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Name: ______________________ Class: _________________ Date: _________ Chpt 20/21 review Multiple Choice Identify the choice that best completes the statement or answers the question. ____ 1. If an atom is reduced in a redox reaction, what must happen to another atom in the system? a. It must be oxidized. b. It must be reduced. c. It must be neutralized. d. Nothing needs to happen to another atom in the system. ____ 2. Which of these metals tends to resist losing electrons to corrosion? a. aluminum b. iron c. platinum d. zinc ____ 3. In which of the following types of reaction are electrons gained? a. decomposition b. oxidation c. neutralization d. reduction ____ 4. What particles are transferred in an oxidation-reduction reaction? a. protons b. ions c. electrons d. atoms ____ 5. How does a block of zinc attached to a steel ship hull protect the hull from corrosion? a. Zinc is a better reducing agent so it corrodes instead of the iron corroding. b. Zinc is a better oxidizing agent so it corrodes instead of the iron corroding. c. The zinc carries electrons toward the iron so that the iron cannot react. d. The zinc carries electrons away from the iron so that the iron cannot react. ____ 6. Cu → Cu + 2 eThe equation above represents a reaction that can be classified as ____. a. redox b. hydrolysis c. reduction d. oxidation ____ 7. Which type of reaction does Sn a. oxidation b. reduction c. hydrolysis d. redox 2+ 2+ → Sn 4+ represent? 1 ID: A Name: ______________________ ____ ____ ID: A 8. What is the reducing agent in the following reaction? 2Na + 2H 2 O → 2NaOH + H 2 a. b. Na H2 O c. d. NaOH H2 9. What process occurs during the corrosion of iron? a. Iron is oxidized. b. Iron is reduced. c. Iron (III) is oxidized. d. Iron (III) is reduced. ____ 10. Why is oxygen reduced in the reaction of hydrogen with oxygen to make water? a. Oxygen pulls electrons toward itself. b. Oxygen pushes electrons toward the hydrogens. c. Oxygen absorbs a proton. d. Oxygen releases a proton. ____ 11. The a. b. c. d. oxidation number of magnesium in magnesium chloride is ____. –1 0 +1 +2 ____ 12. The a. b. c. d. oxidation number of bromine in bromine gas is ____. +1 –1 0 –2 ____ 13. In which of the following species is the oxidation number of sulfur less than 6? a. SO 3 b. Na 2 SO 4 c. SO 4 d. S2 O 4 2− 2− ____ 14. In the following unbalanced reaction, which atom is reduced? H 2 O + Cl 2 + SO 2 → HCl + H 2 SO 4 a. b. c. d. hydrogen oxygen chlorine sulfur 2 Name: ______________________ ID: A ____ 15. In the following unbalanced reaction, which atom is oxidized? HNO 3 + HBr → NO + Br 2 + H 2 O a. b. c. d. hydrogen nitrogen oxygen bromine ____ 16. Which of the following chemical equations represents an oxidation-reduction reaction? a. Mg(OH) 2 + 2HCl → MgCl 2 + 2H2 O b. BiCl 2 + Na 2 SO 4 → 2NaCl + BiSO 4 c. CH4 + 2O2 → CO 2 + 2H2 O d. 3NaOH + H 3 PO 4 → Na 3 PO 4 + 3H 2 O ____ 17. Which element increases its oxidation number in the following reaction? 