SCHOOL YEAR 2017-18 NAME: CH- 19 OXIDATION-REDUCTION REACTIONS SUBJECT: CHEMISTRY GRADE: 12 TEST A Choose the best answer from the options that follow each question. 1. During oxidation, one or more electrons are removed from a substance, which increases its a. size. b. mass. c. valence. d. oxidation number. 2. The oxidation number of fluorine in a compound is always a. 0. b. 1. c. +1. d. +2. 3. In the reaction Cu + NO + H 3 O + Cu 2+ + NO + H 2 O, the coefficients of the balanced equation are a. 1, 2, 2, 1, 1, 1. b. 4, 3, 2, 4, 3, 1. c. 6, 1, 2, 6, 1, 1. d. 3, 2, 8, 3, 2, 12. 4. During a redox reaction, the oxidation numbers of oxidizing agents a. decrease. b. increase. c. remain the same. d. triple. 5. In the process of reduction, a. electrons are lost. b. electrons are gained. c. protons are gained. d. protons are lost. 6. The first step in the general plan for balancing redox equations is a. writing the half-reaction for reduction. b. writing the half-reaction for oxidation. c. writing the unbalanced formula equation.
d. adjusting the coefficients of half-reactions. 7. In the general plan for balancing redox equations, once a half-reaction has been written, to balance oxygen, a. water is added. b. oxygen gas is added. c. oxide ions are added. d. None of the above 8. In the general plan for balancing redox equations, once a half-reaction has been written, to balance charge, a. subscripts are adjusted. b. coefficients are adjusted. c. electrons are added to the side having the greater negative net charge. d. electrons are added to the side having the greater positive net charge. 9. In the general plan for balancing redox equations, when a reaction takes place in basic solution, you will need to add a. H + ions. b. H 3 O + ions. c. OH ions. d. O 2 ions. 10. In the general plan for balancing redox equations, once both half-reactions have been written and balanced, a. combine the half-reactions. b. cancel out anything common to both sides of the half-reactions. c. add electrons as necessary. d. Both (a) and (b) 11. What is the oxidation number of Mn in MnO? a. +4 b. +5 c. +6 d. +7 12. What is the oxidation number Cr in Cr 2 O? a. +4 b. +5 c. +6 d. +7 13. Which is the balanced equation for the oxidation of elemental magnesium by reaction with oxygen gas? a. Mg + O 2 Mg 2+ + 2O 2 b. Mg + O 2 Mg 2+ + 2O 2 + 4e c. Mg + O 2 + 4e Mg 2+ + 2O 2 d. Mg + O 2 2Mg 2+ + 2O 2 14. What is the balanced equation for the conversion of hydrogen peroxide to water? a. H 2 O 2 H 2 O + O 2 b. 2H 2 O 2 2H 2 O + O 2 c. 4H 2 O 2 4H 2 O + O 2 d. 8H + + 3O 4H 2 O + O 2
15. After the equation below has been balanced for a reaction in an acidic solution, what will the coefficients of the reactants and products be, in order? a. 1, 3, 1, 3 b. 2, 1, 2, 1 c. 2, 3, 2, 3 d. 1, 2, 2, 1 Fe + SnCl 4 FeCl 3 SnCl 2 16. After the equation below has been balanced for a reaction in an acidic solution, what will the coefficients of the reactants and products be, in order? a. 1, 2, 1, 1, 2 b. 2, 2, 2, 2, 2 c. 2, 1, 2, 2, 1 d. 1, 2, 1, 1, 1 H 2 O 2 + FeSO 4 + H 2 SO 4 Fe 2 (SO 4 ) 3 + H 2 O 17. After the equation below has been balanced for a reaction in an acid environment, what will the coefficients of the reactants and products be, in order? a. 3, 5, 3, 1, 3, 4 b. 1, 3, 1, 1, 1, 4 c. 3, 8, 3, 2, 3, 4 d. 2, 1, 2, 2, 1, 2 CuS + HNO 3 Cu(NO 3 ) 2 + NO + S + H 2 O 18. After the equation below has been balanced for a reaction in a basic environment, what will the coefficients of the reactants and products be, in order? Bi(OH) 3 + K 2 SnO 2 Bi + K 2 SnO 3 + H 2 O a. 1, 2, 1, 2, 1 b. 2, 3, 2, 3, 3 c. 2, 2, 2, 2, 2 d. 2, 1, 2, 1, 2 19. In the reaction represented by the equation 2NaOH + 6H 2 O + 2Al a. oxidized. b. reduced. c. neutralized. d. ionized. 2NaAl(OH) 4 + 3H 2, the Al is 20. In the reaction represented by the equation 6Br 2 + 6Ca(OH) 2 a. oxidizing agent. b. reducing agent. c. neutralized substance. d. Both (a) and (b) 5CaBr 2 + Ca(BrO 3 ) 2 + 6H 2 O, the Br 2 is the 21. An ion or element disproportionates if it a. loses electrons. b. gains electrons. c. becomes positively charged. d. Both (a) and (b) 22. All redox reactions involve the transfer of
a. protons. b. water. c. electrons. d. acids. 23. Reduction must always accompany oxidation because a. energy must be conserved. b. mass must be conserved. c. electrons must be conserved. d. a source of protons is required. 24. When a copper penny is placed into a solution of silver nitrate, AgNO 3, the copper forms copper(ii) nitrate, Cu(NO 3 ) 2, through the process of a. reduction. b. oxidation. c. disproportionation. d. dissolution. 25. What is the half-reaction of Zn in the reaction Zn(s) + HgO a. Zn(s) Zn +1 b. Zn(s) Zn +2 + 2e c. Zn(s) Zn +1 + 2e d. Zn(s) Zn +2 + 1e ZnO + Hg(s)?
