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1. Which half–cell reaction correctly represents reduction? A) B) C) D) E) Sn4+ ® Sn2+ + 2e – Sn2+ ® Sn4+ + 2e – Sn4+ + 2e – ® Sn2+ Sn2+ + 2e – ® Sn4+ Sn4+ + Sn2+ ® Sn6+ + 2e – 2. 6. In the half–cell reaction Ca ®Ca2+ + 2e –, which is true of the calcium atom? A) B) C) D) E) It gains protons It loses protons It gains electrons It loses electrons It loses an electron and gains a proton 7. Which half–reaction correctly represents oxidation? A) B) C) D) E) In the electrochemical cell, Co/Co 2+||Sn 2+/Sn, which substance is the electrode that gains weight? A) Co C) Sn E) both Sn and Co B) Co2+ D) Sn2+ Br 2 ® 2 Br – + 2e – Br 2 + 2e – ® 2 Br – H 2 ® 2 H + + 2e – H2 + 2e – ® 2 H+ H2 + 2 H+ ® 2e – + 4 H 8. 3. For the following question refer to the table below. What electrode gains weight in the electrochemical cell? Fe/Fe 2+|| Ag+ /Ag What is the E° for the reaction: Hg ® Hg2+ + 2e –? A) +1.65 B) +0.85 C) –0.05 D) –0.85 E) –1.65 4. In the reaction Sn2+(aq) + 2 Ag + (aq) ® Sn4+(aq) + 2 Ag(s) What is the half–reaction equation for the oxidizing agent above? A) Sn2+ ® Sn4+ + 2e – C) Sn2+ + 2e – ® Sn4+ E) Sn2+ + Sn4+ ® 2e – B) Ag+ + e – ® Ag D) Ag+ ® Ag + e– 5. The function of the salt bridge in an electrochemical cell is to A) B) C) D) E) increase the cell voltage maintain electrical neutrality increase the oxidation–reduction rate supply a travel pathway for electrons increase the rate of attainment of equilibrium A) B) C) D) E) Ag Ag+ Fe Fe 2+ It cannot be determined from the information given 9. Which half-reaction would occur at the cathode of an electrochemical cell? A) B) C) D) E) Au ® Au3+ + 3e – Au + 3e– ® Au3+ Au3+ ® Au + 3e– Au 3+ + 3e – ® Au Au + Au 3+ ® 3e – + Au3+ 10. Which substance is the electrode that gains weight during the operation of this electrochemical cell? Cr/Cr 3+ || Pb 2+/Pb A) Cr C) Pb E) both Cr and Pb B) Cr 3+ D) Pb2+ A) Cl 2 B) Br 2 C) Hg2+ B) Br – C) Cr D) Cr 3+ E) Al D) I 2 Cu ®Cu2+ + 2e – E) I – 12. Which is the most easily oxidized? A) Cl – B) Br 2 15. What is the oxidation potential for the reaction? 11. Which is the most easily reduced? A) Cl 2 14. Which is the strongest reducing agent? C) Hg(l) D) I – 13. Which is the strongest oxidizing agent? A) -0.52 V C) +0.18 V E) +0.52 V B) -0.34 V D) +0.34 V 16. What is the standard reduction potential of Na if the standard hydrogen half-cell potential is changed from 0.00 to +0.40 volts? E) Br 2 A) -3.11 V C) -2.31 V E) +3.11 V B) -2.71 V D) 0.00 V 17. What is the electrode potential of the standard hydrogen half-cell reaction? A) HNO 3 C) Cu E) H+ B) Ag+ D) H2 A) -0.83 V C) +0.83 V E) +1.23 V B) 0.00 V D) +0.96 V 18. What is the standard electrode potential, E°, for this half-reaction? 