NAME: Equilibrium Review Packet - KEY 1. Which of the following statements concerning equilibrium is not true? a) b) c) d) e) A system that is disturbed from an equilibrium condition responds in a manner to restore equilibrium. Equilibrium in molecular systems is dynamic, with two opposing processes balancing one another. The value of the equilibrium constant for a given reaction mixture is the same regardless of the direction from which equilibrium is attained. A system moves spontaneously toward a state of equilibrium. The equilibrium constant is independent of temperature. 2. Which of the following statements is true? a) b) c) d) e) When two opposing processes are proceeding at identical rates, the system is at equilibrium. Catalysts are an effective means of changing the position of an equilibrium. The concentration of the products equals that of reactants and is constant at equilibrium. An endothermic reaction shifts toward reactants when heat is added to the reaction. None of the above statements is true. 3. Indicate the mass action expression for the following reaction: 2X(g) + Y(g) a) 3W(g) + V(g) [X]2[Y][W]3[V] c) b) d) 4. If, at a given temperature, the equilibrium constant for the reaction H2(g) + Cl2(g) 2HCl(g) is Kp, then the equilibrium constant for the reaction HCl(g) (1/2) H2(g) + (1/2)Cl2 (g) can be represented as: a) b) Kp2 c) d) K.1 102 d) 2. is dependent on 6–7. It is not dependent on any of the above choices. If the concentration of the product were to double. Determine the equilibrium constant for the system N2O4 2NO2 at 25C. It would quadruple its value.4 10–4 b) 2. The –2 concentrations are shown here: [N2O4] = 9.6 10–3 M b) 6. a) d) e) I. d) They are much bigger. If an equimolar mixture of reactants gives the concentration of the product to be 0. The nature of the reactants and products.69 c) 474 d) 0.5. what would happen to the equilibrium constant? a) b) c) It would double its value. 6. Consider the reaction H2 + I2 2HI whose K = 54. It would depend on the initial conditions of the product.00211 9.0% dissociated according to the equation shown here: 2ONCl 2NO + Cl2 Determine the equilibrium constant.8 10–2 M c) 1.43 10 M. The concentration of the products. 8. III It is dependent on three of the above choices.0224 e) 0. I. 7.150 b) 6.2 102 c) 1. At equilibrium it is 9. They are about the same.50 M at equilibrium. IV COCl2.2 10–3 M . a) 4. Consider the chemical system CO + Cl2 c) III. e) It would not change its value.41 10–2 M a) 0. You can’t tell from the information given. e) They have to be exactly equal. [NO2] = 1. The value of the equilibrium constant .0 K.8 at a high temperature. d) It would become half its current value. The concentration of the reactants. K = 4.1 10–1 10. a) 4.6 109 L/mol. II. III. determine the concentration of the hydrogen.2 10–4 e) 9. II b) II. How do the equilibrium concentrations of the reactants compare to the equilibrium concentration of the product? a) b) c) They are much smaller. The temperature of the system. one mole of gaseous ONCl is placed in a one-liter container. At 500. IV. At equilibrium the pressure of NH3(g) is 1. Consider the following system at equilibrium: N2(g) + 3H2(g) 2NH3(g) + 92. III.3 H2O2(g). III. V.200 atm 0.40 d) 31. a) d) increasing the temperature increasing the volume removing some NH3 removing some N2 I.00 –2(0. IV.00 atm and hydrogen gas at a partial pressure of 0.9 at 763 K.20 atm. A 10.13 I.0-g sample of solid NH4Cl is heated in a 5.20 b) 1.6 10–4 M 11.6 10–2 M e) 1. VIII.0 e) none of these .3 atm c) 1. V.8 1024 2.d) 9. IV.8 1037 9. then the equilibrium constant for 13. Kp.00-L container to 900C.200 atm. VI.3 106 H2O2(g) 2H2O(g) b) e) c) C is 0.574 atm b) e) 0.4 1043 5. III.1 e) 16.2 10–4 14. a) 1.123) 2H2(g) + O2(g) a) d) 4. If the equilibrium constant for A + B 2C 2A + 2B is __________.94 kJ Which of the following changes will shift the equilibrium to the right? I. VII b) e) II. VIII c) 0.436 atm 14. NH4Cl(s) NH3(g) + HCl(g) The equilibrium constant.123 d) 66. Calculate Kp for H2O(g) + O2(g) H2(g) + O2(g) decreasing the temperature decreasing the volume adding some NH3 adding some N2 Kp = 1. What is the partial pressure of I2? a) d) 0.123. V. A particular equilibrium mixture at that temperature contains gaseous HI at a partial pressure of 4. VI. V. VII I. IV.44 c) 2. VII.4 10–13 b) 8.6 10–31 c) 1.74 atm 15. VIII II. VI. using the following data: Kp = 2. for the reaction is: a) 1. II. The reaction H2(g) + I2(g) 2HI(g) has Kp = 45. VIII 12. 