This Document Contains Chapters 15 to 16 Chapter 15 Chemical Equilibrium True/False Questions 1. Equilibrium involves the ideas of sameness and constancy. Answer: True 2. Living things are in equilibrium with their surroundings. Answer: False 3. The rate of a chemical reaction is the amount of reactant that changes to product in a specific amount of time. Answer: True 4. Collisions between reactant molecules do not always lead to the formation of product molecules. Answer: True 5. Reaction rates generally increase as a reaction proceeds. Answer: False 6. The rate of a reaction increases with increasing concentrations of reactants because you have more collisions occurring in a given time period. Answer: True 7. The rate of a chemical reaction is inversely proportional to the temperature. Answer: False 8. A reversible reaction is one that can be stopped and then restarted as needed. Answer: False 9. Dynamic equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction. Answer: True 10. Dynamic equilibrium is established when the rate of the forward reaction goes to zero. Answer: False 11. When dynamic equilibrium is achieved, the concentrations of reactants is equal to the concentrations of the products. Answer: False 12. When dynamic equilibrium is achieved, the rate of the forward and backward reactions go to zero. Answer: False 13. The Equilibrium Constant, Keq, is a way to quantify the relative concentrations of the reactants and products of a reaction at equilibrium. Answer: True 14. It is not necessary to have a balanced equation before writing an equilibrium constant expression. Answer: False 15. The larger the equilibrium constant, the greater is the concentration of reactants relative to products at equilibrium. Answer: False 16. As long as Keq > 1, all reactants will eventually be consumed and leave us exclusively with product molecules. Answer: False 17. Placing a [ ] around the formula of a chemical means that we are referring to the molar concentration of that chemical. Answer: True 18. A reaction that has Keq = 2.0 × 108 will have high concentrations of products. Answer: True 19. A reaction that has Keq = 2.0 × 10-8will have high concentrations of products. Answer: False 20. For a given chemical equation, the coefficients for each substance become the exponents for each substance in the written equilibrium expression. Answer: True 21. If Keq = 2 for the reaction X ⇌ Y, then the Keq, for Y ⇌ X will be 1/2 (or 0.5). Answer: True 22. The equilibrium expression for the reaction: C(s) + 2H2(g) ⇌ CH4(g) is Keq = [CH4]/[C][H2]2 Answer: False 23. The equilibrium expression for the reaction: 2C(s) + 2H2O(l) ⇌ CH4(g) + CO2(g) is Keq = [CH4][CO2] Answer: True 24. The equilibrium expression for the reaction: 2Mg(s) + O2(g) ⇌ 2MgO(s) is Keq = 1/[O2] Answer: True 25. The equilibrium constant, Keq, for an equilibrium reaction will always be the same (at a given temperature) regardless of what the initial concentrations of reactants and products were. Answer: True 26. Le Chatelier's principle states that a chemical system must have a shift in direction in order to force the system to reach equilibrium. Answer: False 27. Le Chatelier's principle states that when a chemical system at equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance. Answer: True 28. Increasing the amount of carbon in the reaction below will cause the reaction to proceed to the left so that equilibrium will be restored. 2C(s) + 2H2O(l) ⇌ CH4(g) + CO2(g) Answer: False 29. Decreasing the amount of carbon dioxide in the reaction below will cause the reaction to proceed to the right so that equilibrium will be restored. 2C(s) + 2H2O(l) ⇌ CH4(g) + CO2(g) Answer: True 30. If you have a chamber of gases at equilibrium, compressing the gases to half the original volume would have the same effect as doubling the pressure. Answer: True 31. Decreasing the volume of the system below causes the reaction to shift towards the right. 2C(s) + 2H2(g) ⇌ CH4(g) Answer: True 32. Increasing the volume of the system below causes the reaction to shift towards the right. 