2Ag+ + 2e – ® 2Ag 22. In an electrochemical cell, the positive ions go from the A) B) C) D) E) anode to the cathode through the wire cathode to the anode through the wire anode to the cathode through the salt bridge cathode to the anode through the salt bridge cathode to the anode through the wire and anode to the cathode through the salt bridge 23. In an electrochemical cell, the electrons go from the A) –0.80 V C) +0.40 V E) +1.60 V B) –1.60 V D) +0.80 V 19. For the following question refer to the table below. A) B) C) D) E) anode to the cathode through the wire cathode to the anode through the wire anode to the cathode through the salt bridge cathode to the anode through the salt bridge anode to the cathode through the wire and cathode to the anode through the salt bridge 24. Which is the cathode of this electrochemical cell? Cr + Au3+ ® Cr 3+ + Au What is the E° for this reaction? 2 Cr ® 2 Cr 3+ + 6e A) +1.48 V C) 0.00 V E) –1.48 V – B) +0.74 V D) –0.74 V 20. The negative ions go to which electrode in the voltaic cell Mg/Mg2+||Ag+ /Ag? A) Ag C) Mg E) both Ag and Mg B) Ag+ D) Mg 2+ 21. To which electrode do the electrons move in the cell A) B) C) D) E) Cr Au3+ Cr 3+ Au It cannot be determined unless the potentials are known 25. Base your answer on the table below. Zn/Zn2+||Pb 2+/Pb? A) B) C) D) E) Pb Pb2+ Zn Zn2+ It cannot be determined unless the potentials are known. Which is an oxidizing agent capable of converting Mg to Mg2+, but not Zn to Zn2+? A) Al 3+ C) Ba2+ E) None of the above B) Ba D) Mn 26. Base your answer on the table below. 29. Base your answer on the table below. Which statement is true? A) B) C) D) E) Fe 3+ reduces Fe2+ to Fe. Fe oxidizes Fe 2+ to Fe 3+. Fe reduces Fe 3+ to Fe 2+. Fe 3+ oxidizes Fe to Fe2+. Fe 2+ reduces Fe3+ to Fe. 27. Base your answer on the table below. Ions of the transition elements are generally colored. What color will the final solution be when a solution of Fe(NO 3) 2 is mixed with an acid solution of KMnO 4? A) clear C) purple E) brown 30. Base your answer on the table below. Which substance is most easily oxidized? A) Sn2+ B) Sn4+ C) Nb D) Nb3+ B) green D) yellow E) 2e – 28. Base your answer on the table below. Which statement is true? Which is an agent which oxidizes H 2 to H + , but not Hg to Hg2+? A) Br 2 B) Cl – C) Cu D) I 2 E) Mn 2+ A) Br 2 will oxidize the chloride ion, but not the iodide ion. B) Br2 will oxidize the iodide ion, but not the chloride ion. C) I 2 will oxidize the chloride ion, but not the bromide ion. D) I 2 will oxidize the chloride ion, but not the bromide ion. E) Cl 2 will oxidize the bromide ion, but not the iodide ion. 31. Base your answer on the table below. What is the net voltage of this electrochemical cell? Cr/Cr 3+ || Ni 2+/Ni A) 2.00 V C) 0.74 V E) –1.00 V B) 1.00 V D) 0.48 V 32. Base your answer on the table below. 