Chapter 13 Review Questions

General Chemistry: Atoms First, 2e (McMurry and Fay) Chapter 13 Chemical Equilibrium: The Extent of Chemical Reactions 13.1 Multiple Choice Questions 1) Which one of the following statements does not describe the equilibrium state? A) Equilibrium is dynamic and there is no net conversion to reactants and products. B) The concentration of the reactants is equal to the concentration of the products. C) The concentration of the reactants and products reach a constant level. D) The rate of the forward reaction is equal to the rate of the reverse reaction. Answer: B Diff: 1 Topic: Section 13.1 The State of Chemical Equilibrium 2) The equilibrium equation is also known as the law of A) coefficients. B) constant concentration. C) dynamic equilibrium. D) mass action. Answer: D Diff: 1 Topic: Section 13.2 The Equilibrium Constant Kc 3) Which of the following statements is false regarding the equilibrium constant, Kc? A) Kc for a reaction at a particular temperature always has the same value. B) Kc for the reverse reaction is the negative of Kc for the forward reaction. C) The numerical value of Kc depends on the form of the balanced equation. D) When quoting Kc it is customary to omit units. Answer: B Diff: 2 Topic: Section 13.2 The Equilibrium Constant Kc 4) Which statement about the equilibrium constant is true? The value of Kc A) changes as product concentration changes. B) changes as reactant concentration changes. C) changes as temperature changes. D) never changes. Answer: C Diff: 1 Topic: Section 13.2 The Equilibrium Constant Kc 1 Copyright © 2014 Pearson Education, Inc. 5) If Kc is the equilibrium constant for a forward reaction what is Kc' for the reverse reaction? A) -Kc B) Kc C) (Kc)-1 D) none of these Answer: C Diff: 2 Topic: Section 13.2 The Equilibrium Constant Kc 6) If Kc is the equilibrium constant for a forward reaction, 2 A⇌ B, what is Kc'' for the reaction 4 A⇌ 2B? A) Kc B) Kc C) 2 Kc D) (Kc)2 Answer: D Diff: 2 Topic: Section 13.2 The Equilibrium Constant Kc 7) Write the equilibrium constant expression for the following reaction in the forward direction: 2 CH4 (g) + 3 O2 (g) ⇌ 2 CO (g) + 4 H2O (g) A) Kc = B) Kc = C) Kc = D) Kc = Answer: C Diff: 2 Topic: Section 13.2 The Equilibrium Constant Kc 2 Copyright © 2014 Pearson Education, Inc. 8) Write the equilibrium constant expression for the following reaction in the reverse direction: 2 CH4 (g) + 3 O2 (g) ⇌ 2 CO (g) + 4 H2O (g) A) Kc' = B) Kc' = C) Kc' = D) Kc' = Answer: D Diff: 2 Topic: Section 13.2 The Equilibrium Constant Kc 9) Nitric oxide reacts with oxygen to form nitrogen dioxide: 2 NO(g) + O2(g) ⇌ 2 NO2(g) What is Kc for the forward reaction if the equilibrium concentration of NO is 0.200 M, O2 is 0.100 M, and NO2 is 0.250 M at 25°C? A) 8.00 × 10-2 B) 6.41 × 10-2 C) 12.5 D) 15.6 Answer: D Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc 10) Nitric oxide reacts with oxygen to form nitrogen dioxide: 2 NO(g) + O2(g) ⇌ 2 NO2(g) What is Kc' for the reverse reaction if the equilibrium concentration of NO is 0.300 M, O2 is 0.200 M, and NO2 is 0.530 M at ? A) 0.0340 B) 0.0641 C) 0.624 D) 15.6 Answer: B Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc 3 Copyright © 2014 Pearson Education, Inc. 11) A mixture of carbon monoxide, hydrogen, and methanol is at equilibrium. The balanced chemical equation is: . At 250°C, the mixture contains 0.0960 M CO, 0.191 M H2, and 0.150 M CH3OH. What is the value for Kc? A) 2.33 × 10-2 B) 0.244 C) 4.09 D) 42.8 Answer: D Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc 12) Given the reaction: 2 HI ⇌ H2 + I2. If Kc' for the reverse reaction is 1.85 × 10-2 at 425°C, what is Kc for the forward reaction at the same temperature? A) -1.85 × 10-2 B) 1.85 × 10-2 C) 3.70 × 10-2 D) 54.1 Answer: D Diff: 2 Topic: Section 13.2 The Equilibrium Constant Kc 13) For the reaction: N2(g) + 2 O2(g) ⇌ 2 NO2(g), Kc = 8.3 × 10-10 at 25°C. What is the concentration of N2 gas at equilibrium when the concentration of NO2 is twice the concentration of O2 gas? A) 2.1 × 10-10 M B) 4.2 × 10-10 M C) 2.4 × 109 M D) 4.8 × 109 M Answer: D Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc Algo. Option: algorithmic 14) If Kc = 7.04 × 10-2 for the reaction: 2 HBr(g) ⇌ H2(g) + Br2(g), what is the value of Kc for the reaction: ? A) 3.52 × 10-2 B) 0.265 C) 3.77 D) 28.4 Answer: C Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc 4 Copyright © 2014 Pearson Education, Inc. 15) If Kc equals 0.11 at 25°C for the reaction: N2O4(g) ⇌ 2 NO2(g), what is Kc for the reaction: NO2(g) ⇌ 1/2 N2O4(g)? A) 0.33 B) 3.0 C) 4.5 D) 9.1 Answer: B Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc 16) Which one of the following statements about the equilibrium constant, Kp, is false? A) Δn is equal to the sum of the coefficients of the gaseous products minus the sum of the coefficients of the gaseous reactants. B) The relationship between Kp and Kc is: Kp = Kc (RT)Δn C) The units for Kp are usually omitted. D) Total pressures are used in the equilibrium equation in place of molar concentrations. Answer: D Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 17) Write the equilibrium constant expression for the following reaction in the forward direction: 2 CH4(g) + 3 O2(g) ⇌ 2 CO(g) + 4 H2O(g) A) Kp = B) Kp= C) Kp = D) Kp = Answer: B Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 5 Copyright © 2014 Pearson Education, Inc. 18) Write the equilibrium constant expression for the following reaction in the reverse direction: 2 CH4(g) + 3 O2(g) ⇌ 2 CO(g) + 4 H2O(g) A) Kp' = B) Kp' = C) Kp' = D) Kp' = Answer: A Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 19) What is true about the relationship of Kp and Kc for the reaction: 2 CH4(g) + 3 O2(g) ⇌ 2 CO(g) + 4 H2O(g)? A) Kp < Kc B) Kp = Kc C) Kp > Kc D) Kp and Kc are not related. Answer: C Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 20) The oxidation of sulfur dioxide by oxygen to sulfur trioxide has been implicated as an important step in the formation of acid rain: 2 SO2(g) + O2(g) ⇌ 2 SO3(g). If the equilibrium partial pressures of SO2, O2, and SO3 are 0.564 atm, 0.102 atm, and 0.333 atm respectively at 1000 K, what is Kp at that temperature? A) 0.292 B) 3.42 C) 5.79 D) 8.11 Answer: B Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 6 Copyright © 2014 Pearson Education, Inc. 21) Given the reaction at a certain temperature: 2 HI(g) ⇌ H2(g) + I2(g). At equilibrium, the partial pressure of HI is 1.8 × 10-3 atm, and the partial pressures for H2 and I2 are 0.10 atm each. Find Kp at that temperature. A) 3.2 × 10-4 B) 5.6 × 101 C) 3.1 × 103 D) 3.1 × 104 Answer: C Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 22) If Kc = 2.0 x 1033 at 25°C, for the following reaction: H2(g) + Cl2(g) ⇌ 2 HCl(g), then find Kp at the same temperature. A) 8.2 × 1031 B) 9.7 × 1032 C) 2.0 × 1033 D) 4.9 × 1034 Answer: C Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 23) Phosphorus pentachloride decomposes to phosphorus trichloride and chlorine gas at elevated