Equilibrium Multiple Choice

Equilibrium Multiple Choice January 1999 7. Consider the following graph: When equilibrium is reached, the rate of the forward reaction is A. 0.00 mol/min B. 0.25mol/min C. 1.0 mol/min D. 3.0 mol/min 8. Consider the following equilibrium: 2NO 2 (g) N 2 O 4 (g) + energy The equilibrium will shift to the left as a result of A. adding a catalyst. B. increasing the volume. C. removing some N 2 O 4. D. decreasing the temperature. 9. Ethene, C 2 H 4, can be produced in the following industrial system: C 2 H 6 (g) + energy C 2 H 4 (g) + H 2 (g) The conditions that are necessary to maximize the equilibrium yield of C 2 H 4 are A. low temperature and low pressure. B. low temperature and high pressure. C. high temperature and low pressure. D. high temperature and high pressure.

10. Consider the following equilibrium: H 2 (g) + I 2 (g) 2HI (g) The volume of the equilibrium system is increased and a new equilibrium is established. Compared to the rates in the original equilibrium, which of the following describes the rates of the forward and reverse reactions in the new equilibrium? 11. Consider the following equilibrium: N 2 (g) + 3H 2 (g) 2NH 3 (g) + energy Certain conditions provide less than 10% yield of NH3 at equilibrium. Which of the following describes this equilibrium? 12. Which of the following best describes the relationship between K eq and temperature for an endothermic reaction?

April 1999 7. Consider the following PE diagram for a reversible reaction: Which of the following describes this reaction? 8. Consider the following equilibrium: 2NO (g) + Br 2(g) + energy The equilibrium will shift to the left as a result of 2NOBr (g) A. adding a catalyst. B. removing NOBr. C. increasing the volume. D. increasing the temperature. 9. Consider the following equilibrium: N 2(g) + O 2(g) + energy When the temperature is increased, the equilibrium shifts to the A. left and K eq increases. B. left and K eq decreases. C. right and K eq increases. D. right and K eq decreases. 2NO (g)

10. Consider the following equilibrium: 2CO (g) + O 2(g) 2CO 2 (g) + energy Some CO 2 is added to the equilibrium system at constant volume and a new equilibrium is established. Compared to the original equilibrium, the rates of the forward and reverse reactions for the new equilibrium have 11. An indication that an equilibrium system favours the products is a A. large K eq. B. positive H. C. one step mechanism. D. low activation energy. 12. The relationship between K eq and the pressure of a gaseous equilibrium at constant temperature can be described by 13. Consider the following equilibrium: 2NO 2(g) N 2 O 4(g) A 1.00 L flask contains 0.030 mol NO 2 and 0.040 mol N 2 O 4 at equilibrium. The value of K eq is A. 0.023 B. 0.67 C. 1.3 D. 44

June 1999 7. Consider the following reaction: N 2(g) + 3H 2(g) 2NH 3 (g) + energy Which of the following describes the changes in enthalpy and entropy as the reaction proceeds? 8. Consider the following equilibrium: 2SO 2(g) + O 2(g) 2SO 3(g) + energy Which of the following will cause this equilibrium to shift to the left? A. adding a catalyst B. adding some SO 2 C. increasing the volume D. decreasing the temperature 9. Methanol, CH 3 OH, can be produced by the following: CO (g) + 2H 2(g) CH 3 OH(g) + energy The conditions that are necessary to maximize the equilibrium yield of CH 3 OH are A. low temperature and low pressure. B. high temperature and low pressure. C. low temperature and high pressure. D. high temperature and high pressure. 10. A catalyst is added to a system already at equilibrium. How are the forward and reverse reaction rates affected by the addition of the catalyst?

