Redox Review Chem II 1. What is the sum of the oxidation numbers of the atoms in the compound CO2? A) 0 B) 2 C) 4 D) +4 2. In which substance does phosphorus have a +3 oxidation state? A) P4O10 B) PCl5 C) Ca3(PO4)2 D) KH2PO3 3. What is the oxidation number of iodine in KIO4? A) +1 B) 1 C) +7 D) 7 4. Given the reaction that occurs in an electrochemical cell: Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s) During this reaction, the oxidation number of Zn changes from A) 0 to +2 B) 0 to 2 C) +2 to 0 D) 2 to 0 5. Which polyatomic ion has a charge of 3? A) chromate ion B) oxalate ion C) phosphate ion D) thiocyanate ion 6. What is the oxidation number of Pt in K2PtCl6? A) 2 B) +2 C) 4 D) +4 7. In which compound does carbon have an oxidation state of 4? A) CO B) CO2 C) CCl4 D) CH4 8. In which substance does chlorine have an oxidation number of +1? A) Cl2 B) HCl C) HClO D) HClO2 9. What is the oxidation number of chromium in K2Cr2 O7? A) +12 B) +2 C) +3 D) +6 10. Which statement correctly describes a redox reaction? Ms. Mosley A) The oxidation half-reaction and the reduction half-reaction occur simultaneously. B) The oxidation half-reaction occurs before the reduction half-reaction. C) The oxidation half-reaction occurs after the reduction half-reaction. D) The oxidation half-reaction occurs spontaneously but the reduction half-reaction does not. 11. When a redox reaction occurs, there must be a transfer of A) electrons B) neutrons C) protons D) ions 12. A redox reaction always involves A) a change in oxidation number B) a change of phase C) the transfer of protons D) the formation of ions 13. In the reaction Mg + ZnCI2 MgCI2 + Zn, which is true of the magnesium? A) It is oxidized by losing electrons. B) It is oxidized by gaining electrons. C) It is reduced by losing electrons. D) It is reduced by gaining electrons. 14. Which changes occur when Pt 2+ is reduced? A) The Pt 2+ gains electrons and its oxidation number increases. B) The Pt 2+ gains electrons and its oxidation number decreases. C) The Pt 2+ loses electrons and its oxidation number increases. D) The Pt 2+ loses electrons and its oxidation number decreases.
15. In the reaction Al 0 + Cr 3+ Al 3+ + Cr 0, the species oxidized is A) Al 0 B) Cr 3+ C) Al 3+ D) Cr 0 16. In the reaction: Pb + 2 Ag + Pb 2+ + 2 Ag, the Ag + is A) reduced, and the oxidation number changes from +1 to 0 B) reduced, and the oxidation number changes from +2 to 0 C) oxidized, and the oxidation number changes from 0 to +1 D) oxidized, and the oxidation number changes from +1 to 0 17. In the reaction Co 0 + Cu 2+ Co 2+ + Cu 0, which specie is reduced? A) Co 0 B) Cu 0 C) Co 2+ D) Cu 2+ 18. The transfer of which particle is required for a redox reaction to occur? A) electron B) ion C) neutron D) proton 19. What species is reduced in the reaction below? Zn 0 + 2 Ag + Zn 2+ + 2 Ag 0? A) Zn 0 B) Ag 0 C) Zn 2+ D) Ag + 20. In the reaction Pb + 2 Ag + Pb 2+ + 2 Ag, the