temperatures by the following reaction: PCl5(g) ⇌ PCl3(g) + Cl2(g). If Kc = 1.8 at 250°C, what is the value of Kp at the same temperature? A) 4.2 × 10-2 B) 8.8 × 10-2 C) 65 D) 77 Answer: D Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 24) The decomposition of ammonia is: 2 NH3(g) = N2(g) + 3 H2(g). If Kp is 1.5 × 103 at 400°C, what is the partial pressure of ammonia at equilibrium when N2 is 0.10 atm and H2 is 0.15 atm? A) 2.2 × 10-7 atm B) 4.7 × 10-4 atm C) 2.1 × 103 atm D) 4.4 × 106 atm Answer: B Diff: 3 Topic: Section 13.4 The Equilibrium Constant Kp Algo. Option: algorithmic 7 Copyright © 2014 Pearson Education, Inc. 25) The decomposition of ammonia is: 2 NH3(g) ⇌ N2(g) + 3 H2(g). If the partial pressure of ammonia is 1.6 × 10-3 atm and the partial pressures of N2 and H2 are each 0.25 atm at equilibrium, what is the value for Kc at 400°C for the forward reaction? A) 0.50 B) 1.4 C) 1.5 × 103 D) 4.6 × 106 Answer: A Diff: 4 Topic: Section 13.4 The Equilibrium Constant Kp 26) The decomposition of ammonia is: 2 NH3(g) ⇌ N2(g) + 3 H2(g). If the pressure of ammonia is 1.0 × 10-3 atm, and the pressures of N2 and H2 are each 0.20 atm, what is the value for Kp' at 400°C for the reverse reaction? A) -6.2 × 10-4 B) -1.6 × 103 C) 6.2 × 10-4 D) 1.6 × 103 Answer: C Diff: 3 Topic: Section 13.4 The Equilibrium Constant Kp 27) A 1.50 L vessel contains an equilibrium mixture of 0.100 mol of NO, 0.150 mol of Br2, and 0.250 mol of NOBr at 25°C. What is the value of Kp for the reaction below? 2 NO(g) + Br2(g) ⇌ 2 NOBr(g)? A) 2.56 B) 62.5 C) 1.28 × 102 D) 1.53 × 103 Answer: A Diff: 4 Topic: Section 13.4 The Equilibrium Constant Kp 28) As a rule, which of the following phases are not included in the equilibrium constant expression? I. pure liquids II. pure solids III. aqueous solutions IV. gases A) I, II B) I, IV C) III, IV D) II, III Answer: A Diff: 1 Topic: Section 13.5 Heterogeneous Equilibria 8 Copyright © 2014 Pearson Education, Inc. 29) Which equilibrium below is homogeneous? A) BaSO4(s) ⇌ Ba2+(aq) + SO42-(aq) B) 2 H2O2(l) ⇌ 2 H2O(l) + O2(g) C) NH4NO3(s) ⇌ N2O(g) + 2 H2O(g) D) 2 CO(g) + O2(g) ⇌ 2 CO2(g) Answer: D Diff: 1 Topic: Section 13.5 Heterogeneous Equilibria 30) What is the equilibrium equation for the dissociation of formic acid in water? HCOOH (aq) + H2O (l) ⇌ H3O+ (aq) + HCOO- (aq) A) Kc = B) Kc = C) Kc = D) Kc = Answer: C Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 31) What is the equilibrium equation for the following reaction? C2H4 (g) + 3 O2 (g) ⇌ 2 CO2 (g) + 2 H2O (l) A) Kp = B) Kp = C) Kp = D) Kp = Answer: D Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 9 Copyright © 2014 Pearson Education, Inc. 32) What is the equilibrium equation for the following reaction? FeS(s) + 2 H3O+ (aq) ⇌ Fe2+(aq) + H2S (aq) + 2 H2O (l) A) Kc = B) Kc = C) Kc = D) Kc = Answer: D Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 33) What is the equilibrium equation for the following reaction? 2 H2O (l) ⇌ H3O+ (aq) + OH– (aq) A) Kc = B) Kc = C) Kc = D) Kc = [H3O+] [OH–] Answer: D Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 34) What is the value for Kc for the following reaction: PbCl2(s) ⇌ Pb2+(aq) + 2 Cl-(aq), if PbCl2(s) = 1.50 grams, [Pb2+] = 1.6 × 10-2 M and [Cl-] = 3.2 × 10-2 M at equilibrium? (The molar mass of PbCl2(s) is 278 g/mol and its density is 5.85 g/cm3.) A) 7.6 × 10-7 B) 1.6 × 10-5 C) 6.2 × 104 D) 1.3 × 106 Answer: B Diff: 3 Topic: Section 13.5 Heterogeneous Equilibria 10 Copyright © 2014 Pearson Education, Inc. 35) What is the equilibrium constant, Kc, for the reaction: 2 Hg(l) + O2(g) ⇌ 2 HgO(s) if the amounts of reactants and products at equilibrium are: 1.00 g of HgO(s), 2.00 mL of Hg(l), and 1.60 M O2(g)? (The molar mass and density of HgO(s) is 217 g/mol, and 1.10 g/cm3. The molar mass and density of Hg(l) is 201 g/mol, and 13.6 g/mL.) A) 6.85 × 10-4 B) 4.66 × 10-2 C) 0.625 D) 1.46 × 103 Answer: C Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 36) For which one of the following reactions will Kc = Kp? A) CO(g) + 2 H2(g) ⇌ CH3OH(g) B) ZnO(s) + CO(g) ⇌ Zn(s) + CO2(g) C) 2 O3(g) ⇌ 3 O2(g) D) COCl2(g) ⇌ CO(g) + Cl2(g) Answer: B Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 37) If Kc = 0.900, and Kp = 538 for a hypothetical reaction, which of the equations below could represent the reaction at 25°C? A) A(g) + B(s) ⇌ 3 C(g) B) A(l) + 2 B(g) ⇌ 2 C(g) C) B(g) ⇌ C(l) + D(l) D) A(g) ⇌ 2 C(s) + D(g) Answer: A Diff: 3 Topic: Section 13.5 Heterogeneous Equilibria 38) Given the hypothetical reaction: 2 A(s) + x B(g) ⇌ 3 C(g), Kp = 0.0105 and Kc = 0.45 at 250°C. What is the value of the coefficient x? A) 1 B) 2 C) 3 D) 4 Answer: D Diff: 3 Topic: Section 13.5 Heterogeneous Equilibria 11 Copyright © 2014 Pearson Education, Inc. 39) For the reaction, A(g) + 2 B(g) ⇌ 2 C(g), Kc = 1 × 10-10 at 25°C. Which of the following statements is true? A) Δn = +1 B) The concentration of the products is greater than the concentration of the reactants. C) The reaction is favored in the reverse direction. D) The value of Kp will be larger than the value for Kc. Answer: C Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant 40) Which statement is true for a reaction with Kc equal to 2.43 × 10-12? A) Increasing the temperature will not change the value of Kc. B) There are appreciable concentrations of both reactants and products. C) The reaction proceeds hardly at all towards completion. D) The reaction proceeds nearly all the way to completion. Answer: C Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 41) For the reaction: 4 HCl(g) + O2(g) ⇌ 2 Cl2(g) + 2 H2O(l), the equilibrium constant is 0.063 at 400 K. If the reaction quotient is 0.100, which of the following statements is not correct? A) [HCl] will increase. B) [O2] will increase. C) [Cl2] will decrease. D) [H2O] will increase. Answer: D Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant 42) The equilibrium constant is equal to 5.00 at 1300 K for the reaction: 2 SO2(g) + O2(g) ⇌ 2 SO3(g). If initial concentrations are [SO2] = 1.20 M, [O2] = 0.45 M, and [SO3] = 1.80 M, the system is A) at equilibrium. B) not at equilibrium and will remain in an unequilibrated state. C) not at equilibrium and will shift to the left to achieve an equilibrium state. D) not at equilibrium and will shift to the right to achieve an equilibrium state. Answer: A Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 12 Copyright © 2014 Pearson Education, Inc. 43) The equilibrium constant, Kp, equals 3.40 at 25°C for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 1.00 atm of each gas, in what direction will the system shift to reach equilibrium? A) It will shift left. B) It will shift right. C) The system is already at equilibrium. D) The system is not at equilibrium and will remain in an unequilibrated state. Answer: B Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 44) Cyclohexane (C6H12) undergoes a molecular rearrangement in the presence of AlCl3 to form methylcyclopentane (MCP) according to the equation: C6H12 ⇌ MCP If Kc = 