2C(s) + 2H2(g) ⇌ CH4(g) Answer: False 33. In an exothermic reaction, you can consider the emitted heat as a reactant in this system. Answer: False 34. Adding heat to an endothermic reaction causes the reaction to shift to the right. Answer: True 35. Adding heat to an exothermic reaction will cause the reaction to remain unchanged. Answer: False 36. If the equilibrium constant, Keq, for a reaction increases upon heating, the reaction must have been endothermic. Answer: True 37. If an equilibrium reaction shifts to the right when the system is cooled, this indicates that the reaction is endothermic. Answer: False 38. A compound with a relatively small Ksp value indicates that the compound is only partially soluble. Answer: True 39. A compound with a very large Ksp value is generally considered to be only partially soluble. Answer: False 40. Dissolving the compound PbCl2 into water can be represented as PbCl2(s) ⇌ Pb2+(aq) + 2Cl-(aq) so the equilibrium expression is Ksp = [Pb2+][Cl-]2/[PbCl2] Answer: False 41. Iron(II) carbonate (Ksp = 3.07 × 10-11) is more soluble than calcium fluoride (Ksp = 1.46 × 10-10). Answer: False Multiple Choice Questions 42. A description of life is: A) Living things maintain and control their sameness. B) Living things maintain and control their changelessness. C) Living things maintain and control their equilibrium. D) Living things maintain and control their disequilibrium. E) none of the above Answer: D 43. According to the collision theory of chemical reactions: A) high energy collisions result in few successful reactions as there isn't sufficient time for the products to react. B) low energy collisions result in many successful reactions as there is sufficient time for the reactants to form products. C) high energy collisions lead to the successful formation of products. D) low energy collisions do not occur in the gas phase. E) all of the above Answer: C 44. Which of the following changes will increase the reaction rate? A) an increase in the concentration of the products B) a decrease of the reaction temperature C) allowing more time for the reaction D) an increase in the concentration of reactants E) all of the above Answer: D 45. Which of the following changes will increase reaction rate? 1. An increase in the concentration of reactants 2. An increase in temperature 3. Higher-energy collisions between reacting molecules A) 1 and 2 only B) 1 and 3 only C) 2 and 3 only D) All of 1, 2, and 3 E) Neither 1, 2, or 3 Answer: D 46. Why does the rate of the reaction decrease over time? A) Exothermic reactions lose heat which cools the reaction which decreases reaction rate. B) As the reaction proceeds, the concentration of the products results in fewer collisions. C) As the reaction proceeds, a decrease in the concentration of reactants results in fewer successful collisions. D) Not all molecules will react and some choose to stay in their present form. E) none of the above Answer: C 47. Which of the following is TRUE for a system that is in dynamic equilibrium? A) The forward reaction goes to 100% completion. B) The reaction rate of the forward reaction approaches zero. C) The concentration of products is equal to the concentration of the reactants. D) Both the forward and reverse reactions come to a halt. E) none of the above Answer: E 48. Which of the following is TRUE about a chemical system in equilibrium? A) No reaction takes place. B) Temperature changes have no effect on reaction rate. C) Addition of more reactants have no effect on reaction rate. D) Reaction rate remains stable as long as temperature and pressure are stable. E) none of the above Answer: D 49. Suppose a wall divides a playground, and twenty balls lie on the ground on the east side, while forty balls lie on the west side. If a child on the east side of the wall always tosses a ball over the wall at the same time a child on the west side tosses a ball over the wall, then A) equilibrium has been established. B) all balls will eventually end up on one side. C) equilibrium will be established once thirty balls are on each side. D) this system can never reach equilibrium. E) none of the above Answer: A 50. A chemical equilibrium exists when A) reactants are completely changed to products. B) there are equal amounts of reactants and products. C) the rate at which reactants form products becomes zero. D) the sum of reactant and product concentrations equals one mole. E) the rate at which reactants form products is the same as the rate at which products form reactants. Answer: E 51. A system is said to be in dynamic equilibrium when: A) there is no longer any net change in the concentrations of products or reactants. B) the forward and reverse reactions come to a halt. C) the sum of the concentrations of the reactants is equal to the sum of the concentrations of the products. D) you have let the reaction proceed for approximately 30 minutes and can assume there will be no more changes. E) none of the above Answer: A 52. Given N2(g) + 3 H2(g) ⇌ 2 NH3(g), which scenario will allow you to eventually reach an equilibrium mixture involving these