34. Base your answer on the table below. Which statement is true? Bromide ion, Br –(aq), reduces A) B) C) D) E) I –(aq), but not fluorine, F 2(g). F2(g), but not chlorine, Cl 2(g). I 2(s), but not fluoride ion, F–(aq). Cl 2(g), but not fluoride ion, F –(aq). none of these other ions or gases. 35. Base your answer on the table below. What is the net potential developed by an electrochemical cell with these half reactions? A) +0.89 V C) +0.63 V E) –0.89 V B) +0.76 V D) –0.63 V 33. When magnesium metal is added to an unknown acid solution, a brownish colored gas is observed. What is most likely to be the unknown acid? Which will react with hydrochloric acid? A) Al and Ca C) Ca and Cu E) Ca only B) Al and Cu D) Cr and Cu A) B) C) D) E) Water Nitrous acid Hydrochloric acid Acid and permanganate ion Nitric acid 36. Base your answer on the table below. 39. Base your answer on the table below. Which statement is true? Which species will reduce Cu 2+ to Cu? A) Ag C) Cl – E) Sn2+ B) Au D) H+ + MnO4– 37. Base your answer on the table below. What is the initial net cell potential for the electrochemical cell, Ga/Ga 3+||Hg2+/Hg? A) –0.29 V C) 1.41 V E) 3.67 V B) 0.29 V D) 1.43 V A) B) C) D) E) Al 3+ will oxidize Cr but not Ca. Al 3+ will oxidize Ca but not Cr. Ca2+ will oxidize Cr but not Al. Ca2+ will oxidize Al but not Cr. Cr 3+ will oxidize Al but not Ca. 40. As the reaction in an electrochemical cell approaches equilibrium, the rate of the anode reaction A) B) C) D) E) decreases to zero decreases somewhat increases somewhat increases a large amount remains the same 41. What is the net potential (E°) for this reaction at equilibrium? 2 Fe 3+ + 2 I – «2 Fe 2+ + I 2 38. Base your answer on the table below. What is the net cell potential of the electrochemical cell Fe/Fe 2+||Cu 2+/Cu? A) +1.58 V C) +0.11 V E) –0.79 V B) +0.79 V D) –0.11 V A) 0.00 volts C) 1.00 volts E) 2.08 volts B) 0.23 volts D) 1.31 volts 42. In order for a redox reaction to be at equilibrium, the potential (E°) must be A) less than –1 C) 0 E) greater than 1 B) between 0 and –1 D) between 0 and 1 43. What is the potential (E°) of an electrochemical cell which has reached equilibrium? A) less than 0 C) between 0 and 1 E) greater than 1 B) 0 D) 1 44. As the reaction in an electrochemical cell approaches equilibrium, the voltage of the cell A) B) C) D) E) 49. Which substance is reduced? 5 HSO 3– + 2 IO3– ® 5 SO 42– + I 2 + 3 H+ + H2O increases decreases remains the same increases, then decreases decreases, then increases A) B) C) D) E) 45. For the following question refer to the table below. I2 IO3– SO 42– HSO 3– This is not a redox reaction 50. To electroplate copper on a carbon rod, the carbon rod must be A) B) C) D) E) What is the cell potential, Eº, at equilibrium for the cell: Pb/Pb 2+||Cu 2+/Cu? A) +0.47 B) +0.21 C) 0.00 D) –0.21 E) –0.47 the anode the cathode in acid solution in melted copper the positive electrode 51. 