0.143 at 25°C for this reaction, predict the direction the reaction will shift if the initial concentrations of C6H12 and MCP are 0.200 M and 0.100 M, respectively. The system A) will shift left. B) will shift right. C) is already at equilibrium. D) is not at equilibrium and will remain in an unequilibrated state. Answer: A Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 45) At a certain temperature, bromine and nitric oxide react to form nitrosyl bromide: Br2(g) + 2 NO(g) ⇌ 2 NOBr(g). When initial amounts of Br2, NO, and NOBr are mixed, the concentration of NOBr increases. Which statement below is true? A) Kc < Q B) Kc > Q C) Kc = Q D) More information is needed to make a statement about Kc. Answer: B Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 13 Copyright © 2014 Pearson Education, Inc. 46) At a certain temperature, bromine and nitric oxide react to form nitrosyl bromide: Br2(g) + 2 NO(g) ⇌ 2 NOBr(g). When 0.010 mol Br2 is mixed with 0.025 mol NO and 0.015 mol NOBr in a 2.50 L flask, the concentration of NOBr decreases. Which statement below is true? A) Kc < 36 B) Kc > 36 C) Kc < 90 D) Kc > 90 Answer: C Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 47) An equilibrium mixture of CO, O2 and CO2 at a certain temperature contains 0.0010 M CO2 and 0.0015 M O2. At this temperature, Kc, equals 1.4 × 102 for the reaction: 2 CO(g) + O2(g) ⇌ 2 CO2(g). What is the equilibrium concentration of CO? A) 4.8 × 10-6 M B) 2.2 × 10-3 M C) 9.3 × 10-2 M D) 3.1 × 10-1 M Answer: B Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 48) At a certain temperature, Kc equals 1.4 × 102 for the reaction: 2 CO(g) + O2(g) ⇌ 2 CO2(g). If a 2.50-L flask contains 0.400 mol of CO2 and 0.100 mol of O2 at equilibrium, how many moles of CO are also present in the flask? A) 0.422 mol B) 0.169 mol C) 0.107 mol D) 0.0114 mol Answer: B Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 14 Copyright © 2014 Pearson Education, Inc. 49) For the isomerization reaction: butane ⇌ isobutane Kp equals 25 at 500°C. If the initial pressures of butane and isobutane are 10. atm and 0.0 atm, respectively, what are the pressures of the two gases at equilibrium? A) P(butane) = 0.38 atm and P(isobutane) = 9.6 atm B) P(butane) = 0.40 atm and P(isobutane) = 10. atm C) P(butane) = 9.6 atm and P(isobutane) = 0.38 atm D) P(butane) = 10 atm and P(isobutane) = 0.40 atm Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 50) The following two isomers of C3H7NO exist in equilibrium with each other in solution: If Kc = 0.57 at 25°C and the initial concentration of the reactant is 0.50 M and the product is 0.70 M, what are the concentrations at equilibrium? A) [reactant] = 0.43 M and [product] = 0.24 M B) [reactant] = 0.67 M and [product] = 0.38 M C) [reactant] = 0.76 M and [product] = 0.44 M D) [reactant] = 0.82 M and [product] = 0.47 M Answer: C Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 51) Cyclohexane (C6H12) undergoes a molecular rearrangement in the presence of AlCl3 to form methylcyclopentane (CH3C5H9) according to the equation: C6H12 ⇌ CH3C5H9 If Kc = 0.143 at 25°C for this reaction, find the equilibrium concentrations of C6H12 and CH3C5H9 if the initial concentrations are 0.200 M and 0.100 M, respectively. A) [C6H12] = 0.0625 and [CH3C5H9] = 0.062 M B) [C6H12] = 0.138 and [CH3C5H9] = 0.162 M C) [C6H12] = 0.262 M and [CH3C5H9] = 0.038 M D) [C6H12] = 0.282 and [CH3C5H9] = 0.018 M Answer: C Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 15 Copyright © 2014 Pearson Education, Inc. 52) At a certain temperature the equilibrium constant, Kc, equals 0.11 for the reaction: 2 ICl(g) ⇌ I2(g) + Cl2(g). What is the equilibrium concentration of ICl if 0.75 mol of I2 and 0.75 mol of Cl2 are initially mixed in a 2.0-L flask? A) 0.23 M B) 0.28 M C) 0.45 M D) 0.56 Answer: C Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 53) The equilibrium constant, Kp, equals 3.40 for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.125 atm of trans-2-butene, what is the equilibrium pressure of each gas? A) P(cis-2-butene) = 0.037 atm, P(trans-2-butene) = 0.125 atm B) P(cis-2-butene) = 0.048 atm, P(trans-2-butene) = 0.165 atm C) P(cis-2-butene) = 0.074 atm, P(trans-2-butene) = 0.250 atm D) P(cis-2-butene) = 0.085 atm, P(trans-2-butene) = 0.290 atm Answer: D Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 54) Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the reaction: At 250°C, 0.250 M PCl5 is added to a flask. If Kc = 1.80, what are the equilibrium concentrations of each gas? A) [PCl5] = 0.0280 M, [PCl3] = 0.222 M, [Cl2] = 0.222 M B) [PCl5] = 1.25 M, [PCl3] = 0.474 M, [Cl2] = 0.474 M C) [PCl5] = 1.80 M, [PCl3] = 1.80 M, [Cl2] = 1.80 M D) [PCl5] = 2.27 M, [PCl3] = 2.02 M, [Cl2] = 2.02 M Answer: A Diff: 5 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 16 Copyright © 2014 Pearson Education, Inc. 55) The esterification of acetic acid and ethanol is given by the reaction below: C2H5OH(aq) + CH3COOH(aq) ⇌ CH3COOC2H5(aq) + H2O(l) When 1.00 mol of ethanol was mixed with 2.00 mol of acid in a 1.00 L flask, 0.86 mol of ester was formed at room temperature. What is the value of the equilibrium constant, Kc? A) 0.43 B) 2.3 C) 4.6 D) 5.4 Answer: D Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant 56) Kp is equal to 48.70 at 731 K for the reaction: H2(g) + I2(g) ⇌ 2 HI(g). Initially the mixture contains 0.08592 atm each of H2 and I2 and 1.0000 atm of HI. What is the pressure of HI at equilibrium? A) 0.7955 atm B) 0.9108 atm C) 0.9140 atm D) 0.9498 atm Answer: B Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant 57) When baking soda is heated it decomposes according to the following reaction: 2 NaHCO3(s) ⇌ Na2CO3(s) + H2O(g) + CO2(g) If sufficient baking soda is placed in a container and heated to 90°C, the total pressure of the gases is 0.5451 atm. What is the value of Kp at that temperature? A) 0.07428 B) 0.2973 C) 0.4228 D) 1.091 Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 17 Copyright © 2014 Pearson Education, Inc. 58) Ammonium carbamate can dissociate into gases at 25°C according to the reaction: NH2COONH4(s) ⇌ 2 NH3(g) + CO2(g) If sufficient ammonium carbamate is sealed in a flask, the total pressure will be 0.117 atm at equilibrium. What is the value of Kp at 25°C? A) 2.37 × 10-4 B) 2.00 × 10-4 C) 1.60 × 10-3 D) 3.42 × 10-1 Answer: A Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant 59) Gaseous hydrogen bromide decomposes at elevated temperatures according to the following equation: . At a certain temperature a 2.00 L flask is initially filled only with 0.600 mol of HBr. What is the value of Kc at that temperature if the flask contains 0.104 mol of H2 at equilibrium? A) 7.04 × 10-2 B) 4.40 × 10-2 C) 3.00 × 10-2 D) 2.10 × 10-1 Answer: A Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant 60) When reaction (1) and (2) below are added together, the result is reaction (3). 