132 CHEM S'09 Exam 2 1. Write the expression for KC for the reaction of acetate ion with water: CH3CO2(aq) + H2O(l) CH3CO2H(aq) + OH(aq)
a. KC =
b. KC =
c. KC =
[CH 3CO 2H][OH ]
[CH 3CO 2 ]
d. KC =
e. KC =
2. Which of the following statements are correct ? 1. Product concentrations appear in the numerator of an equilibrium constant expression. 2. A reaction favors the formation of products if K >> 1. 3. Equilibrium constants have units of atmospheres for gas phase reactions. a. b. c. d. e. 1 only 2 only 3 only 1 and 2 1, 2, and 3
3. Write a balanced chemical equation which corresponds to the following equilibrium constant expression. Kp =
a. b. c. d. e.
1/2 N2(g) + 3/2 H2(g) NH3(g) N2(g) + 3 H2(g) 2 NH3(g) 2 NH3(g) N2(g) + 3 H2(g) NH3(g) 1/2 N2(g) + 3/2 H2(g) 2 N2(g) + 6 H2(g) 4 NH3(g)
4. For which one of the following reactions does Kp equal Kc? a. b. c. d. e. 2 SO2(g) + O2(g) 2 SO3(g) 2 O3(g) 3 O2(g) 2 Ag2O(s) 4 Ag(s) + O2(g) 2 NH3(g) 3 H2(g) + N2(g) CO(g) + NO2(g) NO(g) + CO2(g)
5. The following reaction is studied at a high temperature: PCl5(g) PCl3(g) + Cl2(g) At equilibrium, the partial pressures of the gases are as follows: PCl5 = 1.8 102 atm, PCl3 = 5.6 102 atm, and Cl2 = 3.8 104 atm. What is the value of Kp for the reaction? a. b. c. d. e. 3.8 107 1.2 103 3.1 8.5 102 2.6 106
6. We place 0.0774 mol N2O4(g) in a 1.00 L flask at a given temperature. After reaching equilibrium, the concentration of NO2(g) is 0.0068 M. What is Kc for the reaction: N2O4(g) 2 NO2(g) a. b. c. d. e. 8.8 105 5.9 104 6.2 104 7.2 104 9.6 102
7. At 2000 C, the following reaction has Kc = 4.0 104:
N2(g) + O2(g) 2 NO(g)
If the equilibrium concentrations of N2 and O2 are 0.28 mol/L and 0.38 mol/L at 2010 K, what is the equilibrium concentration of NO? a. b. c. d. e. 1.8 109 M 2.1 105 M 4.3 105 M 6.5 103 M 6.1 102 M
8. Hydrogen iodide can decompose into hydrogen and iodine:
2 HI(g) H2(g) + I2(g)
Kp = 0.016
If 0.820 atm HI(g) is sealed in a flask, what is the pressure of each gas when equilibrium is established? a. b. c. d. e. HI = 0.576 atm, H2 = 0.096 atm, I2 = 0.096 atm HI = 0.654 atm, H2 = 0.083 atm, I2 = 0.083 atm HI = 0.728 atm, H2 = 0.092 atm, I2 = 0.092 atm HI = 0.737 atm, H2 = 0.083 atm, I2 = 0.083 atm HI = 0.768 atm, H2 = 0.111 atm, I2 = 0.111 atm
9. For the following reaction:
2 SO2(g) + O2(g) 2 SO3(g)
Kp = 0.758 at 627 C. SO3(g) SO2(g) + 1/2 O2(g)
What is the equilibrium constant, Kp, at 627 C, for the reaction: a. b. c. d. e. 0.660 0.871 1.15 1.32 1.74
10. Assume the following reaction is at equilibrium at 25 C. If the temperature is decreased to 5 C, which is true? a. b. c. d. e.
I2(g) + Cl2(g) 2 ICl(g)
H = 26.9 kJ
Kp will decrease and the reaction will shift in the forward direction. Kp will decrease and the reaction will shift in the backward direction. Kp will remain unchanged and the reaction will shift in the forward direction. Kp will remain unchanged and the reaction will shift in the backward direction. Kp will increase and the reaction will shift in the forward In direction.
11. which of the following equilibrium systems will an increase in the pressure have NO effect on the concentrations of products and reactants? a. b. c. d. e. CaO(s) + CO2(g) CaCO3(s) N2(g) + 3 H2(g) 2 NH3(g) H2(g) + Cl2(g) 2 HCl(g) H2(g) + CO2(g) CO(g) + H2O(l) 2 H2O2(g) 2 H2O(g) + O2(g)
12. According to the BrnstedLowry definition, an acid a. b. c. d. e. increases the H3O+ concentration in an aqueous solution. increases the OH concentration in an aqueous solution. is a proton acceptor. is a proton donor. is an electron pairacceptor.
13. In the following reaction: a. b. c. d. e. HCO3 is an acid and H2O is its conjugate base. HCO3 is an acid and CO32 is its conjugate base. H3O+ is an acid and HCO3 is its conjugate base. H2O is an acid and CO32 is its conjugate base. H3O+ is an acid and CO32 is its conjugate base.
HCO3(aq) + H2O(l)
CO32(aq) + H3O+(aq)
14. Which one of the following is NOT an amphiprotic species in water ? a. b. c. d. e. HC2O4 CH3CO2 HPO42 H2PO4 HCO3
15. The conjugate acid of HSO4 is ____. a. b. c. d. e. OH SO42 H2SO4 H2O H3O+
16. A solution is prepared combining 0.16 mol of nitric acid, HNO3, with enough water to make 1.5 L. What is the pH of this solution? a. b. c. d. e. 0.80 0.80 0.97 1.83 2.24
17. What is the OH concentration of an aqueous solution with a pH of 11.45? a. b. c. d. e. 3.5 1012 M 9.4 1010 M 1.1 105 M 2.8 103 M 7.8 102 M
18. Which of the following chemical equations corresponds to the base ionization constant, Kb, for the nitrite ion (NO2) ? a. b. c. d. e. HNO2(aq) + H2O(l) NO2(aq) + H3O+(aq) NO2(aq) + H2O(l) HNO2(aq) + OH(aq) HNO2(aq) + OH(aq) NO2(aq) + H2O(l) NO2(aq) + OH(aq) HNO32(aq) NO2(aq) + H3O+(aq) HNO2(aq) + H2O(l)
19. Boric acid, has a pKa value of 9.14. What is Kb for the conjugate base of boric acid? a. b. c. d. e. 7.2 1010 1...