46. Which substance is oxidized? 2 Cr + 3 Pb(NO 3) 2 ® 2 Cr(NO 3) 2 + 3 Pb A) Cr C) Cr(NO 3) 2 E) NO 3– B) Pb D) Pb(NO 3) 2 47. What gas is released when a piece of zinc, Zn, is added to a hydrochloric acid solution, HCl(aq)? A) B) C) D) E) Chlorine, Cl 2 Hydrogen, H2 Zinc chloride, ZnCl 2 Hydrogen chloride, HCl Oxygen, O 2 48. Which substance is oxidized? Pb(NO 3) 2 ®PbO 2 + 2 NO 2 A) B) C) D) E) NO 2 PbO 2 Pb(NO 3) 2 NO 3– This is not a redox reaction Which is the strongest oxidizing agent? A) Sn4+(aq) C) Al 3+(aq) E) Sn(s) B) Sn2+(aq) D) Al(s) 52. Which is the reduced substance Mg(s) + 2 HCl(aq) ® MgCl 2(aq) + H 2(g) A) B) C) D) E) H2(g) HCl(aq) Mg(s) MgCl 2(aq) This is not a redox reaction 53. Which is the substance that is oxidized? 2 KI(aq) + Cl2(aq) ® 2 KCl(aq) + I2(aq) A) B) C) D) E) Cl 2 I2 KCl KI This is not a redox reaction 54. Which is the substance which is reduced? 59. Consider the unbalanced redox equation skeleton. SnCl 2(aq) + 2 FeCl3(aq) ® 2 FeCl 2(aq) + SnCl4(aq) A) B) C) D) E) FeCl 2(aq) FeCl3(aq) H2(g) SnCl 2(aq) This is not a redox reaction 55. Which substance is reduced? 2 Cr + 3 Pb(NO 3) 2 ®2 Cr(NO 3) 2 + 3 Pb A) Cr C) Cr(NO 3) 2 E) NO 3– B) Pb D) Pb(NO 3) 2 56. Which reaction is balanced? A) B) C) D) E) HBr + H 2SO 4 ® Br 2 + SO 2 + H2O 2 HBr + H2SO 4 ® Br2 + SO 2 + 2 H2O 2 HBr + 2 H 2SO 4 ® Br 2 + 2 SO 2 + 4 H2O 4 HBr + H 2SO 4 ® 2 Br 2 + SO 2 + 2 H2O 4 HBr + H 2SO 4 ® 2 Br 2 + SO 2 + 2 H2O + 8e– 57. Pb + Cr2O72– + H+ ® Pb2+ + Cr 3+ + H2O Which is the balanced overall reaction? A) B) C) D) Pb + Cr2O72– + H+ ® Pb2+ + Cr 3+ + H2O Pb + Cr2O72– + 14 H+ ® Pb2+ + 2Cr 3+ + 7 H2O Pb + Cr2O72– + H+ + 6e – ® Pb2+ + Cr 3+ + H2O 2 Pb + Cr2O72– + 14 H+ ® 2 Pb2+ + 2 Cr 3+ + 7 H2 O E) 3 Pb + Cr 2O 72– + 14 H+ ® 3 Pb2+ + 2 Cr3+ + 7 H 2O 60. Consider the unbalanced redox equation skeleton. Pb + Cr2O72– + H+ ® Pb2+ + Cr 3+ + H2O Which is the balanced reduction reaction? A) B) C) D) E) Pb ® Pb2+ + 2e – Pb2+ + 2e – ® Pb 2Cr 3+ + 7H2O ® Cr 2O72– + 14H+ + 6e – Cr2O 72– + 14H+ + 6e – ® 2Cr3+ + 7H2O Cr 2O72– + 6e – ® 2Cr 3+ + 7O2– 61. Consider the unbalanced redox equation skeleton. Pb + Cr2O72– + H+ ® Pb2+ + Cr 3+ + H2O Which is the balanced oxidation reaction? Which reaction is balanced? A) B) C) D) Cu + MnO 4– + H+ ® Cu2+ + Mn 2+ + H2O Cu + MnO 4– + 8 H+ ® Cu2+ + Mn 2+ + 4 H2O 5Cu + MnO 4– + 8 H+ ® 5 Cu2+ + Mn 2+ + 4 H2O 5Cu + 2 MnO 4– + 16 H+ ® 5 Cu 2+ + 2 Mn 2+ + 8 H2O E) 5Cu + 2 MnO 4– + 16 H+ ® 5 Cu2+ + 2 Mn 2+ + 8 H2O + 10e– 58. Which is correctly balanced? A) B) C) D) E) Ag + 2 HNO 3 ® AgNO3 + NO + H2O Ag + 4 HNO 3 ® AgNO3 + 7 NO + 2H2O 3 Ag + 4 HNO 3 ® 3 AgNO3 + NO + 2 H2O Ag + 2 HNO 3 ® AgNO3 + NO + 2 H2O 3 Ag + 4 HNO 3 ® 3 AgNO3 + NO + 2 H2O + 3e– A) B) C) D) E) Pb ® Pb2+ + 2e – Pb2+ + 2e – ® Pb 2Cr 3+ + 7H2O ® Cr 2O72– + 14H+ + 6e – Cr 2O72– + 14H+ + 6e – ® 2Cr 3+ + 7H2O Cr 2O72– + 6e – ® 2Cr 3+ + 7O2– 62. What is the coefficient of phosphorus, P, when the equation is balanced using small whole numbers? H2SO 4 + P ® H3PO 4 + H2O + SO 2 A) 1 B) 2 C) 10 D) 4 E) 5 63. How many moles of zinc, Zn, will reduce one mole of vanadium from V5+ to V 2+? The unbalanced expression is V5+(aq) + Zn(s) ® V2+(aq) + Zn 2+(aq) A) 1 1/ 2 B) 2 C) 2 1/ 2 D) 2/ 5 E) 4/ 5 64. Which substance is reduced? 2 NaOH + H 2SO 4 ®Na2SO 4 + 2 H2O A) B) C) D) E) H2O NaOH H2SO 4 Na2SO 4 This is not a redox reaction 65. Which substance is oxidized? 2 NaOH + H 2SO 4 ®Na2SO 4 + 2 H2O A) B) C) D) E) H2O NaOH H2SO 4 Na2SO 4 This is not a redox reaction 66. Which is a redox reaction? A) B) C) D) E) 68. A 1.0 M solution of ZnCl 2 is electrolyzed. Which are the correct half–reactions? BaSO 4 ® Ba2+ + SO 42– Cu(NO 3) 2 + H2S ® CuS + 2 HNO 3 CaCO 3 ® CaO + CO 2 2 Al + 6 H2O ® 2 Al(OH) 3 + 3 H2 NH 4+ ® H+ + NH 3 67. A 1.0 M solution of NiBr2 is electrolyzed. Which are the correct half–reactions? A) Anode: Br 2 + 2e – ® 2 Br – Cathode: Ni ® Ni 2+ + 2e – B) Anode: 2 Br – ® Br 2 + 2e – Cathode: 2 H 2O + 2e – ® H 2 + 2 OH – C) Anode: 2 H2O ® O2 + 4 H+ + 4e – Cathode: 2 Ni 2+ + 4e – ® 2 Ni D) Anode: 2 H2O ® O2 + 4 H+ + 4e – Cathode: 4 H 2 O + 4e – ® 2 H 2 + 4 OH – E) Anode: 2 Br – ® Br2 + 2e – Cathode: Ni 2+ + 2e – ® Ni A) Anode: 2 Cl – ® Cl 2 + 2e – Cathode: Zn 2+ + 2e – ® Zn B) Anode: 2 Cl – ® Cl 2 + 2e – Cathode: 2 H 2O + 2e – ® H 2 + 2 OH – C) Anode: 2 H 2O ® O 2 + 4 H+ + 4e – Cathode: 2 Zn2+ + 4e – ® 2 Zn D) Anode: 2 H2O ® O2 + 4 H+ + 4e – Cathode: 4 H 2 O + 4e – ® 2 H 2 + 4 OH – E) Anode: Cl 2 + 2e – ® 2 Cl – Cathode: Zn ® Zn 2+ + 2e – 69. What are the anode and cathode half–reactions for the electrolysis of fused (melted) NaCl? A) Anode: 2 Cl– ® Cl 2 + 2e – Cathode: 2 Na+ + 2e – ® 2 Na B) Anode: 2 Cl – ® Cl 2 + 2e – Cathode: 2 H 2O + 2e – ® H 2 + 2 OH – C) Anode: 2 H2O ® O2 + 4 H+ + 4e – Cathode: 4 Na+ + 4e – ® 4 Na D) Anode: 2 H2O ® O2 + 4 H+ + 4e – Cathode: 4 H 2 O + 4e – ® 2 H 2 + 4 OH – E) Anode: Cl 2 + 2e – ® 2 Cl – Cathode: 2 Na ® 2 Na+ + 2e – 70. What are the anode and cathode reactions during the electrolysis of fused KBr? – A) Anode: 2 H2O ® O2 + 4 H+ + 4e Cathode: 4 K+ + 4e – ® 4 K B) Anode: 2 Br – ® Br 2 + 2e – Cathode: 2 H 2O + 2e – ® H2 + 2 OH – C) Anode: Br 2 + 2e – ® 2 Br – Cathode: 2 K ® 2 K+ + 2e – D) Anode: 2 H2O ® O2 + 4 H+ + 4e – Cathode: 4 H 2 O + 4e – ® 2 H 2 + 4 OH – E) Anode: 2 Br – ® Br2 + 2e – Cathode: 2 K + + 2e –® 2K 71. An electrolytic cell differs from a chemical (or voltaic) cell in that the electrolytic cell A) B) C) D) E) is exothermic produces an electric current uses an applied electric current involves oxidation and reduction reactions occurs spontaneously 72. One mole of electrons is