chemicals? A) Place only N2 into a sealed vessel. B) Place only H2 into a sealed vessel. C) Place only NH3 into a sealed vessel. D) All of the above scenarios. E) none of the above Answer: C 53. For the reaction aA + bB ⇌ cC + dD, the equilibrium expression is: Answer: D 54. For the reaction 2A + B ⇌ 2C + 3D, the equilibrium expression is: Answer: D 55. The chemical equation that would generate the equilibrium expression Keq = [B]2[C]/[A]3 is ________. (Assume all substances are gases in this reaction.) A) C + 2B ⇌ 3A B) 3A ⇌ 2B + C C) A ⇌ B + C D) 1/2 B + C ⇌ 1/3 A E) none of the above Answer: B 56. For the reaction S2F6 ⇌ 2SF2 + F2, the equilibrium expression is: Answer: B 57. Which equilibrium constant represents a reaction that favors the formation of the products to the greatest extent? A) Keq = 100 B) Keq = 1.0 × 108 C) Keq = 1.0 × 10-3 D) Keq = 1.0 × 10-18 E) not enough information Answer: B 58. Which equilibrium constant represents a reaction that favors the reactants to the greatest extent? A) Keq = 100 B) Keq = 1.0 × 108 C) Keq = 1.0 × 10-3 D) Keq = 1.0 × 10-18 E) not enough information Answer: D 59. Which of the following is TRUE of a system for which Keq 1? A) It will take a short time to reach equilibrium. B) It will take a long time to reach equilibrium. C) The equilibrium favors the reverse reaction. D) The equilibrium favors the forward reaction. E) none of the above Answer: D 61. Identify the equation for which Keq = [Cu+]2[S2-]. A) Cu2S(s) ⇌ Cu+(aq) + 2 S2-(aq) B) CuS(s) ⇌ Cu2+(aq) + S2-(aq) C) 1/2 Cu2S(s) ⇌ Cu+(aq) + 1/2 S2-(aq) D) Cu2S(s) ⇌ 2 Cu+(aq) + S2-(aq) E) none of the above Answer: D 62. What must be TRUE for a reaction possessing a large equilibrium constant? A) The reaction rate is fast. B) The reaction rate is slow. C) The forward reaction is favored. D) The reverse reaction is favored. E) none of the above Answer: C 63. When writing the expression for an equilibrium constant, which type of substance IS included? A) solids B) pure liquids C) gases D) all of the above E) none of these Answer: C 64. For the reaction 2 H2O (l) ⇌ 2H2(g) + O2(g), the equilibrium expression is: Answer: B 65. For the reaction Cu2S(s) ⇌ 2Cu+(aq) + S2-(aq), the equilibrium expression is: Answer: C 66. For the reaction 2 A ⇌ B, the equilibrium concentrations are as follows: [A] = 0.056 M and [B] = 0.12 M. Calculate the equilibrium constant (Keq) for the reaction. A) 2.6 × 10-2 B) 0.26 C) 2.1 D) 38 E) none of the above Answer: D 67. For the reaction S2F6(g) ⇌ 2SF2(g) + F2(g), [SF2] = 0.18 M, [F2] = 0.54 M. The Equilibrium constant is: A) 0.44 B) 0.15 C) 2.3 D) 6.7 E) none of the above Answer: B 68. For the reaction S2F6(g) ⇌ 2SF2(g) + F2(g), the equilibrium concentrations are as follows: [S2F6] = 0.000430 M, [SF2] = 2.08 M, [F2] = 1.32 M. The equilibrium constant is: A) 7.53 × 10-5 B) 1.19 × 10-4 C) 8.43 × 103 D) 1.33 × 104 E) none of the above Answer: D 69. For the reaction Cu2(s) ⇌ 2Cu+(aq) + S2-(aq), the equilibrium concentrations are as follows: [Cu+] = 1.0 × 10-5 M, [S2-] = 1.0 × 10-2 M. The equilibrium constant is: A) 1.0 × 10-7. B) 1.0 × 107. C) 1.0 × 10-12. D) 1.0 × 10-9. E) none of the above Answer: C 70. For the reaction LiOH(s) ⇌ Li+(aq) + OH-(aq), Keq = 4.6 × 10-3, and the equilibrium concentration for hydroxide ion is [OH-] = 0.042 M. What is [Li+] at equilibrium? A) 0.11 M B) 0.0046 M C) 0.042 M D) An answer cannot be determined without [LiOH] value. E) none of the above Answer: A 71. For the reaction Ag2S(s) ⇌ 2 Ag+(aq) + S2-(aq), Keq = 2.4 × 10-4 and the equilibrium concentration of silver ion is [Ag+] = 2.5 × 10-1 M. What is [S2-] at equilibrium? A) 0.0038 B) 9.6 × 10-4 C) 2.6 × 102 D) 1.0 × 103 E) none of the above Answer: A 72. For the reaction Ag2S(s) ⇌ 2 Ag+(aq) + S2-(aq), Keq = 2.4 × 10-4, and the equilibrium concentration of sulfide ion is [S2-] = 0.0023 M. What is [Ag+] at equilibrium? A) 0.052 M B) 0.32 M C) 0.015 M D) 0.10 M E) none of the above Answer: B 73. Le Chatelier's Principle states that: A) a disturbing force must be applied to a system in order for it to reach equilibrium. B) when a system at equilibrium is disturbed, a new equilibrium constant is established. C) when a chemical system at equilibrium is disturbed, the system shifts in order to minimize the effect. D) when a chemical system is at equilibrium it is no longer possible to alter the system. E) none of the above Answer: C 74. For the reaction Ag2S(s) ⇌ 2 Ag+(aq) + S2-(aq), what happens to the equilibrium position if aqueous ammonium sulfide is added? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: A 75. For the reaction Ag2S(s) ⇌ 2 Ag+(aq) + S2-(aq), what happens to the equilibrium position if ammonium sulfate is added? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: C 76. For the reaction Ag2S(s) ⇌ 2 Ag+(aq) + S2-(aq), what happens to the equilibrium position if the amount of solid silver sulfide is doubled? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: C 77. For the reaction Ag2S(s) ⇌ 2 Ag+(aq) + S2-(aq), what happens to the equilibrium position if the amount of silver ion is halved? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: B 78. Consider the reaction: 2 N2O(g) ⇌ O2(g) + 2 N2(g). Which of the following will cause a shift in the equilibrium to the right? 1. Add more N2O 2. Remove O2 3. Remove N2 A) 1 and 2 only B) 1 and 3 only C) 2 and 3 only D) All of 1, 2, and 3 E) Neither 1, 2, or 3 Answer: D 79. Consider the reaction: 2 N2O(g) ⇌ O2(g) + 2 N2(g). Which of the following will cause a shift in the equilibrium to the left? 1. Remove N2O 2. Remove O2 3. Add N2 A) 1 and 2 only B) 1 and 3 only C) 2 and 3 only D) All of 1, 2, and 3 E) Neither 1, 2, or 3 Answer: B 80. We have the following reaction at equilibrium in a flask, CaSO4(s) ⇌ Ca2+(aq) + SO42+(aq) What will happen to [Ca2+] if additional CaSO4 is added to the flask? A) It will decrease. B) It will increase. C) It will not change. D) Cannot tell with the information provided. Answer: C 81. For the reaction 2 N2O(g) ⇌ O2(g) + 2 N2(g), what happens to the equilibrium position if the pressure increases? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: A 82. For the reaction H2(g) + Cl2(g) ⇌ 2 HCl(g), what happens to the equilibrium position if the pressure increases? A) shifts to the right B) shifts to the left C) does nothing D) doubles E) none of the above Answer: C 83. For the reaction 2 N2O(g) ⇌ O2(g) + 2 N2(g), what happens to the equilibrium position if the pressure decreases? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: B 84. For the reaction 2 N2O(g) ⇌ O2(g) + 2 N2(g), what happens to the equilibrium position if the volume decreases? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: A 85. For the reaction 2 N2O(g) ⇌ O2(g) + 2 N2(g), what happens to the equilibrium position if the volume increases? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: B 86. What happens to the equilibrium position of an exothermic reaction when you add heat? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: A 87. What happens to the equilibrium position of an exothermic reaction when you remove heat? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: B 88. What happens to the equilibrium position of an endothermic reaction when you add heat? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: B 89. What happens to the equilibrium position of an endothermic reaction when you remove heat? A) shifts to the left B) shifts to the right C) does nothing D) doubles E) halves Answer: A 90. Which compound is the most soluble? A) CuS, Ksp = 1.27 × 10-36 B) PbS, Ksp = 9.04 × 10-29 C) AgCl, Ksp = 1.77 × 10-10 D) AgI, Ksp = 8.51 × 10-17 E) not enough information Answer: C 91. Which compound is the least soluble? A) CuS, Ksp = 1.27 × 10-36 B) PbS, Ksp = 9.04 × 10-29 C) AgCl, Ksp = 1.77 × 10-10 D) AgI, Ksp = 8.51 × 10-17 E) not enough information Answer: A 92. What is the Ksp expression for the ionic compound Li2CO3? A) Ksp = [Li+] [CO32-] B) Ksp = [Li+]2 [CO32-] C) Ksp = 2[Li+] [CO32-] D) Ksp = [Li2CO3]3 E) none of the above Answer: B 93. What is the [Cu2+] at equilibrium, given CuS, Ksp = 1.27 × 10-36? A) 1.27 × 10-36 M B) 6.35 × 10-37 M C) 1.13 × 10-18 M D) 1.61 × 10-72 M E) not enough information Answer: C 94. What is the [Ag+] at equilibrium, given AgCl, Ksp = 1.77 × 10-10? A) 1.77 × 10-10 M B) 1.33 × 10-5 M C) 8.85 × 10-11 M D) 3.54 × 10-10 M E) not enough information Answer: B 95. What is the molar solubility, (S), of FeS if the Ksp = 5.9 × 10-19 for this substance? A) 1.2 × 10-18 M B) 5.9 × 10-19 M C) 7.7 × 10-10 M D) 3.5 × 10-37 M E) none of the above Answer: C 96. Which statement about activation energy is FALSE? A) Activation energy is an energy hump that normally exists between reactants and products. B) The higher the activation energy, the slower the reaction rate. C) The lower the activation energy, the faster the reaction rate. D) Increasing the temperature lowers the activation energy. E) All of the above are true. Answer: D 97. The effect of a catalyst is to: A) increase the number of collision between reactants. B) increase the temperature of the reactants whereby more products are formed. C) change the position of the equilibrium. D) change the