0 kJ/mol 17. What is the concentration of B at equilibrium? a) d) 0. the concentration of A is 0. At equilibrium.5. Adding more H2(g) increases the equilibrium constant.00 moles of B are placed in a 6. The proper Keq expression is: a) b) c) d) e) 18.00 moles of A and 3. 2. A(g) + 2B(g) C(g) 19. the concentration of A is 0. At 1273 K the Kp value is 167. At equilibrium.0 atm 2 c) 1. What is the value of K? a) 0. If the pressure on the system is increased by changing the volume.10 atm at this temperature? a) 16.16.589 e) 1. Consider the reaction C(s) + CO2(g) 2CO(g).433 mol/L none of these c) 0.300 mol/L. Consider the following equilibrium: H2(g) + I2(s) 2HI(g) H = +68. 19–20. Consider the reaction: CaCl2(s) + 2H2O(g) CaCl2 2H2O(s) The equilibrium constant for the reaction as written is [CaCl 2 2H 2 O] a) K= d) K = [H2O]2 [CaCl 2 ][H 2 O] 2 b) K= e) K= c) K= [CaCl 2 2H 2 O] [H 2 O] 2 17–18.146 b) 0.253 c) 0. What is the PC O at equilibrium if the PC O is 0.500 mol/L 20.00-L container.300 mol/L 0.600 mol/L b) e) 0. the left side is favored. the right side is favored. For the reaction given below.7 atm b) 2. Which of the following statements about the equilibrium is false? a) b) c) d) e) If the system is heated. This is a heterogeneous equilibrium. Removing HI as it forms forces the equilibrium to the right.043 21.300 d) 0.4 atm d) 4.1 atm e) 250 atm .300 mol/L. 82 moles/liter 24. The value for K at 700C for the formation of ammonia is: a) d) 3.10 moles of N2O and 0.0-L container. If the equilibrium constant for the system is 36.9 b) 0.0-liter container and permitted to react at this temperature. The equilibrium lies to the right. .0 moles of NO2 are placed in a 2.25 moles of N2H4.68 moles/liter at 700C. in a 10.39 moles/liter 7.5 liters/mole.0 10–2 b) e) 1. There will be no net gain in either product or reactant. 26. a) d) 0. how many moles of N2 are present at equilibrium? a) 0. The reaction quotient for a system is 7.0 moles of H2(g) were added to a 1. At a certain temperature K for the reaction 2NO2 N2O4 is 7. There will be a net gain in both product and reactant.22.2 102. Which of the following is true for a system whose equilibrium constant is relatively small? a) b) c) d) e) It will take a short time to reach equilibrium.0-liter container and the following reaction then occurred: 3H2(g) + N2(g) 2NH3(g) The equilibrium concentration of NH3(g) = 0.02 e) none of these 23. If 2. The equilibrium lies to the left.0 moles of N2(g) and 4.4 10–1 none of these c) 1.06 moles of N2O at equilibrium. It will take a long time to reach equilibrium. Initially 2. calculate the concentration of N2O4 at equilibrium. The following reaction is investigated (assume an ideal gas mixture): 2N2O(g) + N2H4(g) 3N2(g) + 2H2O(g) Initially there are 0.5 moles/liter b) e) 0. If there are 0.6 10–3 5.1 10–2 25. Two of these.65 moles/liter none of these c) 0. The equilibrium constant will decrease until it equals the reaction quotient.04 c) 0.06 d) 0. what will happen as equilibrium is approached? a) b) c) d) e) There will be a net gain in product. There will be a net gain in reactant. 