3KOH + H 3 PO 4 → K 3 PO 4 + 3H 2 O a. b. c. d. oxygen potassium phosphorus no changes in oxidation number ____ 18. The oxidation number of what atom or ion decreases in the following reaction? I 2 + 2KCl → 2KI + Cl 2 a. b. c. d. iodine atom potassium atom chlorine ion potassium ion ____ 19. Which of the following chemical equations represents a redox reaction? a. 2Na + 2H2 O → 2NaOH + H2 b. HCl + KOH → KCl + H2 O c. AgNO3 (aq) + NaCl(aq) → ΝaNO3 (aq) + AgCl(s) + H2 O(l) d. Fe3+ + 3NO3 – + 3Na+ + 3OH– → Fe(OH)3 + 3Na+ + 3NO3 – + ____ 20. What is the coefficient for H when this half-reaction is balanced? + 2+ H + MnO 2 → Mn + H 2 O a. b. c. d. 1 2 3 4 3 Name: ______________________ ID: A ____ 21. What is the reduction half-reaction for the following unbalanced redox equation? 2− + Cr 2 O 7 + NH 4 → Cr 2 O 3 + N 2 a. Cr 2 O 3 → Cr 2 O 7 b. Cr 2 O 7 c. NH d. N 2 → NH 4 + 4 2− 2− → Cr 2 O 3 → N2 + ____ 22. What is the key factor in defining a reaction as an oxidation-reduction reaction? a. transfer of electrons between atoms b. oxygen as one of the reactants c. making and breaking ionic bonds d. precipitation of solid from the reaction solution ____ 23. The a. b. c. d. half-reaction method is particularly useful for balancing which type of equation? dissociation acid-base redox combustion ____ 24. Which term describes the following process? 2Fe(s) + O 2 (g) + 2H 2 O(l) → 2Fe(OH) 2 (s) 4Fe(OH) 2 (s) + O 2 (g) +2H 2 O(l) → 4Fe(OH) 3 (s) a. b. c. d. salt hydrolysis electrolysis corrosion buffering ____ 25. Which of the following is an oxidation half-reaction? 2+ 4+ a. Sn → Sn + 2e − b. Cl 2 + 2e − → 2Cl − + c. O 2 + 4H + 4e − → 2H 2 O d. Fe 3+ + e − → Fe 2+ ____ 26. Which of these metal’s ions are most easily reduced ? a. iron b. mercury c. aluminum d. potassium ____ 27. How is the cell potential of a voltaic cell calculated? a. Ecell = Ered − Eoxid b. Ecell = Eoxid − Ered c. Ecell = Ered + Eoxid d. Ecell = Ered ÷ Eoxid 4 Name: ______________________ ID: A 2+ ____ 28. In a zinc-copper cell, Zn | Zn (1M) || Cu 2+ a. Cu (aq) b. Cu(s) c. Zn(s) 2+ d. Zn (aq) 2+ (1M) | Cu, of which material is the negative made? ____ 29. How can a redox reaction be used as a source of electrical energy? a. Two half-reactions must be physically separated. b. One half-reaction must involve two metals. c. Two half-reactions must involve more than one electron. d. One half-reaction must use a metal wire electrode. ____ 30. Which electrode is labeled as positive in a voltaic cell? a. anode b. cathode c. standard hydrogen electrode d. mercury electrode ____ 31. →The half reaction at a barium electrode is: Ba2+ + 2e − → Ba For a cell using a barium electrode and a hydrogen electrode, E° = 2.90 V. What is the standard reduction potential of the barium electrode? a. b. c. d. −2.90 V −1.45 V 1.45 V 2.90 V ____ 32. Which of the following factors does NOT affect the voltage produced in a voltaic cell? a. metal of the electrodes b. concentrations of ions c. temperature d. pressure ____ 33. What is the electrode in the center of the most common dry cell made of? a. copper b. zinc c. iron d. graphite ____ 34. What is oxidized in a graphite dry cell battery? a. copper b. zinc c. iron d. carbon ____ 35. What is reduced in a graphite dry cell battery? a. copper b. zinc c. manganese dioxide d. carbon 5 Name: ______________________ ID: A ____ 36. Why can’t a lead storage battery be recharged indefinitely? a. A direct current must pass through the cells. b. The electrodes lose lead sulfate. c. It is difficult to reverse the direction of current flow. d. The electrolyte