stoichiometry of the reaction. E) lower the activation energy of a reaction whereby making it easier for the reactants to get over the energy hump. Answer: E 98. Comparing a reaction with a catalyst to the same reaction without the catalyst, each of the following statements is true EXCEPT A) The rate for the reaction with a catalyst is faster. B) The products are the same. C) The catalyzed reaction follows a different pathway. D) Both reactions would have the same value for the equilibrium constant. E) The activation energy is the same for both the catalyzed and uncatalyzed reaction. Answer: E 99. Which statement below is FALSE? A) The rate of a reaction can be increased by increasing concentrations of reactants. B) The rate of a reaction can be increased by altering the temperature. C) The rate of a reaction can be increased by adding a catalyst. D) A catalyst alters the equilibrium constant. E) All of the above are true. Answer: D 100. What happens to the equilibrium constant when a catalyst is added to the reaction mixture? A) increases B) decreases C) does not change D) varies E) none of the above Answer: C 101. Which of the following is FALSE about enzymes? A) They act as biological catalysts. B) They lower the activation energy of biological reactions. C) They increase the temperature of biological reactions to speed them up. D) They are highly specific in their catalytic activity. E) none of the above Answer: C Algorithmic Questions 102. Calculate the equilibrium constant for the reaction below given that [Cl2] = 0.11 M, [H2] = 0.15 M, and [HCl] = 0.95 M at equilibrium. Given: Cl2(g) + H2(g) → 2HCl(g) A) 0.017 B) 0.018 C) 58 D) 55 E) none of the above Answer: D 103. Calculate the concentration of NO2 in an equilibrium mixture given that the concentration of N2O4 = 0.200 M. and Keq = 45.5 for the reaction: 2 NO2(g) ⇌ N2O4(g). A) 0.0663 M B) 0.00440 M C) 227.3 M D) 15.1 M E) none of the above Answer: A 104. Calculate [M+] at equilibrium given that the Ksp = 3.7 × 10-2 for the reaction MX(s) → M+ + X-. A) 0.0185 M B) 0.0 M C) 0.19 M D) not enough information given E) none of the above Answer: C 105. What is the concentration of the Mg2+ ion in solution when [CO32-] = 0.25 M given that the Ksp = 6.82 × 10-6 for the following reaction: MgCO3(s) ⇌ Mg2+(aq) + CO32-(aq)? A) 5.2 × 10-2 B) 3.7 × 104 C) 2.7 × 10-5 D) 19.2 E) none of the above Answer: C 106. What is the value for the Ksp for a compound MX(s) if at equilibrium [M+] = 1.0 × 10-3 M? A) 0.0020 B) 1.0 × 10-6 C) 1.0 × 10-3 D) not enough information E) none of the above Answer: B Chapter 16 Oxidation and Reduction True/False Questions 1. Cars are being developed that run on hydrogen gas and the only emission is water. Answer: True 2. Fuel cells are based on the tendency of some elements to gain electrons from gasoline. Answer: False 3. Reactions involving the transfer of electrons are called redox reactions. Answer: True 4. Oxidation can be defined as the gain of oxygen atoms by another element. Answer: True 5. Reduction can be defined as the gain of oxygen atoms by another element. Answer: False 6. Redox reactions must involve the gain or loss of oxygen atoms. Answer: False 7. Oxidation and reduction cannot both occur in the same chemical reaction. Answer: False 8. The oxidizing agent is the substance being reduced. Answer: True 9. The reducing agent is reduced during the reaction. Answer: False 10. Reduction is the gain of electrons. Answer: True 11. Oxidation is the loss of electrons. Answer: True 12. The sum of the oxidation numbers of all atoms in K2Cr2O7 equals zero. Answer: True 13. The oxidation number of a chlorine atom is -1. Answer: False 14. The oxidation number of sodium in NaI is +1. Answer: True 15. The oxidation number of sulfur in SO3 is -6. Answer: False 16. The oxidation number of manganese in MnO41- is +7. Answer: True 17. The reaction 2 NO2 → N2O4 would not be considered a redox reaction. Answer: True 18. The half-reaction 2 Br1- → Br2 + 2 e- is balanced with respect to mass but it is not balanced with respect to charge. Answer: False 19. Given that the Activity Series shown below is accurate, then Li(s) + K+(aq) → Li+(aq) + K(s) is a spontaneous reaction. Answer: True 20. Most acids dissolve metals by the oxidation of H+ ions to hydrogen gas. Answer: False 21. Ca2+(aq) + 2Na (s) → Ca (s) + 2 Na+(aq) is a spontaneous reaction. Answer: False 22. Gold metal is found at the bottom of the activity series of metals since it is the most difficult metal to oxidize. Answer: True 23. It can be shown that copper metal lies below H2 on the activity series of