oxidizing agent is A) Ag + B) Ag C) Pb D) Pb 2+ 21. The oxidation number of a reducing agent can change from A) 1 to 3 B) 2 to 1 C) 3 to 1 D) 4 to 3 22. Which ion is most easily reduced? A) Zn 2+ B) Mg 2+ C) Co 2+ D) Ca 2+ 23. Which is the oxidizing agent in the reaction 2 Fe 2+ + Cl2 2 Fe 3+ + 2 Cl? A) Fe 2+ B) Cl2 C) Fe 3+ D) Cl 24. When a substance is oxidized, it A) loses protons B) gains protons C) acts as an oxidizing agent D) acts as a reducing agent 25. In the reaction Mg + Cl2 MgCl2, the correct half-reaction for the oxidation that occurs is A) Mg + 2e Mg 2+ B) Cl2 + 2e 2Cl C) Mg Mg 2+ + 2e D) Cl2 2Cl + 2e 26. Given the equation: C(s) + H2O(g) CO(g) + H2(g) Which species undergoes reduction? A) C(s) B) H + C) C 2+ D) H2(g) 27. Given the reaction: Fe(s) + Cu 2+ (aq) Fe 2+ (aq) + Cu(s) Which half-reaction correctly shows the oxidation that occurs? A) Fe(s) Fe 2+ (aq) + 2e B) Fe(s) + 2e Fe 2+ (aq) C) Cu 2+ (aq) Cu(s) + 2e D) Cu 2+ (aq) + 2e Cu(s)
28. Given the balanced equation representing a redox reaction: 2Al + 3Cu 2+ 2Al 3+ + 3Cu Which statement is true about this reaction? A) Each Al loses 2e and each Cu 2+ gains 3e. B) Each Al loses 3e and each Cu 2+ gains 2e. C) Each Al 3+ gains 2e and each Cu loses 3e. D) Each Al 3+ gains 3e and each Cu loses 2e. 29. Which half-reaction equation represents the reduction of an iron(ii) ion? A) Fe 2+ Fe 3+ + e B) Fe 2+ + 2e Fe C) Fe 3+ + e Fe 2+ D) Fe Fe 2+ + 2e 30. Given the reaction for the corrosion of aluminum: 4 Al + 3 O2 2 Al2O3 Which half-reaction correctly represents the oxidation that occurs? A) Al + 3e Al 3+ B) Al Al 3+ + 3e C) O2+ 4e 2 O 2 D) O2 2 O 2 + 4e 31. Given the reaction: Zn(s) + 2 HCl(aq) ZnCl2(aq) + H2(g) Which equation represents the correct oxidation half-reaction? A) Zn(s) Zn 2+ + 2e B) 2 H + 2e H2(g) C) Zn 2+ + 2e Zn(s) D) 2 Cl Cl2(g) + 2e 32. Given the reaction: Cu(s) + 4 HNO3(aq) Cu(NO3)2(aq) + 2 NO2(g) + 2 H2O( ) As the reaction occurs, what happens to copper? A) It undergoes reduction and its oxidation number decreases. B) It undergoes reduction and its oxidation number increases. C) It undergoes oxidation and its oxidation number decreases. D) It undergoes oxidation and its oxidation, number increases. 33. Given the reaction: 2 NaCl + 2 H2O 2 NaOH + H2 + Cl2 Which electronic equation correctly represents the oxidation that occurs in this reaction? A) 2 Na 0 2 Na + + 2e B) 2 Cl Cl2 0 + 2e C) 2 H + + 2e H2 0 D) O2 0 + 2e 2 O 2 34. Given the reaction: 2 Al 0 (s) + 3 Ni 2+ (aq) 2 Al 3+ (aq) + 3 Ni 0 (s) What is the total number of moles of electrons lost by 2 moles of Al 0 (s)? A) 6 B) 2 C) 3 D) 8 35. Given the reaction: Zn(s) + 2 HCl(aq) ZnCl2(aq) + H2(g) Which statement correctly describes what occurs when this reaction takes place in a closed system? A) Atoms of Zn(s) lose electrons and are oxidized. B) Atoms of Zn(s) gain electrons and are reduced. C) There is a net loss of mass. D) There is a net gain of mass.