11. Consider the following reaction: 2H 2(g) + O 2(g) 2H 2 O (l) What is the equilibrium constant expression for the reaction? A. Keq = [H 2 ] 2 [O 2 ] [H 2 ] 2 [O 2 ] B. Keq= --------------- [H 2 O] 2 [H 2 O] 2 C. Keq= --------------- [H 2 ] 2 [O 2 ] 1 D. Keq= ------------------ [H 2 ] 2 [O 2 ] 12. The relationship between K eq and temperature for an exothermic reaction is represented by 13. Consider the following equilibrium: 2NOBr (g) 2NO (g) + Br 2(g) K eq = 6.4 X 10-2 At equilibrium, a 1.00 L flask contains 0.030 mol NOBr and 0.030 mol NO. How many mol Br 2 are present? A. 1.9 10 3 mol B. 6.4 10 2 mol C. 3.0 10 2 mol D. 4.7 10 1 mol

August 1999 7. At different conditions, the relationship between the forward and reverse rates of reaction in an equilibrium system can be represented by 8. Consider the following equilibrium: 4NH 3(g) + 5O 2(g) 4NO (g) + 6H 2 O (g) + energy Which of the following will cause the equilibrium to shift to the left? A. adding H 2 O (g) B. removing some NO (g) C. increasing the volume D. decreasing the temperature 9. Consider the following equilibrium: 2NO (g) + O 2(g) 2NO 2 (g) + energy When the volume of the container is increased, the equilibrium shifts to the A. left and K eq decreases. B. right and K eq increases. C. left and Keq remains constant. D. right and Keq remains constant.

10. Consider the following equilibrium: 4HCl (g) + O 2(g) 2H 2 O (g) + 2Cl 2 (g) + energy The temperature of the equilibrium system is increased and a new equilibrium is established. The rates of the forward and reverse reactions for the new equilibrium compared to the original equilibrium have 11. Consider the following reaction: 2Hg (g) + O 2(g) 2HgO (s) The equilibrium constant expression for the reaction is 12. The value of Keq changes when A. a catalyst is added. B. the temperature changes. C. the surface area changes. D. the concentration of reactants changes. 13. Consider the following equilibrium: PCl 5(g) PCl 3(g) + Cl 2(g) A 1.00 L flask contains 0.0200 mol PCl 5, 0.0500 mol PCl 3 and 0.0500 mol Cl 2 at equilibrium. The value of K eq is A. 0.125 B. 2.50 C. 5.00 D. 8.00

January 2000 7. Consider the following equilibrium: N 2(g) + 2O 2(g) 2NO 2(g) Equal moles of N 2 and O 2 are added, under certain conditions, to a closed container. Which of the following describes the changes in the reverse reaction which occur as the system proceeds toward equilibrium? 8. A chemical equilibrium is described as dynamic because A. maximum randomness has been achieved. B. the pressure and temperature do not change. C. both reactants and products continue to form. D. the concentrations of chemical species remain constant. 9. Which of the following reactions results in an entropy increase? A. 2C (s) + O 2(g) 2CO (g) B. N 2(g) + 2H 2(g) N 2 H 4(l) C. 2SO 2(g) + O 2(g) 2SO 3(g) D. Ag + (aq) + Cl - (aq) AgCl (s) 10. Consider the following equilibrium: CH 3 COOH (aq) + H 2 O (l) CH 3 COO - (aq) + H 3 O + (aq) + heat A stress was applied at time t 1 and the data was plotted on the following graph: The stress that was imposed at time t 1 is the result of A. the addition of HCl. B. decreasing the temperature. C. the addition of NaCH 3 COO. D. increasing the volume of the container.

11. Consider the following potential energy diagram for an equilibrium system: When the temperature of the system is increased, the equilibrium shifts to the A. left and the K eq increases. B. left and the K eq decreases. C. right and the K eq increases. D. right and the K eq decreases. 12. What is the Keq expression for the following equilibrium? 3Fe (s) + 4H 2 O (g) Fe 3 O 4(s) + 4H 2(g) 13. Consider the following equilibrium: 2O 3(g) 3O 2(g) Keq= 65 Initially, 0.10 mole of O 3 and 0.10 mole of O 2 are placed in a 1.0L container. Which of the following describes the changes in concentrations as the reaction proceeds toward equilibrium?