metals. This means that copper will dissolve in hydrochloric acid. Answer: False 24. An electrochemical cell is based on the coupling of a spontaneous redox reaction. Answer: True 25. Oxidation occurs at the cathode. Answer: False 26. The cathode is the electrode at which reduction occurs. Answer: True 27. Electrical current can be used to drive a nonspontaneous redox reaction. Answer: True 28. A galvanic cell is a spontaneous electrochemical cell. Answer: True 29. The driving force that causes electrons to flow through a wire is called current. Answer: False 30. Flashlight batteries are called dry cells. Answer: True 31. Alkaline batteries are used in automobiles. Answer: False 32. To achieve the largest battery voltage possible, the battery should be assembled from a metal high on the activity series list with a metal ion low on the activity series list. Answer: True 33. An electrolytic cell is a spontaneous redox reaction. Answer: False 34. A spontaneous redox reaction can be used to produce electrical current. Answer: True 35. Electrolysis is used to recover many metals from their oxide ores. Answer: True 36. Corrosion of metals may be prevented by keeping them dry at all times. Answer: True 37. The rusting of iron is an example of the process known as corrosion. Answer: True 38. Rusting of iron requires the presence of both oxygen and water. Answer: True 39. A sacrificial electrode works by being reduced which prevents the metal from being oxidized. Answer: False Multiple Choice Questions 40. Which fact about fuel cells is FALSE? A) Fuel cell automobiles are powered by water and the only emission is hydrogen. B) Fuel cells are based on the tendency of some elements to gain electrons from other elements. C) Fuel cell automobiles are whisper quiet. D) Fuel cell automobiles are environmentally friendly. E) all of the above Answer: A 41. Oxidation typically involves: A) the loss of electrons. B) the loss of oxygen. C) the gain of electrons. D) the gain of water. E) none of the above Answer: A 42. Reduction typically involves: A) the loss of electrons. B) the gain of oxygen. C) the gain of electrons. D) the gain of water. E) none of the above Answer: C 43. The reducing agent typically: A) gains electrons. B) always remains unchanged during a reaction. C) is the oxidized substance. D) is itself reduced. E) none of the above Answer: C 44. The oxidizing agent typically: A) loses electrons. B) gains oxygen. C) is the reactant that is reduced. D) is oxidized. E) none of the above Answer: C 45. Which of the following are typically TRUE of an oxidizing agent? 1. It causes oxidation. 2. It gains electron(s). 3. It is the reduced substance. A) 1 and 2 only B) 1 and 3 only C) 2 and 3 only D) All of 1, 2, and 3 E) Neither 1, 2, or 3 Answer: D 46. Which of the following are typically TRUE of a reducing agent? 1. It causes reduction. 2. It gains electron(s). 3. It is the oxidized substance. A) 1 and 2 only B) 1 and 3 only C) 2 and 3 only D) All of 1, 2, and 3 E) Neither 1, 2 or 3 Answer: B 47. Identify the substance being oxidized in the following reaction: CH4 + 2O2 → CO2 + 2H2O. A) CH4 B) O2 C) CO2 D) H2O E) none of the above Answer: A 48. Identify the substance being reduced in the following reaction: CH4 + 2O2 → CO2 + 2H2O. A) CH4 B) O2 C) CO2 D) H2O E) none of the above Answer: B 49. Identify the reducing agent in the following reaction: CH4 + 2O2 → CO2 + 2H2O. A) CH4 B) O2 C) CO2 D) H2O E) none of the above Answer: A 50. Identify the oxidizing agent in the following reaction: CH4 + 2O2 → CO2 + 2H2O. A) CH4 B) O2 C) CO2 D) H2O E) none of the above Answer: B 51. For the reaction Si (s) + O2(g) → SiO2(g), the reducing agent is A) Si. B) O2. C) SiO2. D) O. E) none of the above Answer: A 52. In the following reaction, Mg (s) + Cu2+(aq) → Mg2+(aq) + Cu (s): A) Mg is the reducing agent and Cu is the oxidizing agent. B) Mg2+ is the reducing agent and Cu is the oxidizing agent. C) Cu is the reducing agent and Mg2+ is the oxidizing agent. D) Cu2+ is the reducing agent and Mg is the oxidizing agent. E) Mg is the reducing agent and Cu2+ is the oxidizing agent. Answer: E 53. In the following reaction, Zn (s) + CuSO4(aq) → ZnSO4(aq) + Cu (s) A) Zn is the reducing agent and CuSO4 is the oxidizing agent. B) CuSO4 is the reducing agent and Zn is the oxidizing agent. C) ZnSO4 is the reducing agent and Cu is the oxidizing agent. D) Cu2+ is the reducing agent and Zn2+ is the oxidizing agent. E) none of the above Answer: A 54. The oxidation number of Cr in Cr2O72- is A) +2. B) -2. C) +7. D) +6. E) none of the above Answer: D 55. What is the oxidation state of