University of Kentucky - Department of Chemistry
24 December 1996
1. For the solid-gas phase equilibrium
I2 (s) = I2 (g) Kp = 0.053 atm at 98oC. Solid I2 (5.00 g, 0.020 mol) is placed in a 1.00-L container and equilibrium is established. What will happen if an additional 1.00 g of solid I2 is placed into the container, with no change in temperature or volume?
A. The pressure in the container will increase. B. The pressure in the container will decrease. C. Some of the added I2 will sublime into the gas phase, but an identical amount of I2 vapor will condense into the solid phase. D. All of the added I2 will sublime into the gas phase.
2. At 200oC, Kc = 4 x 10-18 for the reaction
Br2(g) = 2 Br(g). If one starts with 0.10 mol Br2 in a 2.0 L flask at 200oC, what will the equilibrium system contain?
A. Mostly Br2(g) B. Twice as much Br(g) as Br2(g) C. Half as much Br(g) as Br2(g) D. About equal amounts of Br2(g) and Br(g)
3. At 1500 K, Kc = 1.98 for the gas-phase equilibrium
SO2(g) + NO2(g) = SO3(g) + NO(g). What is Kp for this reaction at 1500 K?
A. 0.0161 B. 123 C. 1.98 D. 243
4. Kp for the reaction
1/2 H2(g) + 1/2 I2(g) = HI(g) is 6.0 at 1200 K. What is Kp at the same temperature for the reaction
2 HI(g) = H2(g) + I2(g) ? A. 0.17 B. 36. C. 2.4 D. 0.028
5. At some temperature, the following partial pressures are measured in a closed reaction vessel in which chemical equilibrium has been reached:PN2 = 0.45 atm PH2 = 0.70 atm PNH3 = 1.30 atm
What is Kp at this temperature for the reaction
N2(g) + 3 H2(g) = 2 NH3(g) ? A. 11 B. 26 C. 0.091 D. 4.6
6. Kp = 0.12 for the reaction
CaCO3(s) = CaO(s) + CO2(g) at 1000 K. What is the final, equilibrium pressure in a sealed 5.0 L flask containing 0.50 mol CaCO3 and 0.25 mol CaO at 1000 K?
A. 0.0015 atm B. 0.12 atm C. 0.24 atm D. 0.06 atm
7. A gaseous mixture contains 0.80 mol SO2Cl2, 0.40 mol SO2 and 0.20 mol Cl2 in a 2.0 L container. At 400 K, Kc = 0.011 for the reaction
SO2(g) + Cl2(g) = SO2Cl2(g) Is the system at equilibrium? If not, which direction will the system shift to achieve equilibrium?
A. The system is at equilibrium. B. More SO2Cl2 will form as the system achieves equilibrium. C. More SO2 and Cl2 will form as the system achieves equilibrium. D. More Cl2, but no more SO2, will form as the system achieves equilibrium.
8. At 1100 K, Kc = 0.55 for the reaction
CO(g) + H2O(g) = CO2(g) + H2(g). If 1.0 mol each of CO(g) and H2O(g) are placed in a 10.0 L container and the system is allowed to come to equilibrium at 1100 K, what is the equilibrium concentration of H2(g)?
A. 0.035 M B. 0.043 M C. 0.24 M D. 0.35 M
9. The reaction
PCl3(g) + Cl2(g) = PCl5(g) is exothermic. Which of these changes would increase the yield of PCl5 (that is, the fraction of PCl3 converted to PCl5) at equilibrium?
A. Decreasing the pressure on the system by increasing the volume of the container. B. Increasing the temperature. C. Adding more Cl2. D. Adding more PCl5.
10. Which of the following changes will decrease the conversion of SO2 to SO3 (i.e., will raise the equilibrium concentration of SO2)?
2 SO2(g) + O2(g) = 2 SO3(g) exothermic (delta H < 0) A. Raising the temperature. B. Decreasing the size of the container. C. Adding more O2. D. Removing SO3.
11. In a 10.0 L flask, 0.110 mol hydrogen and 0.075 mol iodine are combined and heated to 425oC. At equilibrium, 0.140 mol of hydrogen iodide has been produced. What is the equilibrium constant Kc for this reaction?