April 2000 7. Which of the following applies to a chemical equilibrium? I. Forward and reverse reaction rates are equal II. Equilibrium can be achieved from either direction III. Macroscopic properties are constant A. I only B. I and II only C. II and III only D. I, II and III 8. In which of the following will the driving forces of minimum enthalpy and maximum entropy oppose one another? A. 2C (s) + O 2(g) 2CO (g) H= -221kJ B. 2N 2(g) + O 2(g) 2N 2 O (g) H= +164kJ C. 2CO (g) + O 2(g) 2CO 2(g) H= -566kJ D. 2CO 2(g) + 6H 2 O (g) 2C 2 H 6(g) + 7O 2(g) H= +3122kJ 9. Consider the following equilibrium: 2CrO 2-4 (aq) + 2H 3 O + (aq) (yellow) Cr 2 O 2-7 (aq) + 3H 2 O (l) (orange) An unknown solution is added to an orange equilibrium sample until the sample turns yellow. The unknown solution could be A. KNO 3 B. NaOH C. NH 4 NO 3 D. CH 3 COOH 10. Ammonia, NH 3, is produced by the following reaction: N 2(g) + 3H 2(g) 2NH 3(g) + energy Which of the following would result in the highest concentration of ammonia at equilibrium? A. increasing the temperature and increasing the pressure B. decreasing the temperature and increasing the pressure C. increasing the temperature and decreasing the pressure D. decreasing the temperature and decreasing the pressure

11. What is the Keq expression for the following reaction? SnO 2(s) + 2CO (g) Sn (s) + 2CO 2(g) 12. Consider the following reaction: C (s) + 2H 2(g) CH 4(g) H = -74.8KJ Which of the following will cause an increase in the value of Keq? A. increasing [H 2 ] B. decreasing the volume C. finely powdering the C (s) D. decreasing the temperature 13. Consider the following equilibrium: H 2(g) + I 2(g) 2HI (g) At equilibrium [H 2 ] = 0.00220 mol/l, [I 2 ] = 0.00220 mol/l and [HI] = 0.0156mol/L. The value of Keq is A. 3.10 X 10-4 B. 1.99 X 10-2 C. 5.03 X 10 1 D. 3.22 X 10 3 June 2000 7. Consider the following equilibrium: 2NOCl (g) 2NO (g) + Cl 2(g) A flask of fixed volume is initially filled with NOCl (g), NO (g) and Cl 2(g). When equilibrium is reached, the pressure has increased. To reach equilibrium, the reaction proceeded to the A. left because Trial K eq was less than Keq. B. right because Trial K eq was less than K eq. C. left because Trial K eq was greater than Keq. D. right because Trial K eq was greater than Keq.

8. In which of the following do both minimum enthalpy and maximum entropy factors favour the reactants? A. Cl 2(g) Cl 2(aq) H = -25 kj B. C (s) + H 2 O (l) CO (g) + H 2(g) H = +131kJ C. 2CO 2(g) + 3H 2 O (g) C 2 H 5 OH (l) + 3O 2 H = +1239kJ D. Na 2 CO 3(s) + HCl (aq) 2NaCl (aq) + CO 2(g) + H 2 O (l) H = -28kJ 9. Consider the following equilibrium: H 2 (g) + I 2(g) 2HI (g) Which graph represents what happens when some HI is removed and a new equilibrium is established? 10. Consider the following equilibrium: CO (g) + H 2 O (g) CO 2(g) + H 2(g) H= -41kJ What will cause a shift in the equilibrium? A. adding a catalyst B. changing volume C. adding an inert gas D. changing temperature 11. The equilibrium expression for a reaction is [H + ] 6 Keq = ------------------- [Bi 3+ ] 2 [H 2 S] 3 The reaction could be A. 6H + + BiS (s) 2Bi 3+ (aq) + 3H 2 S (g) B. 6H + (aq) + Bi 2 S 3 (s) 2Bi 3+ (aq) + 3H 2 S (g) C. 2Bi 3+ (aq) + 3H 2 S (aq) Bi 2 S 3(s) + 6H + (aq) D. 2Bi 3+ (aq) + 3H 2 S (aq) Bi 2 S 3 (aq) + 6H + (aq)