TEST B PART I Choose the best answer from the options that follow each question. 1. In the reaction 2K + Br 2 2K + + 2Br, which species is reduced? a. K only b. Br 2 only c. Both K and Br 2 d. Neither K nor Br 2 2. Which of the following is an example of disproportionation? a. 2H 2 O 2 2H 2 O + O 2 b. 2H 2 O H 3 O + + OH c. Cu + 2AgNO 3 Cu(NO 3 ) 2 + 2Ag d. 2Li + 2H 2 O 2LiOH + H 2 3. In the silver half-reaction Ag 2 + 2e Ag(s), silver ions change into silver solid because they are a. oxidized. b. reduced. c. ionized. d. disintegrated. 4. In the oxidation-reduction reaction H 2 O +2MnO 2 + Zn Mn 2 O 3 + Zn(OH) 2, the half-reaction of the zinc is a. Zn(OH) 2 Zn + 2e. b. Zn(OH) 2 Zn + 2OH. c. Zn + 2OH Zn(OH) 2 + 2e. d. Zn + 2OH + 2e Zn(OH) 2. 5. Consider the two half-reactions below. I. Pb + HSO PbSO 4 II. PbO 2 + HSO PbSO 4 + 2H 2 O The reactant lead, Pb, is a. oxidized in both. b. reduced in both. c. disproportionated in both. d. oxidized in I and reduced in II. 6. In the reaction Zn + CuSO 4 Cu + ZnSO 4, a. Cu is oxidized and Zn 2+ is reduced. b. Cu is reduced and Zn 2+ is oxidized. c. Cu 2+ is oxidized and Zn is reduced. d. Cu 2+ is reduced and Zn is oxidized. 7. During redox reactions, reducing agents a. attain a more negative oxidation state. b. attain a more positive oxidation state. c. keep the same oxidation state. d. are not present. 8. The stronger oxidizing agent of two elements will usually be
a. oxidized. b. reduced. c. absorbed. d. disproportionated. 9. In a reduction reaction, the oxidation number becomes more negative due to a. loss of electrons. b. gain of electrons. c. disproportionation. d. addition of OH ions. 10. When a metal is separated from oxygen, the reaction leaves a much smaller amount of pure metal. The impure metal is said to have been a. reduced. b. oxidized. c. deoxygenated. d. ionized. 11. The elements in Groups 1 and 2 on the periodic table have oxidation numbers of a. +1, +3, respectively. b. +1, +2, respectively. c. +1, +3, respectively. d. +2, +3, respectively. 12. The oxidation number of H in LiH is a. +1 b. +2 c. 2 d. 1 13. The reaction Mg(s) + 2Ag + (aq) Mg 2+ (aq) + 2Ag(s) will occur because Mg(s) is a. a stronger oxidizing agent than Ag(s). b. a stronger reducing agent than Ag(s). c. reduced. d. disproportionated. 14. The half-reaction 2MnO 2 + H 2 O + 2e a. electrons. b. OH ions. c. Mn 2+ ions. d. O 2 ions. Mn 2 O 3 is missing 15. A metal that is more active than another metal is said to be a. a better oxidizing agent. b. a better reducing agent. c. a better redox substance. d. a disproportionated substance. 16. After the equation below has been balanced, what will the coefficients of the reactants and products be, in order? Fe 2+ (aq) + MnO 4 (aq) + H(aq) Fe 3+ (aq) + Mn 2+ (aq) + H 2 O(l) a. 5, 1, 7, 5, 1, 4
b. 5, 1, 8, 5, 1, 4 c. 1, 1, 2, 1, 1, 4 d. 1, 1, 4, 1, 1, 2 17. The oxidation number of S in SO 4 is a. 2. b. +2. c. +4. d. +6. 18. Restoration of old, darkened paintings often involves oxidation with H 2 O 2, as given by the following reaction: PbS (black) + 4H 2 O 2 Which is oxidized in this reaction? a. Pb b. S c. H d. O 19. Which is not an oxidizing agent? a. H 2 O 2 b. Cl 2 c. KMnO 4 d. Zn PbSO 4 (white) + 4H 2 O 20. Bleach (5.25% NaClO) is a good oxidizing agent because the oxidation state of Cl in ClO changes from +1 to a. 1. b. +2. c. +3. d. +4. 21. The equation representing the oxidation-reduction reaction of a piece of magnesium ribbon and hydrochloric acid is a. Mg(s) + HCl(aq) MgCl(aq) + H + (aq). b. Mg(s) + HCl(aq) MgCl 2 (aq) + H 2 (g). c. Mg(s) + HCl(aq) MgCl 2 (aq) + H + (aq). d. Mg + (aq) + HCl(aq) MgCl(aq) + H + (aq). 22. An iron nail is dropped into copper sulfate, and the nail becomes coated with copper. The equation representing the redox reaction is a. Fe(s) + Cu(s) CuSO 4 + FeSO 4. b. FeSO 4 + Cu(s) Fe + CuSO 4. c. Fe(s) + CuSO 4 FeSO 4 + Cu(s). d. Fe(s) + FeSO 4 Cu(s) + CuSO 4. 23. Since zinc is a stronger reducing agent than copper, the zinc is a. oxidized. b. reduced. c. ionized. d. disproportionated.