1) H2O(l) + HNO2(aq) ⇌ H3O+(aq) + NO2-(aq) 2) H3O+(aq) + OH-(aq) ⇌ 2 H2O(l) 3) HNO2(aq) + OH-(aq) ⇌ NO2-(aq) + H2O(l) If K1 = 4.50 × 10-4, and K2 = 1.00 × 1014, find the equilibrium constant, K3. A) 4.50 × 10-18 B) 4.50 × 1010 C) 1.00 × 1014 D) 2.22 × 1017 Answer: B Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 18 Copyright © 2014 Pearson Education, Inc. 61) Oxalic acid can donate two protons to water in successive reactions: (1) H2C2O4(aq) + H2O(l) ⇌ H3O+(aq) + HC2O4-(aq) (2) HC2O4-(aq) + H2O(l) ⇌ H3O+(aq) + C2O42-(aq) If Kc1 = 5.9 × 10-2 and Kc2 = 6.4 × 10-5 at 25°C, what is the value of Kc for reaction (3)? (3) H2C2O4(aq) + 2 H2O(l) ⇌ 2 H3O+(aq) + C2O42-(aq) A) 3.8 × 10-6 B) 1.1 × 10-3 C) 5.9 × 10-2 D) 9.2 × 102 Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 62) Acids donate protons to water according to the general equation: HA(aq) + H2O(l) ⇌ H3O+(aq) + A-(aq) Consider the following acids and their equilibrium constants for reaction with water at 25°C. If all the acids have the same initial concentration, which is the strongest acid (i.e. which donates the most protons to water)? A) HBrO, Kc = 2.0 × 10-9 B) HNO2, Kc = 4.5 × 10-4 C) HF, Kc = 3.5 × 10-4 D) HIO3, Kc = 1.7 × 10-1 Answer: D Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant 63) For acid solutions of the same molarity acid strength is proportional to the equilibrium concentration of H3O+. For equimolar solutions of acids, which equilibrium expression below corresponds to the strongest acid? A) Kc = = 3.5 × 10–4 B) Kc = = 3.5 × 10–8 C) Kc = = 4.5 × 10–4 D) Kc = = 4.9 × 10–10 Answer: C Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant 19 Copyright © 2014 Pearson Education, Inc. 64) The equilibrium constant Kc for the reaction HF(aq) + H2O(l) ⇌ H3O+(aq) +F-(aq) is 3.5 × 10-4. What is the equilibrium concentration of H3O+ if the initial concentration of HF is 1.0 M? A) 1.0 M B) 3.5 × 10–2 M C) 1.9 × 10–2 M D) 1.9 × 10-4 M Answer: C Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant 65) The solubility of 1:1 salts is measured by the equilibrium constant for the general reaction: MX(s) = Mn+(aq) + Xn-(aq). Given the following salts and their equilibrium constants for the reaction above at 25°C, which salt is the least soluble? A) MgCO3, Kc = 6.8 × 10-6 B) CaCO3, Kc = 5.0 × 10-9 C) SrCO3, Kc = 5.6 × 10-10 D) BaCO3, Kc = 2.6 × 10-9 Answer: C Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 66) Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the general reaction: MaXb(s) ⇌ a Mb+(aq) + b Xa-(aq). Given the following salts and their equilibrium constants for the reaction above at 25°C, which salt is the least soluble? A) AgCl, Kc = 1.8 × 10-10 B) Ag2SO4, Kc = 1.2 × 10-5 C) CaCO3, Kc = 2.6 × 10-9 D) CaF2, Kc = 1.5 × 10–10 Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 67) "If a stress is applied to a reaction mixture at equilibrium, the reaction occurs in the direction that will relieve the stress." This statement is called A) the First Law of Thermodynamics. B) the Law of Combining Volumes. C) the Law of Mass Action. D) Le Châtelier's principle. Answer: D Diff: 2 Topic: Section 13.7 Factors That Alter the Composition of an Equilibrium Mixture: Le Châtelier' Principle 20 Copyright © 2014 Pearson Education, Inc. 68) Which of the following changes in reaction conditions will alter the composition of an equilibrium mixture of gases for a reaction having unequal moles of gaseous products and gaseous reactants? A) addition of reactants or products B) decreasing the pressure or volume C) increasing the temperature D) All of the above will alter the equilibrium concentrations. Answer: D Diff: 2 Topic: Section 13.7 Factors That Alter the Composition of an Equilibrium Mixture: Le Châtelier' Principle 69) For a homogeneous equilibrium of gases, which of the following changes in reaction conditions will not alter the equilibrium concentrations? A) addition of an inert gas to the reaction mixture B) addition of reactants or products C) decreasing the pressure or volume D) increasing the temperature Answer: A Diff: 2 Topic: Section 13.7 Factors That Alter the Composition of an Equilibrium Mixture: Le Châtelier' Principle 70) For the reaction shown below, which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H2(g) ⇌ CH4(g) ΔH° = – 74.8 kJ A) adding more C B) decreasing the concentration of H2 C) increasing the concentration of H2 D) increasing the concentration of CH4 Answer: C Diff: 3 Topic: Section 13.8 The Effect of Concentration Changes on an Equilibrium Mixture 71) The pink and blue species below form a violet colored mixture at equilibrium: [Co(H2O)6]2+ (aq) + 4 Cl- (aq) ⇌ [CoCl4]2- (aq) + 6 H2O (l) (pink) (blue) 2+ If the concentration of [Co(H2O)6] is increased, what happens to the solution? A) The concentration of [CoCl4]2- increases. B) The concentration of [CoCl4]2- decreases. C) The solution becomes colorless. D) No color change is observed. Answer: A Diff: 3 Topic: Section 13.8 The Effect of Concentration Changes on an Equilibrium Mixture 21 Copyright © 2014 Pearson Education, Inc. 72) Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: Which of the following changes in condition will cause the equilibrium to shift to the right? A) add FeO B) add CO C) add CO2 D) raise the temperature Answer: B Diff: 3 Topic: Section 13.8 The Effect of Concentration Changes on an Equilibrium Mixture 73) The enthalpy for the following reaction is 136 kJ. If the reaction takes place in a closed container, which one of the following reaction conditions will not decrease the concentration of water vapor? 2 NaHCO3(s) ⇌ Na2CO3(s) + CO2(g) + H2O(g) A) add CO2 B) cool the container C) decrease the volume of the container D) remove some NaHCO3 Answer: D Diff: 3 Topic: Section 13.8 The Effect of Concentration Changes on an Equilibrium Mixture 74) A crude type of disappearing ink is based on the following endothermic equilibrium: [Co(H2O)6]Cl2 (aq) ⇌ [CoCl2(H2O)4] (aq) + 2 H2O (l) (colorless) (blue) If the reactant solution is used to on a piece of paper and the paper is allowed to partially dry, what can be done to bring out the colored handwriting? A) add water B) decrease the volume C) put the paper in a freezer D) put the paper in an oven Answer: D Diff: 3 Topic: Section 13.10 The Effect of Temperature Changes on an Equilibrium Mixture 75) For the reaction shown below, which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H2(g) ⇌ CH4(g) ΔH° = – 74.8 kJ A) adding He B) adding more C C) decreasing the volume D) increasing the volume Answer: C Diff: 3 Topic: Section 13.9 The Effect of Pressure and Volume Changes on an Equilibrium Mixture 22 Copyright © 2014 Pearson Education, Inc. 76) Which change in the system will drive equilibrium to the left in the reaction below? N2O5(g) ⇌ NO2(g) + NO3(g) A) decrease the amount of NO3 B) increase the amount of N2O5 C) increase the pressure D) increase the volume Answer: C Diff: 3 Topic: Section 13.9 The Effect of Pressure and Volume Changes on an Equilibrium Mixture 77) Ammonium bromide is a crystalline solid that decomposes endothermically when heated: NH4Br(s) ⇌ NH3(g) + HBr(g). When solid NH4Br