is too expensive. ____ 37. The a. b. c. d. substance reduced in a hydrogen-oxygen fuel cell is ____. water hydrogen hydrogen peroxide oxygen ____ 38. What causes current to flow in an electrolytic cell? a. an outside power source b. a spontaneous redox reaction c. a nonspontaneous redox reaction d. difference in potential between the two half-cells ____ 39. By a. b. c. d. convention, which electrodes are labeled as the positive electrodes in electrochemical cells? cathode in electrolytic cells, anode in voltaic cells anode in electrolytic cells, cathode in voltaic cells cathode in both types of cells anode in both types of cells ____ 40. What is the purpose of the electrolyte in a cell used to electrolyze water? a. It reacts with water to produce hydrogen. b. It reacts with water to produce oxygen. c. It carries current between the electrodes. d. It neutralizes the ions produced at the electrodes. ____ 41. What is produced in the electrolysis of brine? a. chlorine gas, sodium hydroxide, and hydrogen gas b. chlorine gas and hydrogen gas only c. chlorine gas and oxygen gas only d. chlorine gas and sodium only 6 ID: A Chpt 20/21 review Answer Section MULTIPLE CHOICE 1. ANS: A PTS: 1 DIF: L1 REF: p. 693 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: knowledge 2. ANS: C PTS: 1 DIF: L1 REF: p. 697 OBJ: 20.1.2 Explain how the presence of salts and acids accelerates the corrosion of metals. BLM: comprehension 3. ANS: D PTS: 1 DIF: L1 REF: p. 694 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: knowledge 4. ANS: C PTS: 1 DIF: L1 REF: p. 694 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: knowledge 5. ANS: A PTS: 1 DIF: L2 REF: p. 698 OBJ: 20.1.2 Explain how the presence of salts and acids accelerates the corrosion of metals. BLM: comprehension 6. ANS: D PTS: 1 DIF: L2 REF: p. 694 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: application 7. ANS: A PTS: 1 DIF: L2 REF: p. 694 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: application 8. ANS: A PTS: 1 DIF: L2 REF: p. 695 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: application 9. ANS: A PTS: 1 DIF: L2 REF: p. 697 OBJ: 20.1.2 Explain how the presence of salts and acids accelerates the corrosion of metals. BLM: comprehension 10. ANS: A PTS: 1 DIF: L2 REF: p. 696 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: comprehension 11. ANS: D PTS: 1 DIF: L2 REF: p. 702 OBJ: 20.2.1 State the general rule for assigning oxidation numbers. BLM: analysis 12. ANS: C PTS: 1 DIF: L2 REF: p. 702 OBJ: 20.2.1 State the general rule for assigning oxidation numbers. BLM: comprehension 13. ANS: D PTS: 1 DIF: L2 REF: p. 702 | p. 703 OBJ: 20.2.1 State the general rule for assigning oxidation numbers. BLM: analysis 14. ANS: C PTS: 1 DIF: L2 REF: p. 706 OBJ: 20.2.2 Define oxidation and reduction in terms of a change in oxidation number. BLM: application 1 ID: A 15. ANS: D PTS: 1 DIF: L2 REF: p. 706 OBJ: 20.2.2 Define oxidation and reduction in terms of a change in oxidation number. BLM: analysis 16. ANS: C PTS: 1 DIF: L2 REF: p. 707 OBJ: 20.3.1 Identify the two classes of chemical reactions. BLM: analysis 17. ANS: D PTS: 1 DIF: L2 REF: p. 701 OBJ: 20.2.2 Define oxidation and reduction in terms of a change in oxidation number. BLM: analysis 18. ANS: A PTS: 1 DIF: L2 REF: p. 706 OBJ: 20.2.2 