860. the partial pressure of NOBr was 2.27 c) 0. Which of the following is true about chemical equilibrium? a) It is microscopically and macroscopically static.750 mole of F2(g) are mixed in a 5. none of these 30. d) It is microscopically dynamic and macroscopically static.58 atm 28–29.400 atm d) 0. b) It is microscopically and macroscopically dynamic.246 c) Q = 0.27. a) are infinite is one b) is one are infinite c) is one is one .5 atm. Consider the following reaction: 2HF(g) H2(g) + F2(g) (K = 1. find the equilibrium pressure of the O2 gas if the NO2 gas pressure is 0. a shift in the equilibrium position to the right.0-liter vessel was initially filled with pure NOBr.08 e) none of these 31. c) It is microscopically static and macroscopically dynamic. a) 1. 28.300 atm at equilibrium. For a particular system at a particular temperature there ______ equilibrium constant(s) and there _______ equilibrium position(s).00-L flask. After equilibrium was established.0615 d) Q = 2.520 atm and the PNO is 0. while the temperature was kept at 300 K.45 b) 0. Q.780 atm c) 0. What is Kp for the reaction? a) 0. a) Q = 0.00 mole of HF(g). at a pressure of 4. and 0.00 10–2) Given 1. If the Kp value is 0. 32. a decrease in Kp. e) None of these are true about chemical equilibrium. Consider the following reaction (assume an ideal gas mixture): 2NOBr(g) 2NO(g) + Br2(g) A 1.75 e) none of these 29. Consider the following equilibrated system: 2NO2(g) 2NO(g) + O2(g). determine the reaction quotient. a shift in the equilibrium position to the left. This will result in: a) b) c) d) e) an increase in Kp.990 atm e) 2.328 mole of H2(g). 0.0492 b) Q = 0.49 atm b) 0. at 300 K. After equilibrium was reached.0 atm. the volume was increased to 2.0 liters.18 d) 0. 150 M b) 0.6 10–5 M 4.50 M 36.0 M 4. 33.300 M d) 0.0 10–3 M The questions below refer to the following system: A 3. what is the equilibrium concentration of NO? a) +x b) +2x c) –x e) x2 d) –2x 34.350 M .200 M c) 0. 1.0 10–3 M c) 0.100 M b) 0. Calculate the equilibrium concentration of Cl2(g). Gas A decomposes according to the following reaction: 3A 2B + C The equilibrium concentration of gas C is 0. a) d) 1.450 mol of gas B.100 mol/L.200 M c) 0.d) are infinite 33–36. a) 0. 37.50 M c) 0. what is the equilibrium concentration of Cl 2? a) +x b) + c) 1 + x e) 1 + 2x d) 1 + 35.00 mole of pure NOCl and 1. a) d) 37–39.2 10–4 M b) e) 1. Calculate the equilibrium concentration of NO(g). If x moles of NOCl react. If x moles of NOCl react.500 M e) none of these d) 0.6 10–5.00-liter flask initially contains 1.450 M e) none of these 38. 1.50 mol of gas A and 0.0 M 6. Determine the equilibrium concentration of gas B.00 mole of pure Cl2 are placed in a 1. a) 0.00-L container.2 10–4 M b) e) 1. are infinite e) none of these Consider the following equilibrium: 2NOCl(g) 2NO(g) + Cl2(g) with K = 1. Determine the equilibrium concentration of gas A.6 10–5 M 6. O2. and NO will decrease. Upon adding gas A.08 moles of NO are placed in a 1. Nitric oxide. The concentrations of N2. 0. and 0.4 x 10-1.1 mol of O2. and the concentration of NO will decrease. The concentration of NO will decrease. B. C. K. At 50. A 1-L container originally holds 0. more products are made. At 2000C. The concentration of NO will decrease. increasing the product to reactant ratio.01.53 e) none of these 40–41.0C. K for the reaction N2(g) + O2(g) 2NO(g) is 0. The concentrations of N2. a) b) c) d) e) The system remains unchanged. the value of K is 1. 40. This means that the reaction is .175 c) 0. Predict the direction in which the system will move to reach equilibrium at 2000C if 0. and NO will increase. The concentrations of N2 and O2 will increase.0C the value of K is 3. the concentrations of N 2 and O2 will increase. 