passed through aqueous systems containing the stated ion and two inert electrodes. Which will have the greatest mass of deposited element? A) C) E) 56Fe 3+ 112Cd 2+ B) D) 108Ag + Mg 2+(aq) + 2 Cl–(aq) ® Mg(s) + Cl 2(l) How many grams of magnesium metal are produced by the electrolysis of 0.10 mole of melted magnesium chloride, MgCl2 ? C) 2.4 D) 4.8 E) 12 74. What is the charge and the reaction occurring at the anode of an electrolysis reaction? A) B) C) D) E) (+), oxidation (+), reduction (–), reduction (–), oxidation reactions only occur at the cathode 75. In the electrolysis of molten CaCl 2 , the species oxidized is A) B) C) D) E) Ca Ca2+ Cl – Cl 2 Oxidation does not occur 76. In the electrolysis of aqueous copper (II) bromide solution, CuBr 2(aq), 1.00 gram of Cu is deposited at the cathode. How many grams of bromine are formed at the anode? A) 2.00 grams C) 3.00 grams E) 159 grams B) 2.52 grams D) 79.9 grams B) at the anode D) at the salt bridge 78. At the cathode during electrolysis, what is its charge and what type of reaction occurs. A) B) C) D) E) (–), oxidation (+), oxidation (–), reduction (+), reduction no reaction occurs at the cathode A) at the wire C) at the cathode E) in solution 73. Given the equation: B) 0.24 A) in the wire C) at the cathode E) in solution 79. Electroplating occurs during electrolysis 197Au 3+ 207Pb2+ A) 0.12 77. Electroplating always takes place B) at the anode D) at the salt bridge 80. The mass of a metal deposited at the cathode during electroplating is proportional to the A) B) C) D) radius of the cation activity of the metal temperature of the electrolyte quantity of electrical charge passed through the cell E) molarity of the ions in solution 81. If fused silver chloride, AgCl, is electrolyzed, the Ag+ ions are A) B) C) D) E) reduced at the negative electrode reduced at the positive electrode oxidized at the negative electrode oxidized at the positive electrode neither oxidized nor reduced 82. From which aqueous system will one mole of electrons deposit the greatest mass of the element ? A) C) E) 207Pb2+ 59Ni 2+ B) D) 108Ag + 56Fe 2+ 27Al 3+ 83. How many grams of copper metal are deposited from a solution of copper (II) sulfate, CuSO 4 , by 0.500 mole of electrons? A) 15.9 g C) 47.7 g E) 127 g B) 31.8 g D) 63.5 g Answer Key AP Chemistry Electrochemistry Review 1. C 37. C 73. C 2. C 38. B 74. A 3. D 39. B 75. C 4. B 40. B 76. B 5. B 41. A 77. C 6. D 42. C 78. C 7. C 43. B 79. C 8. A 44. B 80. D 9. D 45. C 81. A 10. C 46. A 82. B 11. A 47. B 83. A 12. D 48. C 13. A 49. B 14. E 50. B 15. B 51. A 16. C 52. B 17. B 53. D 18. D 54. B 19. B 55. D 20. C 56. B 21. A 57. D 22. C 58. C 23. A 59. E 24. D 60. D 25. A 61. A 26. C 62. B 27. C 63. A 28. D 64. E 29. D 65. E 30. B 66. D 31. D 67. E 32. C 68. C 33. A 69. A 34. D 70. E 35. E 71. C 36. E 72. B