36. Which equation represents a redox reaction? A) 2 Na + + S 2 Na2S B) H + + C2H3O2 HC2H3O2 C) NH3 + H + + Cl NH4 + + Cl D) Cu + 2 Ag + + 2 NO3 2 Ag + Cu 2+ + 2 NO3 37. Which equation represents an oxidation-reduction reaction? A) B) C) D) 38. In which reaction are electrons transferred from one reactant to another reactant? A) 2Ca(s) + O2 (g) 2CaO(s) B) AgNO3 (aq) + KCl(aq) AgCl(s) + KNO3 (aq) C) HCl(aq) + NaOH(aq) NaCl(aq) + H2O( ) D) H3O + (aq) + OH (aq) 2H2O( ) 39. Which reaction is an example of an oxidation-reduction reaction? A) AgNO3 + KI AgI + KNO3 B) Cu + 2 AgNO3 Cu(NO3)2 + 2 Ag C) 2 KOH + H2SO4 K2SO4 + 2 H2O D) Ba(OH)2 + 2 HCl BaCl2 + 2 H2O 40. Which metal is more active than H2? A) Ag B) Au C) Cu D) Pb 41. According to Reference Table J, which will reduce Mg 2+ to Mg(s)? A) Fe(s) B) Ba(s) C) Pb(s) D) Ag(s) 42. Based on the Activity Series,, which ion will oxidize Pb to Pb 2+? A) Cu 2+ B) Ni 2+ C) Fe 2+ D) Zn 2+ 43. Which metal reacts spontaneously with a solution containing zinc ions? A) magnesium B) nickel C) copper D) silver 44. Under standard conditions, which metal will react with 0.1 M HCl to liberate hydrogen gas? A) Ag B) Au C) Cu D) Mg 45. According to Reference Table J, which halogen will react spontaneously with Au(s) to produce Au 3+? A) Br2 B) F2 C) I2 D) Cl2 46. The half-reaction 2 H + (aq) + 2e H2(g) will occur when H + (aq) reacts with A) Pb(s) B) Cu(s) C) Hg( ) D) Ag(s) 47. When an equation is correctly balanced, it must show conservation of A) charge but not of mass B) mass but not of charge C) both charge and mass D) neither charge nor mass 48. Which half-reaction for the reduction of Al 3+ to Al is correctly balanced? A) Al 3+ + 3e Al B) Al 3+ + 3e 3 Al C) Al 3+ Al + 3e D) Al 3+ 3 Al + 3e 49. Which half-reaction shows both the conservation of mass and the conservation of charge? A) Cl2 + 2e 2 Cl B) Cl2 Cl + 2e C) 2 Br + 2e Br2 D) Br Br2 + 2e 50. Given the unbalanced ionic equation: When this equation is balanced, both Fe 3+ and Fe have a coefficient of A) 1, because a total of 6 electrons is transferred B) 2, because a total of 6 electrons is transferred C) 1, because a total of 3 electrons is transferred D) 2, because a total of 3 electrons is transferred
51. Which equation shows conservation of charge? A) Fe Fe 2+ + e B) Fe + 2e Fe 2+ C) Fe Fe 2+ + 2e D) Fe + 2e Fe 3+ 52. A chemical reaction always demonstrates the conservation of what? A) temperature B) volume C) matter D) nothing 53. Which half-reaction shows conservation of charge? A) Cu + e Cu + B) Cu 2+ + 2e Cu C) Cu + Cu + e D) Cu 2+ Cu + 2e 54. When the reaction is completely balanced using smallest whole numbers, the coefficient of H2O will be A) 1 B) 2 C) 3 D) 4 55. Which redox equation is correctly balanced? A) Al + 2 H + Al 3+ + H2 B) Zn + 2 H + Zn 2+ + H2 C) Cr + Ag + Cr 3+ + Ag D) Cu + Ag + Cu 2+ + Ag 56. Given the unbalanced equation: When the equation is correctly balanced using smallest whole numbers, the coefficient of Ag + is A) 5 B) 2 C) 3 D) 4 57. Given the reaction: When the equation is correctly balanced using smallest whole numbers, the sum of the coefficients will be A) 10 B) 7 C) 5 D) 4
58. Given the unbalanced equation: When the equation is correctly balanced using smallest whole number coefficients, the coefficient of HCl is A) 1 B) 2 C) 3 D) 4 59. Which energy conversion occurs in a voltaic cell? A) chemical energy to electrical energy B) chemical energy to nuclear energy C) electrical energy to chemical energy D) nuclear energy to electrical energy 60. Which substance functions as the electrolyte in an automobile battery? A) PbO2 B) PbSO4 C) H2SO4 D) H2O 61. Which half-reaction can occur at the anode in a voltaic cell? A) Ni 2+ + 2e - Ni B) Sn + 2e - Sn 2+ C) Zn Zn 2+ + 2e - D) Fe 3+ Fe 2+ + e - 62. Given the lead-acid battery reaction: As the lead-acid battery discharges, sulfuric acid is a A) reactant, with decreasing concentration B) reactant, with increasing concentration C) product, with decreasing concentration D) product, with increasing concentration