is added to an evacuated flask at 300°C, which change in reaction conditions below will cause the equilibrium to shift to the right? A) add more NH3 B) add more NH4Br C) decrease the temperature D) double the volume of the container Answer: D Diff: 3 Topic: Section 13.9 The Effect of Pressure and Volume Changes on an Equilibrium Mixture 78) For the reaction shown below, which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H2(g) ⇌ CH4(g) ΔH° = – 74.8 kJ A) adding more C B) increasing the volume C) lowering the temperature D) raising the temperature Answer: C Diff: 3 Topic: Section 13.10 The Effect of Temperature Changes on an Equilibrium Mixture 79) The overall reaction for photosynthesis can be represented by the following equation: 6 CO2(g) + 6 H2O(l) ⇌ C6H12O6(s) + 6 O2(g) The enthalpy change for this reaction is 2802 kJ. Which of the following changes in condition will shift the equilibrium to the right? A) increase the pressure of O2 B) increase the temperature C) remove CO2 by reaction with CaO(s) D) remove one-half of C6H12O6(s) Answer: B Diff: 3 Topic: Section 13.10 The Effect of Temperature Changes on an Equilibrium Mixture 23 Copyright © 2014 Pearson Education, Inc. 80) The dissolution of calcium hydroxide is exothermic. Ca(OH)2(s) ⇌ Ca2+(aq) + 2 OH-(aq) What happens when the solution of Ca(OH)2 is heated? A) The amount of Ca(OH)2(s) decreases. B) The amount of Ca(OH)2(s) increases. C) The amount of Ca(OH)2(s) remains unchanged. D) The Ca(OH)2(s) completely dissolves. Answer: B Diff: 2 Topic: Section 13.10 The Effect of Temperature Changes on an Equilibrium Mixture 81) Calcium carbonate is relatively insoluble and the dissolution reaction is endothermic: CaCO3(s) ⇌ Ca2+(aq) + CO32-(aq). Which change in reaction condition below will shift the equilibrium to the right? A) add an acid to react with CO32- ion B) add an anion with which Ca2+ is even less soluble than calcium carbonate C) increase the temperature D) All of the above will shift reaction to the right. Answer: D Diff: 3 Topic: Section 13.10 The Effect of Temperature Changes on an Equilibrium Mixture 82) The decomposition of nitrosyl bromide is exothermic: 2 NOBr(g) ⇌ 2 NO(g) + Br2(g). Which of the following changes in reaction condition will shift the reaction to the left? A) add more NOBr B) decrease the temperature C) increase the container volume D) none of the above Answer: D Diff: 3 Topic: Section 13.10 The Effect of Temperature Changes on an Equilibrium Mixture 83) Which of the following changes in reaction conditions will not alter the composition of a homogeneous equilibrium mixture of gases in a reaction having unequal moles of gaseous products and reactants? A) addition of a catalyst B) addition of reactants or products C) decreasing the temperature D) increasing the pressure or volume Answer: A Diff: 2 Topic: Section 13.11 The Effect of a Catalyst on Equilibrium 24 Copyright © 2014 Pearson Education, Inc. 84) Which of the following statements about a catalyst is true? A) A catalyst changes the position of the equilibrium in a reaction. B) A catalyst increases the temperature of a reaction. C) A catalyst is consumed in a chemical reaction. D) A catalyst provides a lower energy pathway for a reaction. Answer: D Diff: 2 Topic: Section 13.11 The Effect of a Catalyst on Equilibrium 85) A catalyst increases the overall rate of reaction by lowering the activation energy, Ea, for A) both the forward reaction and the reverse reaction. B) neither the forward reaction nor the reverse reaction. C) only the forward reaction. D) only the reverse reaction. Answer: A Diff: 2 Topic: Section 13.11 The Effect of a Catalyst on Equilibrium 86) A catalyst increases the rate of a chemical reaction by providing a lower-energy mechanism for the reaction. When this occurs, which one of the following is not affected? A) activation energy for the forward reaction B) activation energy for the reverse reaction C) equilibrium constant D) rate of the reverse reaction Answer: C Diff: 2 Topic: Section 13.11 The Effect of a Catalyst on Equilibrium 87) A reaction reaches dynamic equilibrium at a given temperature when A) the amount of products exceeds the amount of reactants. B) kfwd equals krev. C) opposing reactions cease and the system is static. D) the relative amounts of reactants and products are constant and ratefwd = raterev. Answer: D Diff: 2 Topic: Section 13.3 The Link Between Chemical Equilibrium and Chemical Kinetics 25 Copyright © 2014 Pearson Education, Inc. 88) Find the equilibrium constant for the reaction: at 25°C when k equals for the reaction at 25°C and k equals for the reaction: A) 3.8 × 10-25 B) 1.7 × 10-12 C) 1.1 × 10-12 D) 5.2 Answer: D Diff: 3 Topic: Section 13.3 The Link Between Chemical Equilibrium and Chemical Kinetics 89) At 25°C, a certain first order reaction has a rate constant equal to 1.00 × 10-3 s-1 and an equilibrium constant, Kc, equal to 4.18. What is the rate constant for the reverse reaction? A) 2.39 × 10-4 s-1 B) 34.18 × 10-3 s-1 C) 2.39 × 102 s-1 D) 4.18 × 103 s-1 Answer: A Diff: 3 Topic: Section 13.3 The Link Between Chemical Equilibrium and Chemical Kinetics 90) Nickel metal can be prepared by the reduction of nickel oxide: NiO(s) + CO(g) ⇌ CO2(g) + Ni(s) At 936 K, Kp = 4.54 × 103 and at 1125 K, Kp = 1.58 × 103. Which statement is true? A) The activation energy decreases with increasing temperature. B) The activation energy increases with increasing temperature. C) The reaction is endothermic. D) The reaction is exothermic. Answer: D Diff: 2 Topic: Section 13.4 The Equilibrium Constant Kp 26 Copyright © 2014 Pearson Education, Inc. 91) The hexaammine cobalt(III) ion is very unstable in acidic aqueous solution: [Co(NH3)6]3+(aq) + 6 H3O+(aq) → [Co(H2O)6]4+(aq) + 6 NH4+(aq) However, solutions of hexaammine cobalt(III) can be stored in acidic solution for months without noticeable decomposition. Which statement below about the equilibrium constant and the activation energy for the reaction is true? A) Keq < 103 and Ea is very small. B) Keq > 103 and Ea is very small. C) Keq < 103 and Ea is very large. D) Keq > 103 and Ea is very large. Answer: D Diff: 4 Topic: Section 13.3 The Link Between Chemical Equilibrium and Chemical Kinetics 92) The reaction below virtually goes to completion because cyanide ion forms very stable complexes with Ni2+ ion: [Ni(H2O)6]2+(aq) + 4 CN-(aq) → [Ni(CN)4]2-(aq) + 6 H2O(l) At the same time, incorporation of 14C labelled cyanide ion (14CN-) is very rapid: [Ni(CN)4]2-(aq) + 4 14CN-(aq) = [Ni(14CN)4]2-(aq) + 4 CN-(aq) Which statement below is correct with regard to stability and rate of reaction? A) Equilibrium is static. B) Stable species can react rapidly. C) Stable species do not react rapidly. D) Unstable species react rapidly. Answer: B Diff: 3 Topic: Section 13.3 The Link Between Chemical Equilibrium and Chemical Kinetics 27 Copyright © 2014 Pearson Education, Inc. Consider the interconversion of A molecules (shaded spheres) and B molecules (unshaded spheres) according to the reaction A ⇌ B. Each of the following series of pictures represents a separate experiment in which time increases from left to right. 