium constant Kc at 500K for the reaction H2(g) + I2(g) 2HI(g) is 129. 16. At 1000K, the value of Kc for the reaction C(s) + H2O(g) CO2(g) + H2(g) is 3.0 -2 x 10 . Calculate the equilibrium concentrations of H2O, CO2, and H2 in a reaction mixture obtained by heating 6.00 mol of steam and an excess of solid carbon in a 5.00L container. What is the molar composition of the equilibrium mixture?
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