the underlined element in the compound: H2SO4? A) +1 B) +2 C) -2 D) +6 E) +4 Answer: C 56. What is the oxidation state of the underlined element in the compound: H2SO4? A) +1 B) +2 C) -2 D) +6 E) +4 Answer: D 57. What is the oxidation state of the underlined element in the compound: CO2? A) +1 B) +2 C) -2 D) +4 E) +6 Answer: D 58. What is the oxidation state of the underlined element in the reaction: NaHCO3 + HCl → NaCl + CO2 + H2O A) 0 B) +1 C) -1 D) +2 E) -2 Answer: C 59. What is the oxidation state of the underlined element in the reaction: NaHCO3 + HCl → NaCl + CO2 + H2O A) 0 B) +1 C) -1 D) +2 E) -2 Answer: E 60. What is the oxidation state of the underlined element in the reaction: NaHCO3 + HCl → NaCl + CO2 + H2O A) 0 B) +1 C) -1 D) +2 E) -2 Answer: B 61. What is the oxidation state of the underlined element in the reaction: Cl2 + Mg → MgCl2 A) 0 B) +2 C) -2 D) +4 E) -4 Answer: A 62. What is the oxidation state of nitrogen in N2O3? A) 0 B) +1 C) +2 D) +3 E) +6 Answer: D 63. What is the oxidation state of sulfur in SO32-? A) 0 B) -2 C) +3 D) +4 E) +6 Answer: D 64. The oxidation state of Na in Na2SO4 is: A) +1 B) +2 C) +4 D) -1 E) none of the above Answer: A 65. The oxidation state of Mn in KMnO4 is: A) +1 B) -1 C) +5 D) +7 E) none of the above Answer: D 66. Which substance below would contain a nitrogen atom with the highest oxidation number of all those shown? A) NH41+ B) N2 C) NO2 D) NO31- E) NH3 Answer: D 67. Assign the oxidation state of each atom in potassium chlorate, KClO3. A) K = +1, Cl = +1, O = -2 B) K = -1, Cl = -1, O = +2 C) K = +1, Cl = +5, O = -2 D) K = +1, Cl = -1, O = 0 E) K = -1, Cl = +1, O = 0 Answer: C 68. Assign the oxidation state of each atom in sodium sulfate, Na2SO4. A) Na = +1, S = +4, O = -2 B) Na = +1, S = -2, O = +4 C) Na = +2, S = +6, O = -2 D) Na = +1, S = +6, O = -2 E) Na = +2, S = -2, O = 0 Answer: D 69. Oxidation involves which of the following? 1. Loss of electron(s). 2. Gain of electron(s). 3. Increase in oxidation state. A) 1 only B) 2 only C) 3 only D) 1 and 3 only E) 2 and 3 only Answer: D 70. Reduction involves which of the following? 1. Loss of electron(s). 2. Gain of electron(s). 3. Decrease in oxidation state. A) 1 only B) 2 only C) 3 only D) 1 and 2 only E) 2 and 3 only Answer: E 71. What must be done to the following half-reactions before they can be added together? Mn (s) → Mn2+(aq) + 2e- Fe3+(aq) + 3 e- → Fe (s) A) Double the Mn half-reaction. B) Double the Mn half-reaction and triple the Fe half-reaction. C) Triple the Mn half-reaction and double the Fe half-reaction. D) Add H+ ions to the left-side of the Mn reaction. E) none of the above Answer: C 72. What is the balanced oxidation half-reaction for the following unbalanced redox reaction: Ca(s) + Ag+(aq) → Ca2+(aq) + Ag(s) A) Ca → Ca2+ + 2 e- B) Ag+ → Ag + e- C) 2 e- + Ca → Ca2+ D) 2 Ag+ + 2 e- → 2Ag E) none of the above Answer: A 73. What is the balanced reduction half-reaction for the following unbalanced redox reaction: Ca(s) + Ag+(aq) → Ca2+(aq) + Ag(s) A) Ca → Ca2+ + 2 e- B) Ag+ → Ag + 1 e- C) 2 e- + Ca → Ca2+ D) 2Ag+ + 2 e- → 2Ag E) none of the above Answer: D 74. Balance the redox reaction: Br-(aq) + Cr2O72-(aq) → Cr3+ + Br2(l) Answer: B 75. If you properly balance the following half reaction in acid solution, how many electrons would appear on the product side of the equation? NO(g) → NO31-(aq) A) 1 B) 2 C) 3 D) 5 E) none of the above Answer: C 76. Balance the following half reaction in acid solution: MnO4- → Mn2+(aq) A) MnO4- → Mn2+ + 3 e- B) MnO4- + 8 H+ → Mn2+ + 4 H2O C) MnO4- + 8 H+ → Mn2+ + 4 H2O +5 e- D) MnO4- + 8 H+ + 5 e- → Mn2+ + 4 H2O E) none of the above Answer: D 77. If you properly balance the following half reaction in base solution, how many electrons would appear on the product side of the equation? Al (s) → Al(OH)41-(aq) A) 2 B) 3 C) 4 D) 5 E) none of the above Answer: B 78. Balance the following half reaction in base solution: H2O (l) → H2(g) A) 2H2O (l) + 2 e- → H2(g) + 2 OH-(aq) B) 2H2O (l) → 2H2(g) + 2 e- + O2 C) 2H2O (l) → H2(g) + 2 H+ + 2e- D) H2O (l) → 2H+ + 2OH- E) 2H2O (l) → H2(g) + 2OH-(aq) + 5 e- Answer: A 79. What is the balanced oxidation half-reaction for the following unbalanced redox reaction? Ca(s) + Ag+(aq) → Ca2+(aq) + Ag(s) A) Ca → Ca2+ + 2 e- B) Ag+ → Ag + e- C) 2 e- + Ca → Ca2+ D) 2 Ag+ + 2 e- → 2Ag E) none of the above Answer: A 80. From the activity list included in this problem, which element/ion is the most easily oxidized? A) Na B) Ca C) Na+ D) Li E) Li+ Answer: D 81. From the activity list included in this problem, which element/ion is the most difficult to oxidize? A) Na