93) Which of these experiments has resulted in an equilibrium state? A) all of the experiments except experiment (1) B) all of the experiments except experiment (2) C) all of the experiments except experiment (3) D) all of the experiments except experiment (4) Answer: B Diff: 2 Topic: Conceptual Problems 94) What is the value of the equilibrium constant Kc for the reaction A ⇌ B? A) Kc = 0.33 B) Kc = 3.0 C) Kc = 12 D) 2Kc = 27 Answer: B Diff: 3 Topic: Conceptual Problems 28 Copyright © 2014 Pearson Education, Inc. The following pictures represent the equilibrium state for four different reactions of the type A atoms are unshaded. X atoms are shaded. 95) Which reaction has the largest equilibrium constant? A) A2 + B2 ⇌ 2 AB B) A2 + C2 ⇌ 2 AC C) A2 + D2 ⇌ 2 AD D) A2 + E2 ⇌ 2 AE Answer: A Diff: 3 Topic: Conceptual Problems 96) Which reaction has the smallest equilibrium constant? A) A2 + B2 ⇌ 2 AB B) A2 + C2 ⇌ 2 AC C) A2 + D2 ⇌ 2 AD D) A2 + E2 ⇌ 2 AE Answer: C Diff: 3 Topic: Conceptual Problems 97) The reaction A2 + B2 ⇌ 2 AB has an equilibrium constant Kc = 1.8. The following pictures represent reaction mixtures that contain A2 molecules (shaded) and B2 molecules (unshaded), and AB molecules. Which reaction mixture is at equilibrium? A) reaction mixture (1) B) reaction mixture (2) C) reaction mixture (3) D) reaction mixture (4) Answer: B Diff: 3 Topic: Conceptual Problems 29 Copyright © 2014 Pearson Education, Inc. 98) The following pictures represent mixtures of cis-C2H2X2 molecules and trans-C2H2X2 molecules, which interconvert according to the equation cis-C2H2X2 ⇌ trans-C2H2X2. If mixture (1) is at equilibrium, which of the other mixtures are also at equilibrium? A) mixture (2) B) mixture (3) C) mixture (4) D) None of the other mixtures are at equilibrium. Answer: B Diff: 3 Topic: Conceptual Problems 99) The following pictures represent mixtures of cis-C2H2X2 molecules and trans-C2H2X2 molecules, which interconvert according to the equation cis-C2H2X2 ⇌ trans-C2H2X2. If mixture (1) is at equilibrium, which of the other mixtures are also at equilibrium? A) mixture (2) B) mixture (3) C) mixture (4) D) None of the other mixtures are at equilibrium. Answer: D Diff: 3 Topic: Conceptual Problems 30 Copyright © 2014 Pearson Education, Inc. 100) The following pictures represent mixtures of A2B4 molecules and AB2 molecules, which interconvert according to the equation A2B4 ⇌ 2 AB2. If mixture (1) is at equilibrium, which of the other mixtures are also at equilibrium? A) mixture (2) B) mixture (3) C) mixture (4) D) None of the other mixtures are at equilibrium. Answer: A Diff: 3 Topic: Conceptual Problems 101) The following pictures represent mixtures of A2B4 molecules and AB2 molecules, which interconvert according to the equation A2B4 ⇌ 2 AB2. If mixture (1) is at equilibrium, which of the other mixtures are also at equilibrium? A) mixture (2) B) mixture (3) C) mixture (4) D) None of the other mixtures are at equilibrium. Answer: C Diff: 3 Topic: Conceptual Problems 31 Copyright © 2014 Pearson Education, Inc. 102) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of the equilibrium constant is A) Kc < 1. B) Kc = 0. C) Kc = 1. D) Kc > 1. Answer: D Diff: 2 Topic: Conceptual Problems 103) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of the equilibrium constant is A) Kc < 1. B) Kc = 0. C) Kc = 1. D) Kc > 1. Answer: A Diff: 2 Topic: Conceptual Problems 32 Copyright © 2014 Pearson Education, Inc. 104) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of the equilibrium constant is A) Kc < 1. B) Kc = 0. C) Kc = 1. D) Kc > 1. Answer: C Diff: 2 Topic: Conceptual Problems 105) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of the equilibrium constant is A) Kc < 1. B) Kc = 0. C) Kc = 1. D) Kc > 1. Answer: A Diff: 2 Topic: Conceptual Problems 33 Copyright © 2014 Pearson Education, Inc. 106) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of the equilibrium constant is A) Kc < 1. B) Kc = 0. C) Kc = 1. D) Kc > 1. Answer: A Diff: 2 Topic: Conceptual Problems 107) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of the equilibrium constant is A) Kc < 1. B) Kc = 0. C) Kc = 1. D) Kc > 1. Answer: A Diff: 2 Topic: Conceptual Problems 34 Copyright © 2014 Pearson Education, Inc. 108) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse reaction kr? A) kf < kr B) kf = kr = 0 C) kf = kr D) kf > kr Answer: C Diff: 2 Topic: Conceptual Problems 109) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse reaction kr? A) kf < kr B) kf = kr = 0 C) kf = kr D) kf > kr Answer: D Diff: 2 Topic: Conceptual Problems 35 Copyright © 2014 Pearson Education, Inc. 110) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse reaction kr? A) kf < kr B) kf = kr = 0 C) kf = kr D) kf > kr Answer: A Diff: 2 Topic: Conceptual Problems The reaction A2 + B2 ⇌ 2AB has an equilibrium constant Kc = 1.8. The following pictures represent reaction mixtures that contain A2 molecules (shaded) and B2 molecules (unshaded), and AB molecules. 111) Which nonequilibrium mixture will react in the forward direction to reach equilibrium? A) reaction mixture (1) B) reaction mixture (2) C) reaction mixture (3) D) reaction mixture (4) Answer: C Diff: 3 Topic: Conceptual Problems 112) Which nonequilibrium mixtures will react in the reverse direction to reach equilibrium? A) reaction mixtures (1) and (2) B) reaction mixtures (1) and (4) C) reaction mixtures (2) and (3) D) reaction mixtures (3) and (4) Answer: B Diff: 3 Topic: Conceptual Problems 36 Copyright © 2014 Pearson Education, Inc. The following pictures represent the initial state and the equilibrium state for the gaseous state reaction of A2 molecules (shaded spheres) with B atoms (unshaded spheres) to give AB molecules. 113) What is the best balanced chemical equation for the reaction? A) A2 + B ⇌ A2B B) 1A2 + 2 B ⇌ A2B2 C) A2 + 2 B ⇌ 2 AB D) 6 A2 + 9 B ⇌ 3 A2 + 3B + 6 AB Answer: C Diff: 1 Topic: Conceptual Problems 114) If the volume of the equilibrium mixture is decreased, what will happen to the number of AB molecules and the number of B atoms? A) The number of AB molecules and the number of B atoms will both decrease. B) The number of AB molecules will increase; the number of B atoms will decrease. C) The number of AB molecules will decrease; the number of B atoms will increase. D) The number of AB molecules and the number of B atoms will both increase. Answer: B Diff: 3 Topic: Conceptual Problems 37 Copyright © 2014 Pearson Education, Inc. Consider the reaction A + B ⇌ 2 AB. The vessel on the right contains an equilibrium mixture of A atoms (shaded spheres), B atoms (unshaded spheres), and AB molecules. 