Define oxidation and reduction in terms of a change in oxidation number. BLM: analysis 19. ANS: A PTS: 1 DIF: L2 REF: p. 709 OBJ: 20.3.1 Identify the two classes of chemical reactions. BLM: application 20. ANS: D PTS: 1 DIF: L2 REF: p. 712 OBJ: 20.3.2 Balance a redox equation using the oxidation-number-change method. BLM: analysis 21. ANS: B PTS: 1 DIF: L2 REF: p. 712 OBJ: 20.3.2 Balance a redox equation using the oxidation-number-change method. BLM: application 22. ANS: A PTS: 1 DIF: L1 REF: p. 692 OBJ: 20.1.1 Describe what happens to a substance that undergoes oxidation and a substance that undergoes reduction. BLM: knowledge 23. ANS: C PTS: 1 DIF: L2 REF: p. 712 OBJ: 20.3.2 Balance a redox equation using the oxidation-number-change method. BLM: comprehension 24. ANS: C PTS: 1 DIF: L2 REF: p. 697 OBJ: 20.1.2 Explain how the presence of salts and acids accelerates the corrosion of metals. BLM: comprehension 25. ANS: A PTS: 1 DIF: L2 REF: p. 712 OBJ: 20.3.2 Balance a redox equation using the oxidation-number-change method. BLM: comprehension 26. ANS: B PTS: 1 DIF: L2 REF: p. 729 OBJ: 21.1.1 Identify the type of chemical reaction involved in all electrochemical processes. BLM: comprehension 27. ANS: A PTS: 1 DIF: L2 REF: p. 737 OBJ: 21.2.1 Identify what causes the electrical potential of an electrochemical cell. BLM: comprehension 28. ANS: C PTS: 1 DIF: L2 REF: p. 731 OBJ: 21.1.2 Describe how a voltaic cell produces electrical energy. BLM: comprehension 29. ANS: A PTS: 1 DIF: L1 REF: p. 730 OBJ: 21.1.2 Describe how a voltaic cell produces electrical energy. BLM: knowledge 30. ANS: B PTS: 1 DIF: L1 REF: p. 730 OBJ: 21.1.2 Describe how a voltaic cell produces electrical energy. BLM: knowledge 2 ID: A 31. ANS: A PTS: 1 DIF: L2 REF: p. 739 OBJ: 21.2.2 Determine the standard reduction potential of a half-cell. BLM: application 32. ANS: D PTS: 1 DIF: L2 REF: p. 737 OBJ: 21.2.1 Identify what causes the electrical potential of an electrochemical cell. BLM: comprehension 33. ANS: D PTS: 1 DIF: L1 REF: p. 733 OBJ: 21.1.3 Identify the current applications that use electrochemical processes to produce energy. BLM: knowledge 34. ANS: B PTS: 1 DIF: L1 REF: p. 732 OBJ: 21.1.3 Identify the current applications that use electrochemical processes to produce energy. BLM: knowledge 35. ANS: C PTS: 1 DIF: L1 REF: p. 732 OBJ: 21.1.3 Identify the current applications that use electrochemical processes to produce energy. BLM: knowledge 36. ANS: B PTS: 1 DIF: L1 REF: p. 734 OBJ: 21.1.3 Identify the current applications that use electrochemical processes to produce energy. BLM: knowledge 37. ANS: D PTS: 1 DIF: L2 REF: p. 735 OBJ: 21.1.3 Identify the current applications that use electrochemical processes to produce energy. BLM: comprehension 38. ANS: A PTS: 1 DIF: L1 REF: p. 746 OBJ: 21.3.1 Distinguish between electrolytic and voltaic cells. BLM: knowledge 39. ANS: B PTS: 1 DIF: L1 REF: p. 746 OBJ: 21.3.1 Distinguish between electrolytic and voltaic cells. BLM: knowledge 40. ANS: C PTS: 1 DIF: L2 REF: p. 747 OBJ: 21.3.2 Describe some applications that use electrolytic cells. BLM: comprehension 41. ANS: A PTS: 1 DIF: L2 REF: p. 748 OBJ: 21.3.2 Describe some applications that use electrolytic cells. BLM: comprehension 3 electrical electrical electrical electrical electrical