12. Consider the following equilibrium: Co(H 2 O) 2+ 6 (aq) + 4Cl - 2- CoCl 4 (aq) + 6H 2 O (l) (pink) (blue) When the temperature is increased, the solution turns a dark blue. Based on this observation, the reaction is A. exothermic and the Keq has increased. B. exothermic and the Keq has decreased. C. endothermic and the Keq has increased. D. endothermic and the Keq has decreased. 13. Consider the following equilibrium: 2O 3(g) 3O 2(g) Keq = 36 What is the concentration of O 3 when the equilibrium concentration Of O 2 is 6.0 X 10-2 mol/l? A. 2.4 X 10-3 mol/l B. 4.0 X 10-2 mol/l C. 6.0 X 10-2 mo/l D. 9.0 X 10-2 mol/l August 2000 7. Which of the following does not apply to all chemical equilibrium systems? A. They are closed. B. The macroscopic properties are constant. C. Forward and reverse reaction rates are equal. D. There are equal concentrations of reactants and products. 8. Consider the following equilibrium: 2NOCl (g) 2NO (g) + Cl 2(g) A flask is filled with NOCl, NO and Cl 2. Initially there was a total of 5.0 moles of gases present. When equilibrium is reached, there is a total of 6.0 moles of gases present. Which of the following explains this observation? A. The reaction proceeded left because the Trial Keq > Keq B. The reaction proceeded left because the Trial Keq < Keq C. The reaction proceeded right because the Trial Keq > Keq D. The reaction proceeded right because the Trial Keq < Keq

9. Consider the following reaction: C 3 H 8 (g) + 5O 2(g) 3CO 2(g) + 4H 2 O (g) Which of the following applies to the forward reaction? H = -2202kJ Entropy Enthalpy A. increases increases B. increases decreases C. decreases increases D. decreases decreases 10. Consider the following equilibrium: 2NO 2(g) N 2 O 4 (g) + energy The number of moles of NO 2 at equilibrium could be increased by A. adding N 2 O 4 B. adding a catalyst. C. decreasing the temperature. D. decreasing the volume by increasing the pressure. 11. What is the Keq expression for Sb 3+ (aq) + Cl - (aq) + H 2 O (l) SbOCl (s) + 2H + (aq) 12. Consider the following equilibrium: H 2 (g) + I 2(g) 2HI (g) Keq = 50.0 What is the value Keq for the reaction rewritten as: 2HI (g) H 2(g) + I 2(g) Keq =? A. 50.0 B. 0.0200 C. 25.0 D. 50.0

13. Consider the following equilibrium: 2NO 2(g) N 2 O 4 (g) Keq = 1.15 The equilibrium concentration of NO 2 is 0.50 mol/l. Calculate the equilibrium Concentration of N 2 O 4 (g). A. 0.22 mol/l B. 0.29 mol/l C. 0.43 mol/l D. 0.58 mol/l January 2001 7. All chemical equilibriums have: I. rates that are continuing to change II. an equilibrium constant expression III. equal concentrations of products and reactants A. II only B. III only C. I and II only D. I and III only 8. From the following, select the situation where both enthalpy and entropy favour the reaction toward products: Enthalpy Entropy A. increasing increasing B. increasing decreasing C. decreasing decreasing D. decreasing increasing 9. Consider the following equilibrium: 2NO (g) + Br 2(g) 2NOBr (g) + energy The equilibrium will shift to the left as a result of A. adding a catalyst. B. adding some NO (g). C. increasing the volume. D. decreasing the temperature.

10. Consider the following equilibrium: PCl 3(g) + 3NH 3(g) P(NH 2 ) 3 (g) + 3HCl (g) The volume of the equilibrium system is increased and a new equilibrium is established. How have the rates been affected? Rate (forward) Rate (reverse) A. increased decreased B. decreased increased C. decreased decreased D. did not change did not change 11. Starting with equal moles of reactants, which of the following equilibrium systems most favours the reactants? A. SO 2(g) + NO 2(g) SO 3 (g) + NO (g) Keq= 3.4 B. CO (g) + H 2 O (g) CO 2(g) + H 2(g) Keq= 31.4 C. H 2(g) + I 2(g) 2HI (g) Keq= 10 D. N 2 (g) + O 2(g) 2NO (g) Keq= 1.0X10-31 12. Consider the following equilibrium reaction: N 2 O 4(g) 2NO 2(g) At time t 1, heat is applied to the system. Which of the following best describes the equilibrium reaction and the change in Keq? A. exothermic and Keq increases B. exothermic and Keq decreases C. endothermic and Keq increases D. endothermic and Keq decreases

