Review 10: Equilibrium

AP chem Text: chapters 13, 15 • • Kp = Kc(RT) ICE charts Δ 3. 4. Name: ____________________ n PROBLEMS 1. Some PCl3(g) and Cl2(g) are mixed o in a container at 200 C and the system reaches equilibrium according to the equation below. Which of the following cuases an increase in the number of moles of PCl5 at equilibrium? PCl3(g) + Cl2(g) ⇌ PCl5(g) + energy i. Decreasing the volume of the container ii. Raising the temperature iii. Adding a mole of He gas at constant volume a. i only b. ii only c. i and iii only d. ii and iii only e. i, ii, and iii 2. Review - 10 (Equilibrium) A student wishes to reduce the zinc ion concentration in a saturated zinc -6 iodate solution to 1 x 10 M. How many moles of solid KIO3 must be added to 1.00 L of solution? (Ksp = 4 -6 o x 10 for Zn(IO3)2 at 25 C) a. 1 mol b. 0.5 mol c. 0.0001 mol d. 4 mol e. 2 mol At constant temperature, a change in volume will NOT affect the moles of substances present in which of the following? a. H2(g) + I2(g) ⇌ 2HI(g) b. CO(g) + Cl2(g) ⇌ COCl2(g) c. PCl5(g) ⇌ PCl3(g) + Cl2(g) d. N2(g) + 3H2(g) ⇌ 2NH3(g) e. CH4(g) + CO2(g) ⇌ 2CO(g) + 2H2(g) The equilibrium constant for the 2hydrolysis of C2O4 is best represented by which of the following? 2a. K = [OH ][C2O4 ]/[HC2O4 ] • • b. c. d. e. 5. i. ii. iii. 6. i. ii. iii. 7. + Le Chatelier’s principle Solubility equilibrium, Q vs Ksp 2- - K = [H3O ][C2O4 ]/[HC2O4 ] 2K = [HC2O4 ][ OH ]/[C2O4 ] 2K = [C2O4 ]/[HC2O4 ][OH ] 2+ K = [C2O4 ]/[HC2O4 ][H3O ] C(s) + H2O(g) ⇌ CO(g) + H2O(g) is endothermic. An equilibrium mixture of the reactants is placed in a sealed o container at 150 C. The amount of the products may be increased by which of the following changes? Raising the tempreature of the container Increasing the volume of the container Adding 1 mol of C(s) to the container f. ii only g. i and ii h. i only i. ii and iii j. iii only C2H4(g) + 3O2(g) ⇌ 2CO2(g) + 2H2O(g). An equimolar number of moles of each of the reactants are sealed in a container and allowed to come to the equilibrium shown above. At equilibrium, which of the following must be true? [CO2] must be equal to [H2O] [O2] must be less than [C2H4] [CO2] must be greater than [C2H4] a. ii and iii b. i only c. iii only d. ii only e. i and ii CH4(g) + CO2(g) ⇌ 2CO(g) + 2H2(g). A 1.00-L flask is filled with 0.30 mol of CH4 and 0.40 mol of CO2, and allowed to come to equilibrium. At equilibrium, there are 0.20 mol of CO in the flask. What is the value of Kc, the equilibrium constant, for this reaction? a. 1.2 b. 0.027 c. d. e. 0.30 0.060 3.0 8. NO2(g) ⇌ 2NO(g) + O2(g). The above materials were sealed in a flask and allowed to come to equilibrium at a certain temperature. A small quantity of O2(g) was added to the flask, and the mixture allowed to return to equilibrium at the same temperature. Which of the following has increased over its original equilibrium value? a. The quantity of NO2(g) present b. The quantity of NO(g) present c. The equilibrium constant, K d. The rate of the reaction e. The partial pressure of NO(g) 9. 2CH4(g) + O2(g) ⇌ 2CO(g) + 4H2(g) ΔH < 0. In order to increase the value of the equilibrium constant, K, which of the following changes must be made to the above equilibrium? a. Increase the temperature b. Increase the volume c. Decrease the temperature d. Add CO(g) e. Add a catalyst 10. The addition of nitric acid increases the solubility of which of the following compounds? a. KCl(s) b. Pb(CN)2(s) c. Cu(NO3)2(s) d. NH4NO3(s) e. FeSO4(s) -13 11. The Ksp for Mn(OH)2 is 1.6 x 10 . What is the molar solubility of this compound in water? -14 1/3 a. (4.0 x 10 ) -13 b. 1.6 x 10 -13 1/3 c. (4.0 x 10 ) -14 1/2 d. (4.0 x 10 ) -14 e. 4.0 x 10 © S. O’Malley 2012 FREE-RESPONSE 212. An aqueous solution is prepared that is initially 0.100 M CdI4 . After equilibrium is established, the solution is found 2+ to be 0.013 M in Cd . 2- 2+ - CdI4 (aq) ⇌ Cd (aq) + 4I (aq) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. A E A C B E B A C B A a. Derive the expression for the dissociation constant and determine the value of the constant. b. What will be the cadmium ion concentration arising when 0.400 mol of KI is added to 1.00 L of the solution in part a? c. A solution is prepared by mixing 0.500 L of the solution from part b and 0.500 L of 2.0 x 10 M NaOH. Will the -14 cadmium hydroxide, Cd(OH)2, precipitate? The Ksp for cadmium hydroxide is 2.2 x 10 . d. When the initial solution is heated, the cadmium ion concentration increases. Is the equilibrium an exothermic or an endothermic process? Explain how you arrived at your conclusion. -5 11. a. Ksp = [Cd2+][I-]4 / [CdI42-] = 1.1 x 10-6 b.[Cd2+] = x = 4.3 x 10-6 M c. Q = 2.2 x 10-16 < Ksp, so it will NOT precipitate. d. Since the cadmium ion concentration increases, the equilibrium shifts right. Thus heat is added and the reaction is endothermic. Problems taken from “5 Steps to a 5”, McGraw Hill