41.117 b) 0. decreases because A is a reactant o the product to reactant ratio decreases. is formed from the elements nitrogen and oxygen at high temperatures. You have the gases A. the value of K: a) b) c) d) e) increases because by adding A.5 L without changing the quantities of the gases present.1 moles of O2.227 d) 1. such as those obtained when gasoline burns in an automobile engine. More information is necessary. and NO is decreased to 0. a) 0. the concentrations of N2 and O2 will decrease. There will be no change in the concentrations of N2. For a certain reaction at 25. does not change as long as the temperature is constant.2 x 10-3. and D at equilibrium. Given the reaction A(g) + B(g) C(g) + D(g). O2. Determine the value of the equilibrium constant. how will their concentrations change? a) b) c) d) e) The concentration of NO will increase.39. the concentrations of N2 and O2 will decrease. does not change because A does not figure into the product to reactant ratio. If the volume of the container holding the equilibrium mixture of N2. The concentration of NO will increase.4 moles of N2. 43.0-liter container. the concentrations of N2 and O2 will remain unchanged. and 0. O2.08 mole of NO. 0. 42. O2. depends on whether the reaction is endothermic or exothermic. an important pollutant in air. and NO.4 mol of N2. The Co2+ ions hydrate. e) The solution will become silver-colored. d) Water will be produced. What would happen to the system if oxygen were added? a) b) c) More ammonia would be produced. Which statement below describes the change that the system will undergo if silver nitrate is added (to form silver chloride)? a) b) c) It should become more blue. c) never favorable. b) More information is needed. 47–48. The equilibrium would shift to the left. Two of these. Which statement below describes the change that the system will undergo if hydrochloric acid is added? a) b) c) It should become more blue. It should become more pink. e) None of these (a-d) 44–46. endothermic. The equilibrium will shift to the right. 45. Nothing will change. e) The color will become more blue. d) More water will be produced. 48. There will be less of the hydrated cobalt ion at the new equilibrium position. e) Nothing would happen. What would happen to the system if the pressure were decreased? . The equilibrium will shift to the left.a) d) exothermic. The following questions refer to the equilibrium shown here: 4NH3(g) + 502(g) 4NO(g) + 6H2O(g) 47. The questions below refer to the following system: Cobalt chloride is added to pure water. The equilibrium would shift to the right. d) More oxygen would be produced. Which statement below describes the change that the system will undergo if water is added? a) b) c) More chlorine ions will be produced. The hydrated form then reacts with the Cl– ions to set up the equilibrium shown here: Co(H2O)62+ + 4 Cl– (pink) CoCl42– + 6H2O (blue) 44. The equilibrium will shift to the right. 46. d) e) It should become more pink. Which of the following is true about a system at equilibrium? . Consider the following equilibrium: 2H2(g) + X2(g) 2H2X(g) + energy 49. the reaction to occur to produce H2 but no more X2. will have no effect. When the temperature of the reaction is increased to 500C.a) b) c) d) e) 49–52. e) X2 to dissociate. 52.2 kJ and K (at 25C) = 4. 54. e) an explosion. Increasing the temperature will cause a) b) c) the reaction to occur to produce H2X. Addition of X2 to a system described by the above equilibrium a) b) c) will cause [H2] to decrease. More oxygen would be produced. will cause [H2X] to increase. 50. the reaction to occur to produce H2 and X2. will have no effect. 53.0 108. cannot possibly be carried out. None of the above is true. The NO concentration would increase. d) e) will cause [X2] to decrease. The ammonia concentration would increase. cannot possibly be carried out. will cause [H2X] to decrease. The reaction of N2 with H2 to form ammonia is endothermic. the reaction to occur to produce H2 but no more X2. 51. Nothing would happen. H = –92. d) no reaction to occur. Ammonia is prepared industrially by the reaction: N2(g) + 3H2(g) 2NH3(g) For the reaction. the reaction to occur to produce H2 and X2. The water vapor would become liquid water. d) no reaction to occur. Product formation (at equilibrium) is not favored as the temperature is raised. At equilibrium. d) e) will cause [X2] to increase. which of the following is true? a) b) c) d) e) K for the reaction will be larger at 500C than at 25C. Increasing the pressure by decreasing the volume will cause a) b) c) the reaction to occur to produce H2X. more NH3 is present at 500C than at 25C. Addition of argon to the above equilibrium a) b) c) will cause [H2] to decrease. 