13. Consider the following: PCl 3(g) + Cl 2(g) PCl 5(g) Keq = 0.45 at 227 C Initially, a 1.00L flask is filled with 0.100mol PCl 3, 0.100mol Cl 2, and 0.100mol PCl 5 at 227 C. Use K Trial to predict the change in [Cl 2 ] as equilibrium is established. April 2001 7. Consider the following equilibrium reaction: 2ICl (g) I 2(g) + Cl 2(g) Some ICl is added to an empty flask. How do the reaction rates change as the system approaches equilibrium? Forward rate Reverse rate A. increases increases B. increases decreases C. decreases increases D. decreases decreases 8. In an equilibrium system, continuing microscopic changes indicate that the equilibrium is A. dynamic. B. complete. C. exothermic. D. spontaneous. 9. Consider the following equilibrium: 4CuO (s) + energy The equilibrium will shift to the right as a result of 2Cu 2 O (s) + O 2(g) A. adding CuO (s). B. removing O 2 (g). C. adding a catalyst. D. decreasing the temperature.

10. Consider the following equilibrium: N 2(g) + 3H 2(g) 2NH 3(g) The volume of the system is decreased. The equilibrium shifts A. left since the reverse rate is greater than the forward rate. B. left since the forward rate is greater than the reverse rate. C. right since the reverse rate is greater than the forward rate. D. right since the forward rate is greater than the reverse rate. 11. Consider the following equilibrium: 2SO 3(g) 2SO 2(g) + O 2(g) Η = +198kJ When the temperature is increased, the equilibrium will shift A. left with Keq becoming larger. B. right with Keq becoming larger. C. left with Keq becoming smaller. D. right with Keq becoming smaller. 12. Starting with equal concentrations of reactants, which of the following will be closest to completion at equilibrium? A. CO (g) + Cl 2(g) COCl 2(g) Keq=22 B. PCl 3(g) + Cl 2(g) PCl 5(g) Keq= 2.9 X 10-2 C. CO (g) + Cl 2(g) COCl 2(g) Keq=4.5 X 10 9 D. CH 3 O 2 (g) + NO 2(g) CH 3 O 2 NO 2(g) Keq=2.1 X 10-12 13. Consider the following equilibrium: 2COF 2(g) CO 2(g) + CF 4(g) At equilibrium, a 1.00L container contains 7.07 X 10-4 mol COF 2, 1.00 X 10-3 mol CO 2, and 1.00 X 10-3 mol CF 4. What is the value of Keq? A. 7.07 X 10-4 B. 1.41 X 10-3 C. 0.500 D. 2.00

June 2001 7. Consider the following reaction: 2ICl (g) I 2(g) + Cl 2(g) A closed container is initially filled with ICl (g). What are the changes in the rate of the forward reaction and [I 2 ], as the system approaches equilibrium? 8. The entropy of a system is a term used to describe A. randomness. B. heat content. C. average kinetic energy. D. stored chemical energy. 9. Consider the following equilibrium: Cu 2+ (aq) + 4Br - (aq) + energy CuBr 2-4 (aq) Blue colourless green Which of the following will cause this equilibrium to change from blue to green? A. adding NaBr (s) B. adding NaNO 3 (s) C. adding a catalyst D. decreasing the temperature 10. Consider the following equilibrium: Ni (s) + 4CO (g) Ni(CO) 2(l) Η = 160.8kJ Which of the following will cause this equilibrium to shift to the left? A. add some CO B. decrease the volume C. remove some Ni(CO) 4 D. increase the temperature