H2(g) + I2(g) = 2 HI(g) A. 98 B. 2.4 C. 7000 D. 34
12. Which of the following salts is the least soluble (in terms of moles/L) in water?salt Ksp ------------ ----------- Ca(OH)2 7.9 x 10-6 CaCO3 4.8 x 10-9 CaSO4 2.4 x 10-5 CaF2 3.9 x 10-11
A. Ca(OH)2 B. CaCO3 C. CaSO4 D. CaF2
13. What is the solubility of AgCl (Ksp = 1.8 x 10-10) in 0.100 M NaCl?A. 1.3 x 10-5 M B. 1.8 x 10-9 M C. 1.8 x 10-8 M D. 0.90 x 10-9 M
14. Which of these statements is correct?A. A Brønsted-Lowry base is always a hydroxide donor. B. A Brønsted-Lowry base is always a proton donor. C. It is possible for a material to be a Brønsted-Lowry acid in some reactions and a Brønsted-Lowry base in other reactions. D. All Lewis acids are also Brønsted-Lowry acids.
15. Identify a conjugate acid-base pair in this Brønsted-Lowry acid-base reaction:
HBr(aq) + H2O(l) = H3O+(aq) + Br-(aq) Conjugate acid Conjugate base ----------------- --------------- A. Br-(aq) HBr (aq) B. H3O+ (aq) Br- (aq) C. H2O(l) OH- (aq) D. H3O+ (aq) H2O(l)
16. What is the pH of a 2.00 x 10-3 M solution of Ca(OH)2(aq)? Ca(OH)2 is a strong electrolyte.A. 2.70 B. 2.40 C. 11.30 D. 11.60
17. Like water, ammonia (NH3) is an amphoteric substance that can be used as a solvent for acid-base reactions. The phase label (am) means solvated by ammonia (ammoniated). Which statement is correct, extrapolating from your knowledge of acid-base reactions in water?A. Autoionization of ammonia is described by:
2 NH3 (l) = NH4+ (am) + NH2- (am). B. The strongest acid which can exist in ammonia solution is H3O+(am). C. The strongest base which can exist in ammonia solution is NH4+(am). D. The addition of an acid to an ammonia solution will increase the concentration of NH2- (am).
18. If the percent ionization of a 1.0 M solution of acid HA is 30%, what is the Ka of the acid?
HA(aq) + H2O(l) = H3O+(aq) + A-(aq) A. 0.090 B. 9.0 x 102 C. 0.30 D. 0.13
19. What is the pH of a 7.3 x 10-3 M solution of acetic acid, CH3CO2H? Ka = 1.8 x 10-5 for CH3CO2H.A. 1.3 x 10-7 B. 2.14 C. 6.88 D. 3.44
20. Given the data below, calculate Kb for HPO32-.
H2PO3- Ka = 7.0 x 10-7 A. 1.4 x 10-8 B. 7.0 x 107 C. 1.4 x 10-21 D. It cannot be calculated from the information given.
21. Which of the following salts produces an acidic solution when dissolved in water?A. CH3COONa B. CaCl2 C. K2SO4 D. NH4NO3
22. What is the pH of a 1.00 x 10-9 M solution of HNO3?A. pH < 6.50 B. 6.50 < pH < 7.00 C. 7.00 < pH < 7.50 D. pH > 7.50
23. In which of these pairs is the weaker Brønsted acid listed first?A. H2O, NH3 B. H2S, H2O C. H2SO3, H2SO4 D. HCl, HF
24. Which of the following reactions describes a Lewis acid base reaction that is neither an Arrhenius nor a Brønsted-Lowry acid-base reaction?A. 2 HNO3(aq) + CaO(s) ---> Ca(NO3)2(aq) + H2O(aq) B. Zn(OH)2(s) + 2 NaOH(aq) ---> 2 Na+(aq) + Zn(OH)42- (aq) C. HCl(g) + NH3(g) ---> NH4Cl(s) D. HSO4-(aq) + F- (aq) = SO42- (aq) + HF(aq)
25. What is the molar solubility of magnesium hydroxide in an aqueous solution with pH = 12.00? Ksp = 8.9 x 10-12 for Mg(OH)2A. 8.9 x 10-10 M B. 8.9 x 10-8 M C. 3.0 x 10-6 M D. 1.3 x 10-4 M