3 10–3 M b) 6. a) 8. calculate the equilibrium concentration of chemical C.0010 mol A in a one-liter container. Consider the combustion of methane (as represented by the following equation). K = 1.6 10–2 M none of these c) 1. 55. e) The equilibrium position is shifted but the value for K stays constant.6 104. b) cause [C] to increase.0 M d) 0. 0. The concentration(s) of reactant(s) is constant over time. At a particular temperature. Given the equation 2A(g) 56. None of these (a-d) 58. The rate of the reverse reaction is equal to the rate of the forward reaction and both rates are equal to zero. and 0. which is a source of heat for chemical reactions in the laboratory. d) The equilibrium position is shifted to the left and the value for K increases.a) b) c) d) The concentration(s) of the reactant(s) is equal to the concentration(s) of the product(s).8 10–5. cannot be determined. If you start with 2. CH4(g) + 2O2(g) CO2(g) + 2H2O(g) For the system at chemical equilibrium. To the right. a) d) 6. which direction would the reaction initially proceed? a) b) c) The above mixture is the equilibrium mixture. b) The equilibrium position is shifted to the right and the value for K decreases. . Addition of chemical B to an equilibrium mixture of the above will a) d) cause [A] to increase.0 M of chemical A. This is the reaction that occurs for a Bunsen burner.1 10–2 M b) e) 2.10 mol C.25 10–5 M c) 2.0 10–3 M 2. 56–61.0 M 59.0 mol B. If you mixed 5. If you start with 2. K = 1. calculate the equilibrium concentration of chemical C. which of the following explains what happens if the temperature is raised? a) The equilibrium position is shifted to the right and the value for K increases. c) The equilibrium position is shifted to the left and the value for K decreases. e) none of the above. Cannot tell from the information given.0 M of chemical A. 2B(g) + C(g). At a higher temperature. d) e) To the left.99 M e) none of these 57. c) have no effect. No new product molecules are formed. e) None of the above (a-d) is true. b) cause [B] to increase. d) The amount of SO3(g) decreases and the value for K stays the same. e) none of the above. Consider the reaction represented by the equation 2SO2(g) + O2(g) 2SO3(g). the equilibrium position shifts. cannot be determined. c) The amount of SO3(g) stays the same and the value for K decreases. b) cause [B] to increase. 63. Placing the equilibrium mixture in an ice bath (thus lowering the temperature) will a) d) cause [A] to increase. e) none of the above. 62. Raising the pressure by lowering the volume of the container will a) d) cause [A] to increase. nothing happens to the equilibrium position. d) Nothing happens to the equilibrium position no matter what the container is like.60. c) The equilibrium position shifts no matter what the container is like. b) If the container is rigid. b) The amount of SO3(g) decreases and the value for K increases. nothing happens to the equilibrium position. Consider the reaction represented by the equation N2(g) + 3H2(g) 2NH3(g). e) The value of the equilibrium constant must be known to answer this question. c) have no effect. the equilibrium position shifts. e) The amount of SO3(g) increases and the value for K stays the same. . which of the following explains what happens after the addition of oxygen gas (assume constant temperature)? a) The amount of SO3(g) increases and the value for K increases. If the container is fitted with a moveable piston. 61. What happens to the equilibrium position when an inert gas is added to this system (as represented above) at equilibrium? a) If the container is rigid. If the container is fitted with a moveable piston. For the system at chemical equilibrium. cannot be determined. c) have no effect.