11. Consider the following equilibrium: N 2 O 4(g) + energy 2NO 2(g) Which of the following shows the relationship between concentration and time as a result of adding a catalyst at time t = 1? 12. Consider the following equilibrium: H 2 S (g) + I 2(g) 2HI (g) + S (s) What is the equilibrium expression for this reaction? [HI] 2 A Keq=--------------- [H 2 S] [H 2 S] B. Keq=--------------- [HI] 2 [HI] 2 [S] C. Keq=--------------- [H 2 S]P[I 2 ] [H 2 S]P[I 2 ] D. Keq=--------------- [HI] 2 [S] 13. Consider the following equilibrium: CO (g) + H 2 O (g) CO 2(g) + H 2(g) Keq = 5.0 At equilibrium, the [CO]= 0.20mol/L, [H 2 O]= 0.30mol/L, and [H 2 ]= 0.90mol/L. Calculate the equilibrium [CO 2 ]. A. 0.013 mol/l C. 0.33 mol/l B. 0.066 mol/l D. 1.0mol/L

14. Consider the following: CO 2(g) + CF 4(g) 2COF 2(g) Keq= 0.50 In a reaction container the initial concentrations are: [CO 2 ]= 0.50mol/L, [CF 4 ]= 0.50mol/L, [COF 2 ]= 0.30 mol/l To reach equilibrium, the reaction will proceed A. left since Trial Keq < K eq B. left since Trial Keq > K eq C. right since Trial Keq < K eq D. right since Trial Keq > K eq August 2001 7. All chemical equilibriums must have A. Keq = 1 B. [reactants]=[products]. C. rate forward = rate reverse. D. mass of reactants = mass of products. 8. Consider the following equilibrium reaction: 4HCl (g) + O 2(g) 2H 2 O (g) + 2Cl 2(g) + 111.4kJ For the forward reaction, how do enthalpy and entropy change? Enthalpy Entropy A. increases decreases B. decreases decreases C. increases increases D. decreases increases 9. Consider the following equilibrium: CH 3 Cl (aq) + OH - (aq) CH 3 OH (aq) + Cl - (aq) The equilibrium will shift to the left as a result of the addition of A. HNO 3 B. KNO 3 C. NaOH D. CH 3 Cl

10. Consider the following equilibrium at 25 C : For this reaction A. Keq = [CO] 4 1 B. Keq= -------------- [CO] 4 Ni (s) + 4CO (g) Ni(CO) 4(l) [Ni(CO) 4(l) ] C. Keq= ---------------- [CO] 4 [Ni] [Ni(CO) 4(l) ] D. Keq= ---------------- [CO] 4 11. Consider the following equilibrium: 2COF 2(g) CO 2(g) + CF 4(g) Keq=2.00 At equilibrium, [CO 2 ]=0.050mol/L and [CF 4 ]=0.050mol/L. What t is [COF 2 ] at equilibrium? A. 0.0012 mol/l B. 0.035 mol/l C. 0.050 mol/l D. 0.22 mol/l 12. Consider the following equilibrium: H 2 O (g) + Cl 2 O (g) 2HOCl (g) Keq= 0.0900 Initially, a 1.00L flask is filled with 0.100mol of H 2 O, 0.100mol of Cl 2 O and 0.100mol of HOCl. As equilibrium is established, the reaction proceeds to the A. left because K Trial > K eq B. left because K Trial < K eq C. right because K Trial > K eq D. right because K Trial < K eq

January 2002 7. Consider the following: 2SO 2(g) + O 2(g) 2SO 3(g) Initially, SO 3 is added to an empty flask. How do the rate of the forward reaction and [SO 3 ] change as the system proceeds to equilibrium? 8. Consider the following reaction: N 2(g) + 3H 2(g) 2NH 3(g) + energy What positions do minimum enthalpy and maximum entropy tend toward? Use the following equilibrium equation to answer questions 9 and 10. CO 2(g) + H 2(g) H 2 O (g) + CO (g) 9. Which two stresses will each cause the equilibrium to shift to the left? A. increase [H 2 ], increase [CO] B. decrease [H 2 ], increase [H 2 O] C. increase [CO 2 ], decrease [CO] D. decrease [CO 2 ], decrease [H 2 O]