63. Base your answer to the following question on the diagram of the voltaic cell below. When the switch is closed, in which half-cell does oxidation occur? 64. Which statement is true for any electrochemical cell? A) Oxidation occurs at the anode, only. B) Reduction occurs at the anode, only. C) Oxidation occurs at both the anode and the cathode. D) Reduction occurs at both the anode and the cathode. 65. What occurs during discharge in the lead-acid battery reaction below? Pb + PbO2 + 2 H2SO4 «2 PbSO4 + 2 H2O A) Both Pb and Pb 4+ undergo oxidation. B) Both Pb and Pb 4+ undergo reduction. C) Pb is oxidized and Pb 4+ is reduced. D) Neither the Pb nor the Pb 4+ is oxidized or reduced. 66. Given the redox reaction: Which species is oxidized during discharge? A) B) C) D)
67. Given the nickel-cadmium battery reaction: What occurs during discharge in the nickel-cadmium battery? A) is reduced to B) is reduced to C) is oxidized to D) is oxidized to 68. Base your answer to the following question on the diagram of the chemical cell at 298 K and on the equation below. In the given reaction, the Ag + ions A) gain electrons B) lose electrons C) gain protons D) lose protons 69. Given the equation for the overall reaction in a lead-acid storage battery: 71. The equation below represents the reaction occurring in a nickel-cadmium battery. 2 NiO(OH)3 + Cd + 2 H2O 2 Ni(OH)2 + Cd(OH)2 Which reaction occurs at the cathode? A) reduction of Cd B) oxidation of Cd C) reduction of NiOOH D) oxidation of NiOOH 72. Given the balanced equation representing the reaction occurring in a voltaic cell: Zn(s) + Pb 2 + (aq) Zn 2 + (aq) + Pb(s) In the completed external circuit, the electrons flow from A) Pb(s) to Zn(s) B) Pb 2+ (aq) to Zn 2+ (aq) C) Zn(s) to Pb(s) D) Zn 2+ (aq) to Pb 2+ (aq) Which occurs during the charging of the battery? A) The concentration of decreases and the number of moles of increases. B) The concentration of decreases and the number of moles of increases. C) The concentration of increases and the number of moles of decreases. D) The concentration of increases and the number of moles of decreases. 70. Given the reaction for the nickel-cadmium battery: 2 NiO(OH)3 + Cd + 2 H2O 2 Ni(OH)2 + Cd(OH)2 Which species is oxidized during the discharge of the battery? A) Ni 3+ B) Ni 2+ C) Cd D) Cd 2+ 73. What is the electron flow in a wire connecting the Zn and Cu electrodes of a zinc-copper chemical cell at standard conditions? A) from negative Zn to positive Cu B) from positive Zn to negative Cu C) from negative Cu to positive Zn D) from positive Cu to negative Zn
74. Where does oxidation occur in an electrochemical cell? A) at the cathode in both an electrolytic cell and a voltaic cell B) at the cathode in an electrolytic cell and at the anode in a voltaic cell C) at the anode in both an electrolytic cell and a voltaic cell D) at the anode in an electrolytic cell and at the cathode in a voltaic cell 75. The diagram below represents a chemical cell at 298 K. When the switch is closed, electrons flow from A) Al(s) to Ni(s) B) Ni(s) to Al(s) C) Al 3+ (aq) to Ni 2+ (aq) D) Ni 2+ (aq) to Al 3+ (aq) 76. Which procedure requires the use of an external electric current to force a redox reaction to occur? A) polymerization B) distillation C) electrolysis D) saponification 77. What occurs when an electrolytic cell is used for silver-plating a spoon? A) A chemical reaction produces an electric current. B) An electric current produces a chemical reaction. C) An oxidation reaction takes place at the cathode. D) A reduction reaction takes place at the anode. 78. Which statement best describes the reaction represented by the equation below? 2 NaCl + 2 H2O + electricity Cl2 + H2 + 2 NaOH A) The reaction occurs in a chemical cell and releases energy. B) The reaction occurs in a chemical cell and absorbs energy. C) The reaction occurs in an electrolytic cell and releases energy. D) The reaction occurs in an electrolytic cell and absorbs energy. 79. Which energy transformation occurs when an electrolytic cell is in operation? A) chemical energy electrical energy B) electrical energy chemical energy C) light energy heat energy D) light energy chemical energy 80. Which half-reaction occurs at the negative electrode in an electrolytic cell in which an object is being plated with silver? A) Ag 0 + 1e Ag + B) Ag 0 Ag + + 1e C) Ag + + 1e Ag 0 D) Ag + Ag 0 + 1e