Name Chem 6 Section #

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1 Equilibrium Constant and its Meaning 1. Write the expressions for K eq for the following reactions. a) CH 4 (g) + 2 H 2 S(g) CS 2 (g) + 4 H 2 (g) b) 2 N 2 O 5 (g) 4 NO 2 (g) + O 2 (g) c) 3 O 2 (g) 2 O 3 (g) 2. The equilibrium constant for the reaction below is K c = 2.4 x 10 3 at 700 o C. 2 SO 3 (g) 2 SO 2 (g) + O 2 (g) a) Calculate K p for this reaction at 700 o C. A) 2.4 x 10 3 B) C) D) 15.3 b) Calculate K c for the reaction 4 SO 2 (g) + 2 O 2 (g) 4 SO 3 (g) at 700 o C. A) 2.4 x 10 3 B) 4.8 x 10 3 C) 4.2 x 10 2 D) 1.7 x 10 5 c) At this temperature, does the equilibrium favor SO 3, or does it favor SO 2 and O 2? Class 14 Page 1 Group Work

2 3. Which one of the following has the greatest tendency to proceed as written? (a) 4NH3(g) + 3O2(g) 2N2(g) + 6H2O(g) Kp = (b) N2(g) + O2(g) 2NO(g) Kp = (c) 2HF(g) F2(g) + H2(g) Kp = (d) 2NOCl(g) 2NO(g) + Cl2(g) Kp = Arrange the reactions in order of their increasing tendency to proceed toward completion. 4A. For which of the reactions below is K c = K p? (There can be more than one correct answer.) a) N 2 (g) + 3 H 2 (g) 2 NH 3 (g) b) H 2 (g) + Br 2 (g) 2 HBr(g) c) CH 4 (g) + 2 H 2 S(g) CS 2 (g) + 4 H 2 (g) d) 2 N 2 O 5 (g) 4 NO 2 (g) + O 2 (g) 4B For which reactions is K c > K P? (There can be more than one correct answer.) 4. The equilibrium constant at 100 C for the following reaction is COCl 2 (g) CO(g) + Cl 2 (g) The equilibrium mixture should be a) mostly COCl 2 (g) b) mostly CO (g) c) mostly Cl 2 (g) d) an equal mixture of CO(g) and Cl 2 (g) with almost no COCl 2 (g) 5. There is not enough information to determine anything about the equilibrium mixture. Class 14 Page 2 Group Work

3 Heterogeneous Equilibria 1. Which of the following reactions involve heterogeneous equilibria? (There is more than one correct answer.) (a) CO(g) + 2H2(g) CH3OH(g) (b) PCl3(g) + Cl2(g) PCl5(g) (c) 2H2S(g) + 3O2(g) 2H2O(g) +2SO2(g) (d) NiO(s) + CO(g) Ni(s) +CO2(g) (e) BaSO4(s) Ba 2+ (aq) + SO4 2 (aq) Write equilibrium expressions for Keq for each of the reactions. 2. The value of K c for this reaction is 1.10 at 25 C. What is the value of K p for this reaction at the same temperature? 4CuO(s) + CH 4 (g) CO 2 (g) + 4Cu(s) + 2H 2 O(g) a) 658 b) 37.2 c) 26.9 d) 4.63 e) Class 14 Page 3 Group Work

4 Equilibrium: Reaction Quotient 1. The equilibrium constant for the following reaction at 150 C is IBr(g) Br2(g)+ I2(g) If there are 0.02 moles of I2, 0.05 moles of Br2 and 0.30 moles of IBr then a) the system is at equilibrium. b) the system is not at equilibrium and the products will react to produce more IBr(g) in order to get to equilibrium. (The reaction will proceed to the left.) c) the system is not at equilibrium and the reactant (IBr) will react to produce more Br2(g) and I2(g) in order to get to equilibrium. (The reaction will proceed to the right.) d) the system can never get to equilibrium. Show all calculations and explain your reasoning. HINT Evaluate Q (the reaction quotient) for this set of concentrations. What does Q tell you about the extent and direction of a reaction? 2. Consider the following reaction at a constant temperature for which K eq = 2.7. CO(g) + H 2 O(g) CO 2 (g) + H 2 (g) If mole of CO, mole of H 2 O, mole of CO 2 and mole of H 2 are introduced into a 2 L vessel, which of the following statements will be true? a) The system is at equilibrium and no change will occur. b) The system is not at equilibrium and will proceed to the right to achieve equilibrium. c) The system is not at equilibrium and will proceed to the left to achieve equilibrium. d) The system is not at equilibrium and it cannot achieve equilibrium. e) The system is at equilibrium, but the addition of a catalyst will cause the reaction to proceed to the right. Class 14 Page 4 Group Work

5 Equilibrium Problems 1. A mixture of mol of CO 2, mol of H 2, and mol of H 2 O is placed in a 1.0 L vessel. The following equilibrium is established: CO 2 (g) + H 2 (g) CO(g) + H 2 O(g) At equilibrium, [CO 2 ] = M. Calculate the equilibrium concentrations of H 2, CO, and H 2 O. [H 2 ] [CO] [H 2 O] a) b) c) d) At temperatures near 800 o C, steam passed over hot coke (a form of carbon obtained from coal), reacts to form CO and H 2 : C(s) + H 2 O(g) CO(g) + H 2 (g) The mixture of gases that results is an important industrial fuel called water gas. When equilibrium is achieved at 800 o C, [H 2 ] = 4.0 x 10 2 M, [CO] = 4.0 x 10 2, and [H 2 O] = 1.0 x 10 2 M. Calculate K c at this temperature a) 0.16 b) c) 4.0 d) 6.25 e) There is not enough information to answer this question. Class 14 Page 5 Group Work

6 3. A mixture of g of H 2 and g of Br 2 is heated in a 2.00 L vessel at 700 K. These substances react as follows: H 2 (g) + Br 2 (g) 2 HBr(g) At equilibrium the vessel is found to contain g of H 2. a) Calculate the equilibrium concentrations of H 2, Br 2, and HBr. [H 2 ] [Br 2 ] [HBr] a) b) c) d) b) Calculate K c. a) b) 14.3 c) 15.2 d) e) Class 14 Page 6 Group Work

7 Le Chatelier s Principle 1. Considering the following equilibrium situation: 2N2O(g) + O2(g) 4NO(g) How will the amount of NO present at equilibrium be affected when other disturbances occur? (Write increase, decrease, or no change.) (a) Adding N2O(g) to the system. (b) Removing O2(g). (c) Increasing the volume of the container. (d) Adding a catalyst. 2. For the following reaction, ΔH = 2816 kj: 6 CO 2 (g) + 6 H 2 O(l) C 6 H 12 O 6 (s) + 6 O 2 (g) Which of the following statements about this equilibrium are true? A. Increasing P CO2 will cause it to shift to the left. B. Increasing temperature will cause it to shift to the left. C. Decreasing the total pressure at constant temperature will have no effect. D. Removing part of the C 6 H 12 O 6 will cause it to shift to the right. E. Adding a catalyst will cause it to shift to the left. Class 14 Page 7 Group Work