B) Ca C) Na+ D) Li E) Li+ Answer: A 82. From the activity list included in this problem, which element/ion is the most difficult to reduce? A) Na B) Ca C) Na+ D) Li E) Li+ Answer: E 83. From the activity list included in this problem, which element/ion is the easiest to reduce? A) Na B) Ca C) Na+ D) Li E) Li+ Answer: C 84. From the activity list included in this problem, which element/ion will spontaneously react with K+? A) Na B) Ca C) Na+ D) Li E) Li+ Answer: D 85. From the activity list included in this problem, which element/ion will spontaneously react with Ca? A) Na B) K+ C) Na+ D) Li E) Li+ Answer: C 86. From the activity list included in this problem, which element will not dissolve in dilute hydrochloric acid? A) Sn B) Pb C) H2 D) Cu E) none of the above Answer: D 87. From the activity list included in this problem, which element will displace Pb2+ ions from solution? A) Sn B) Pb C) H2 D) Cu E) none of the above Answer: A 88. From the activity list included in this problem, which element will react with Cu? A) Sn B) Pb C) H2 D) Cu E) none of the above Answer: E 89. Using the activity list included in this problem, which element/ion listed below is the most easily oxidized? A) Sn+2 B) Pb C) H2 D) Cu+2 E) none of the above Answer: B 90. Using the activity list included in this problem, which element/ion is the most resistant to oxidation? A) Sn+2 B) Pb C) H2 D) Cu+2 E) none of the above Answer: C 91. Using the activity list included in this problem, which element/ion is the most resistant to reduction? A) Sn+2 B) Pb C) H2 D) Cu+2 E) none of the above Answer: A 92. From the activity list included in this problem, which element/ion is the easiest to reduce? A) Sn+2 B) Pb C) H2 D) Cu+2 E) none of the above Answer: D 93. In an electrochemical cell, which of the following statements is FALSE? A) The anode is electrode where oxidation occurs. B) A salt bridge provides electrical contact between the half-cells. C) The cathode is the electrode where reduction occurs. D) A spontaneous electrochemical cell is called a galvanic cell. E) All of the above are true. Answer: E 94. In an electrochemical cell, which of the following statements is FALSE? A) Oxidation occurs at the anode. B) Reduction occurs at the cathode. C) Electrons flow through the salt bridge to complete the cell. D) A spontaneous electrochemical cell is called a voltaic cell. E) All of the above are true. Answer: C 95. Which battery system is based on half reactions involving zinc metal and manganese dioxide? A) alkaline batteries B) fuel cells C) lead-acid storage batteries D) dry-cell batteries E) none of the above Answer: D 96. Which battery system is completely rechargeable? A) alkaline batteries B) fuel cells C) lead-acid storage batteries D) dry-cell batteries E) none of the above Answer: C 97. In electrolysis: A) a spontaneous redox reaction produces electricity. B) a nonspontaneous redox reaction is forced to occur by applying an electric current. C) only pure, drinkable water is produced. D) you have a cell which reverses the flow of ions. E) none of the above Answer: B 98. Corrosion is the: A) oxidation of nonmetals. B) loss of electrons. C) oxidation of metals. D) formation of an insoluble hydroxide. E) none of the above Answer: C 99. Corrosion can be prevented by all of the following EXCEPT: A) painting. B) galvanizing. C) sacrificial anode. D) sacrificial cathode. E) none of the above Answer: D 100. From the activity list included in this problem, which element below would serve as a sacrificial electrode for iron? A) Zn B) Fe C) Ni D) all of these E) none of these Answer: A Essay Questions 101. Distinguish between a galvanic (voltaic) cell and an electrolytic cell. Answer: In a galvanic (voltaic)cell, an electric current is produced as a result of a spontaneous redox reaction. An electrolytic cell uses electric current to produce a redox reaction. The resulting reaction is nonspontaneous. 102. Suggest two methods to reduce corrosion of a metal such as iron and briefly explain how each method works. Answer: 1. Galvanizing: This is a process in which the metal such as iron is coated with zinc. Zinc is higher on the activity series than iron and is more readily oxidized than iron. The zinc oxide formed also acts as a protective coating. 2. Sacrificial anode: These are metals that are more readily oxidized than iron which in turn prevent iron from being oxidized. Test Bank for Introductory Chemistry Nivaldo J. Tro 9780321741028, 9780321687937, 9781256112938, 9781256161066, 9780134302386, 9780321910073
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