115) If the barrier between the two vessels is removed and the contents of the two vessels are allowed to mix, what will be observed? A) The reaction will go in the forward direction decreasing the number of A atoms and B atoms and increasing the number of AB molecules. B) The reaction will go in the forward direction increasing the number of A atoms and B atoms and decreasing the number of AB molecules. C) The reaction will go in the reverse direction decreasing the number of A atoms and B atoms and increasing the number of AB molecules. D) The reaction will go in the reverse direction increasing the number of A atoms and B atoms and decreasing the number of AB molecules. Answer: D Diff: 3 Topic: Conceptual Problems 38 Copyright © 2014 Pearson Education, Inc. Picture (1) represents the equilibrium mixture for the reaction A + B ⇌ 2 AB at 298 K. 116) If this reaction is exothermic, which picture (2)-(4) represents the equilibrium mixture at 400 K? A) picture (2) B) picture (3) C) picture (4) D) none of the above Answer: C Diff: 3 Topic: Conceptual Problems 117) If this reaction is endothermic, which picture (2)-(4) represents the equilibrium mixture at 400 K? A) picture (2) B) picture (3) C) picture (4) D) none of the above Answer: B Diff: 3 Topic: Conceptual Problems 39 Copyright © 2014 Pearson Education, Inc. 118) Picture (1) represents the equilibrium mixture for the gas-phase reaction A + B ⇌ 2 AB at 298 K. If the volume of the equilibrium mixture is decreased, which picture (2)-(4) represents the equilibrium at the reduced volume? A) picture (2) B) picture (3) C) picture (4) D) none of the above Answer: A Diff: 3 Topic: Conceptual Problems Picture (1) represents an equilibrium mixture of solid CaCO3, solid CaO, and gaseous CO2, obtained as a result of the endothermic decomposition of CaCO3. 119) Which picture (2)-(4) represents the equilibrium mixture after addition of four more CO2 molecules? A) picture (2) B) picture (3) C) picture (4) D) none of the above Answer: A Diff: 3 Topic: Conceptual Problems 120) Which picture (2)-(4) represents the equilibrium mixture at a higher temperature? A) picture (2) B) picture (3) C) picture (4) D) none of the above Answer: C Diff: 3 Topic: Conceptual Problems 40 Copyright © 2014 Pearson Education, Inc. 121) Which picture (2)-(4) represents the equilibrium mixture when a catalyst is added? A) picture (2) B) picture (3) C) picture (4) D) all of the above Answer: A Diff: 2 Topic: Conceptual Problems 122) Which picture (2)-(4) represents the equilibrium mixture when more solid CaCO3 is added? A) picture (2) B) picture (3) C) picture (4) D) all of the above Answer: A Diff: 3 Topic: Conceptual Problems 123) Which picture (2)-(4) represents the equilibrium mixture when more solid CaO is added? A) picture (2) B) picture (3) C) picture (4) D) all of the above Answer: A Diff: 3 Topic: Conceptual Problems 41 Copyright © 2014 Pearson Education, Inc. 13.2 Algorithmic Questions 1) For the reaction: N2(g) + 2 O2(g) ⇌ 2 NO2(g), Kc = 8.3 × 10-10 at 25°C. What is the concentration of N2 gas at equilibrium when the concentration of NO2 is five times the concentration of O2 gas? A) 3.3 × 10-11 M B) 1.7 × 10-10 M C) 6.0 × 109 M D) 3.0 × 1010 M Answer: D Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc Algo. Option: algorithmic 2) The decomposition of ammonia is: 2 NH3(g) = N2(g) + 3 H2(g). If Kp is 1.5 × 103 at 400°C, what is the partial pressure of ammonia at equilibrium when N2 is 0.10 atm and H2 is 0.15 atm? A) 2.2 × 10-7 atm B) 4.7 × 10-4 atm C) 2.1 × 103 atm D) 4.4 × 106 atm Answer: B Diff: 3 Topic: Section 13.4 The Equilibrium Constant Kp Algo. Option: algorithmic 3) The equilibrium constant is equal to 5.00 at 1300 K for the reaction: 2 SO2(g) + O2(g) ⇌ 2 SO3(g). If initial concentrations are [SO2] = 6.00 M, [O2] = 0.45 M, and [SO3] = 9.00 M, the system is A) at equilibrium. B) not at equilibrium and will remain in an unequilibrated state. C) not at equilibrium and will shift to the left to achieve an equilibrium state. D) not at equilibrium and will shift to the right to achieve an equilibrium state. Answer: A Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 42 Copyright © 2014 Pearson Education, Inc. 4) The equilibrium constant, Kp, equals 3.40 at 25°C for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 5.00 atm of each gas, in what direction will the system shift to reach equilibrium? A) It will shift left. B) It will shift right. C) The system is already at equilibrium. D) The system is not at equilibrium and will remain in an unequilibrated state. Answer: B Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 5) Cyclohexane (C6H12) undergoes a molecular rearrangement in the presence of AlCl3 to form methylcyclopentane (MCP) according to the equation: C6H12 ⇌ MCP If Kc = 0.143 at 25°C for this reaction, predict the direction in which the system will shift if the initial concentrations of C6H12 and MCP are 0.0400 M and 0.0200 M, respectively. The system A) will shift left. B) will shift right. C) is already at equilibrium. D) is not at equilibrium and will remain in an unequilibrated state. Answer: A Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 6) At a certain temperature, nitrogen and hydrogen react to form ammonia: N2(g) + 3 H2(g) ⇌ 2 NH3(g). When initial amounts of N2, H2, and NH3 are mixed, the concentration of NH3 increases. Which statement below is true? A) Kc < Q B) Kc > Q C) Kc = Q D) More information is needed to make a statement about Kc. Answer: B Diff: 2 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 43 Copyright © 2014 Pearson Education, Inc. 7) An equilibrium mixture of CO, O2 and CO2 at a certain temperature contains 0.0010 M CO2 and 0.0100 M O2. At this temperature, Kc equals 1.4 × 102 for the reaction: 2 CO(g) + O2(g) ⇌ 2 CO2(g). What is the equilibrium concentration of CO? A) 7.1 × 10-7 M B) 8.4 × 10-4 M C) 1.4 × 10-2 M D) 1.2 × 10-1 M Answer: B Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 8) The equilibrium constant, , is equal to 2.00 at 1000° C for the reaction: 2CO (g) ⇌ C (g) + C (g) If 0.079moles of C and 0.079 moles of C are introduced into a 1.0-L flask, what will be the concentration of CO when equilibrium is reached? A) 0.041 M B) 0.058 M C) 0.021 M D) 0.025 M Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 9) The equilibrium constant, , is equal to 2.00 at 1000° C for the reaction: 2CO (g) ⇌ C (g) + C (g) If 2.0 moles of CO is introduced into in a 1.0-L flask, what will be the concentration of C when equilibrium is reached? A) 0.74 M B) 0.52 M C) 1.01 M D) 0.78 M Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 44 Copyright © 2014 Pearson Education, Inc. 10) The equilibrium constant, , is equal to 1.4 at 1200° K for the reaction: C (g) + (g) ⇌ CO(g) + O(g) If 0.75 moles of C and 0.75 moles of are introduced into a 1.0-L flask, what will be the concentration of C when equilibrium is reached? A) 0.34 M B) 0.41 M C) 0.44 M D) 0.51M Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 11) The equilibrium constant, , is equal to 1.4 at 1200° K for the reaction: C (g) + (g) ⇌ CO(g) + O(g) If 0.65 moles of C and 0.65 moles of are introduced into a 1.0-L flask, what will be the concentration of CO when equilibrium is reached? A) 