10. Which of the following graphs represents the forward rate of reaction when H 2 O (g) is added to the above equilibrium at time t = 1? 11. Consider the following: 2NH 3 (g) N 2(g) + 3H 2(g) Initially, some NH 3 is placed into a 1.0L container. At equilibrium there is 0.030mol N 2 present. What is the [H 2 ] at this equilibrium? A. 0.010 mol/l B. 0.030 mol/l C. 0.060 mol/l D. 0.090 mol/l 12. Which reaction has the following equilibrium expression? [NO 2 ] 4 [H 2 O] 6 Keq=----------------- [NH 3 ] 4 [O 2 ] 7 A. 4NH 3(g) + 7O 2(g) 4NO 2(g) + 6H 2 O (g) B. 4NH 3(aq) + 7O 2(g) 4NO 2(aq) + 6H 2 O (l) C. 4NO 2(aq) + 6H 2 O (l) 4NH 3(g) + 7O 2(g) D. 4NO 2(g) + 6H 2 O (g) 4NH 3(g) + 7O 2(g) 13. What will cause the Keq for an exothermic reaction to increase? A. increasing [reactants] B. decreasing [products] C. increasing the temperature D. decreasing the temperature

April 2002 7. Consider the following: H 2(g) + I 2(g) 2HI (g) Initially, HI is added to an empty flask. How do the rates of the forward and reverse reactions change as the system proceeds to equilibrium? 8. Consider the following reaction: 2H 2 O (l) + energy 2H 2 (g) + O 2(g) Determine the enthalpy and entropy changes for the above reaction? Use the following equilibrium equation to answer questions 9 and 10. 2CO (g) + O 2(g) 2CO 2(g) + energy 9. Which of the following two stresses will each cause the system to shift to the right? A. increase temperature, increase volume B. decrease temperature, increase volume C. increase temperature, decrease volume D. decrease temperature, decrease volume

10. Which of the following shows the forward rate of reaction when the temperature of the system is increased at time t = 1? 11. Consider the following: 2SO 2(g) + O 2(g) 2SO 3(g) Initially, 0.030mol SO 2 and 0.030mol O 2 are placed into a 1.0L container. At equilibrium, there is 0.020 mol O 2 present. What is the [SO 2 ] at equilibrium? A. 0.010 mol/l B. 0.020 mol/l C. 0.030 mol/l D. 0.040 mol/l 12. What is the equilibrium expression for the following system? CaCO3 (s) + 2HF (g) CaF 2(s) + H 2 O (g) + CO 2(g) [HF] 2 [H 2 O][CO 2 ] A. Keq=-------------------- C. Keq= --------------- [H 2 O][CO 2 ] [CaCO 3 ][HF] 2 [H 2 O][CO 2 ] [CaF2] [H 2 O][CO 2 ] B. Keq=---------------- D. Keq= ---------------------- [HF] 2 [CaCO 3 ][HF] 2 13. What will cause the K eq for an endothermic reaction to decrease? A. adding a catalyst B. increasing the surface area C. increasing the temperature D. decreasing the temperature

Answer Key Jan 99 Apr 99 Jun 99 Aug 99 7 C 7 D 7 C 7 A 8 B 8 C 8 C 8 A 9 C 9 C 9 C 9 C 10 A 10 A 10 A 10 A 11 D 11 A 11 D 11 A 12 C 12 D 12 A 12 B 13 C 13 D 13 B 13 A Jan 00 Apr 00 Jun 00 Aug 00 7 A 7 D 7 B 7 D 8 C 8 C 8 C 8 D 9 A 9 B 9 B 9 B 10 C 10 B 10 D 10 A 11 B 11 B 11 C 11 A 12 C 12 D 12 C 12 B 13 B 13 C 13 A 13 B Jan 01 Apr 01 Jun 01 Aug 01 7 A 7 C 7 A 7 C 8 D 8 A 8 A 8 B 9 C 9 B 9 A 9 A 10 C 10 D 10 D 10 B 11 D 11 B 11 C 11 B 12 C 12 A 12 A 12 A 13 A 13 D 13 C 14 C Jan 02 Apr 02 7 D 7 B 8 D 8 C 9 B 9 D 10 C 10 B 11 D 11 A 12 A 12 B 13 D 13 D