0.30 M B) 0.35 M C) 0.38 M D) 0.42M Answer: B Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 12) The equilibrium constant, , is equal to 1.4 at 1200° K for the reaction: C (g) + (g) ⇌ CO(g) + O(g) If 0.50 moles of C and 0.60 moles of are introduced into a 1.0-L flask, what will be the concentration of C when equilibrium is reached? A) 0.30 M B) 0.21 M C) 0.35 M D) 0.55M Answer: B Diff: 5 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 45 Copyright © 2014 Pearson Education, Inc. 13) The equilibrium constant, , is equal to 1.4 at 1200° K for the reaction: C (g) + (g) ⇌ CO(g) + O(g) If 0.50 moles of C and 0.60 moles of are introduced into a 1.0-L flask, what will be the concentration of CO when equilibrium is reached? A) 0.30 M B) 0.21 M C) 0.35 M D) 0.55M Answer: A Diff: 5 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 14) At a certain temperature, Kc equals 1.4 × 102 for the reaction: 2 CO(g) + O2(g) ⇌ 2 CO2(g). If a 3.00-L flask contains 0.400 mol of CO2 and 0.100 mol of O2 at equilibrium, how many moles of CO are also present in the flask? A) 0.555 mol B) 0.185 mol C) 0.107 mol D) 0.0114 mol Answer: B Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 15) For the isomerization reaction: butane ⇌ isobutane Kp equals 25 at 500°C. If the initial pressures of butane and isobutane are 20. atm and 0.0 atm, respectively, what are the pressures of the two gases at equilibrium? A) P(butane) = 0.77 atm and P(isobutane) = 19.2 atm B) P(butane) = 0.80 atm and P(isobutane) = 20. atm C) P(butane) = 19.2 atm and P(isobutane) = 0.77 atm D) P(butane) = 20 atm and P(isobutane) = 0.80 atm Answer: A Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 46 Copyright © 2014 Pearson Education, Inc. 16) Cyclohexane, C6H12, undergoes a molecular rearrangement in the presence of AlCl3 to form methylcyclopentane, CH3C5H9, according to the equation: C6H12 ⇌ CH3C5H9 If Kc = 0.143 at 25°C for this reaction, find the equilibrium concentrations of C6H12 and CH3C5H9 if the initial concentrations are 0.200 M and 0.075 M, respectively. A) [C6H12] = 0.041 M, [CH3C5H9] = 0.041 M B) [C6H12] = 0.159 M, [CH3C5H9] = 0.116 M C) [C6H12] = 0.241 M, [CH3C5H9] = 0.034 M D) [C6H12] = 0.253 M, [CH3C5H9] = 0.022 M Answer: C Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 17) At a certain temperature the equilibrium constant, Kc, equals 0.11 for the reaction: 2 ICl(g) ⇌ I2(g) + Cl2(g). What is the equilibrium concentration of ICl if 0.75 mol of I2 and 0.75 mol of Cl2 are initially mixed in a 2.0-L flask? A) 0.22 M B) 0.28 M C) 0.45 M D) 0.56 M Answer: C Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 18) The equilibrium constant, Kp, equals 3.40 for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.145 atm of trans-2-butene, what is the equilibrium pressure of each gas? A) P(cis-2-butene) = 0.0426 atm and P(trans-2-butene) = 0.145 atm B) P(cis-2-butene) = 0.0471 atm and P(trans-2-butene) = 0.160 atm C) P(cis-2-butene) = 0.0735 atm and P(trans-2-butene) = 0.250 atm D) P(cis-2-butene) = 0.0898 atm and P(trans-2-butene) = 0.305 atm Answer: D Diff: 4 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 47 Copyright © 2014 Pearson Education, Inc. 19) Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the equation: At 250° 0.125 M PCl5 is added to the flask. If Kc = 1.80, what are the equilibrium concentrations of each gas? A) [PCl5] = 0.00765 M, [PCl3] = 0.117 M, and [Cl2] = 0.117 M B) [PCl5] = 0.0625 M, [PCl3] = 0.335 M, and [Cl2] = 0.335 M C) [PCl5] = 1.80 M, [PCl3] = 1.80 M, and [Cl2] = 1.80 M D) [PCl5] = 3.96 M, [PCl3] = 3.83 M, and [Cl2] = 3.83 M Answer: A Diff: 5 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 20) Kc is 1.67 × 1020 at 25°C for the formation of iron(III) oxalate complex ion: Fe3+(aq) + 3 C2O42-(aq) ⇌ [Fe(C2O4)3]3-(aq). If 0.0400 M Fe3+ is initially mixed with 1.00 M oxalate ion, what is the concentration of Fe3+ ion at equilibrium? A) 3.51 × 10-22 M B) 0.0100 M C) 4.18 × 1017 M D) 2.85 × 1021 M Answer: A Diff: 5 Topic: Section 13.6 Using the Equilibrium Constant Algo. Option: algorithmic 13.3 Short Answer Questions 1) A reaction in which reactants form products in the forward reaction and products simultaneously form reactants in the reverse reaction is said to be ________. Answer: reversible Diff: 2 Topic: Section 13.1 The State of Chemical Equilibrium 2) In a reversible reaction, when the rate of the forward reaction equals the rate of the reverse reaction, the reaction is at ________. Answer: equilibrium Diff: 2 Topic: Section 13.1 The State of Chemical Equilibrium 48 Copyright © 2014 Pearson Education, Inc. 3) For the reaction shown below, N2O4 and NO2 have equilibrium concentrations, [N2O4]eq = 2.160 × 10–4 and [NO2]eq = 1.001 × 10–3, respectively. The equilibrium constant, Kc, for this reaction equals ________. N2O4(g) ⇌ 2 NO2(g) Answer: 4.64 × 10–3 Diff: 2 Topic: Section 13.2 The Equilibrium Constant Kc 4) For the reaction shown below the value of Kp is ________ than the value of Kc, because △n = ________. N2O4(g) ⇌ 2 NO2(g) Answer: greater, 1 Diff: 3 Topic: Section 13.4 The Equilibrium Constant Kp 5) For the reaction shown below the equilibrium constant expression for Kc = ________. HF(aq) + H2O(l) ⇌ H3O+(aq) + F–(aq) Answer: Diff: 2 Topic: Section 13.5 Heterogeneous Equilibria 6) Kc = 57.0 at 700 K for the reaction shown below. H2(g) + I2(g) ⇌ 2 HI(g) If [H2(g)] = [I2(g)] = 0.200 M at equilibrium, the molar concentration [HI((g)] = ________ at equilibrium. Answer: 1.51 Diff: 3 Topic: Section 13.2 The Equilibrium Constant Kc 7) Kc = 1.2 × 10–42 at 500 K for the reaction shown below. H2(g) ⇌ 2 H(g) If [H2] = 1 × 10–2 M and [H] = 1.2 × 10–22 M, in order to achieve equilibrium a net reaction must occur from ________ to ________ until Qc = ________. Answer: right, left, Kc Diff: 3 Topic: Section 13.6 Using the Equilibrium Constant 49 Copyright © 2014 Pearson Education, Inc. 8) If additional SCN– is added to the equilibrium system shown below, Le Châtelier's principle predicts a net reaction from ________ to ________, causing the red color to become ________. Fe3+(aq) + SCN–(aq) ⇌ FeSCN2+(aq) yellow colorless red Answer: left, right, darker Diff: 3 Topic: Section 13.8 The Effect of Concentration Changes on an Equilibrium Mixture 9) According to Le Châtelier's principle, if the volume of the vessel containing the equilibrium system shown below is decreased, there will be an increase in the concentration of ________ and a decrease in the concentration of ________. H2(g) ⇌ 2 H(g) Answer: H2, H Diff: 2 Topic: Section 13.9 The Effect of Pressure and Volume Changes on an Equilibrium Mixture 10) The reaction below is heated from 20°C to 90°C, according to Le Châtelier's principle, there will be a net reaction from ________ to ________, and the brown color will become ________. N2O4(g) ⇌ 2 NO2(g) △H°= + 57.2 kJ colorless brown Answer: left, right, darker Diff: 3 Topic: Section 13.10 The Effect of Temperature Changes on an Equilibrium Mixture 50 Copyright © 2014 Pearson Education, Inc.