PART II Write the correct term (or terms) in the space provided. 24. The oxidation number of nitrogen in NO 2 is. 25. When hydrogen peroxide decomposes naturally, the products are and. 26. A process in which a substance acts as both an oxidizing agent and a reducing agent is called. 27. An oxidizing agent is the substance that is. 28. The oxidation number of oxygen in hydrogen peroxide is. In the space provided, label each of the following half-reactions as an oxidation half-reaction or a reduction half-reaction. 29. Br 2 + 2e 2Br 30. Fe 2+ + 2e Fe 31. Fe 2+ Fe 3+ + e In the space provided, write the oxidation numbers for each atom in the following compounds. 32. CaCO 3 33. Fe(NO 3 ) 2 34. 2KNO 3 (s) 2KNO 2 (s) + O 2 (g) 35. SO 2 (g) + H 2 O(l) H 2 SO 3 (aq) 36. H 2 (g) + CuO(s) Cu(s) + H 2 O(l) 37. Write the redox half-reaction for zinc solid forming zinc ions, Zn 2+ (aq). 38. Write the redox half-reaction of chlorine gas forming chlorine ions, Cl (aq). 39. Write the complete balanced zinc-chlorine gas redox reaction forming solid zinc chloride. 40. Balance the equation: K 2 Cr 2 O 7 + HCl KCl + CrCl 3 + H 2 O + Cl 2 Choose the best answer from the options that follow each question. 41. The oxidation number of oxygen atoms in compounds is usually a. 0. b. -1.
c. -2. d. +1 42. The part of a reaction that involves only oxidation or reduction is a(n) a. redox reaction. b. reduction reaction. c. oxidation-reduction equation. d. half-reaction. 43. The sum of the oxidation numbers for all atoms in a polyatomic ion is equal to a. -2 b. 0. c. the charge on that ion. d. the charge of the products. 44. The sum of the oxidation numbers for all the atoms in a molecule is equal to a. -2. b. 0. c. the charge on that ion. d. the charge of the products. 45. If oxidation is taking place, what also must be occurring? a. electroplating b. corrosion c. electrolysis d. reduction 46. Another name for an oxidation-reduction reaction is a. oxidizing agent. b. redox reaction. c. reducing agent. d. half-reaction. 47. The oxidation number of uncombined iodine a. 0. b. -1. c. -2. d. +1. 48. The element sulfur can exist in all of the following oxidation states except a. -2. b. +4. c. +5 d. +6. 49. When Cr 3+ changes to Cr 0, the chromium ion is said to have been a. oxidized because it gained 3e. b. oxidized because it lost 3e. c. reduced because it gained 3e. d. reduced because it lost 3e.
50. The term oxidation arose early in the history of chemistry, when scientists observed elements combining with oxygen in combustion reactions. For example, S(s) + O 2 (g) SO 2 (g). In this reaction, a. the oxygen is oxidized and the sulfur is oxidized. b. the oxygen is oxidized and the sulfur is reduced. c. the oxygen is reduced and the sulfur is reduced. d. the oxygen is reduced and the sulfur is oxidized.
SCHOOL YEAR 2017-18 NAME: CH- 20 ELECTROCHEMISTRY SUBJECT: CHEMISTRY GRADE: 12 TEST A Choose the best answer from the options that follow each question. 1. The following pair of half-reactions occurs in an electrochemical cell. Ag + + e Ag H 2 S S + 2H + + 2e Where does the silver half-reaction take place? a. at the anode b. at the cathode c. in the salt bridge d. on the wire 2. An electrochemical cell reacts according to the following equation: What is its cell notation? a. Br Br 2 Zn Zn 2+ b. Br Zn 2+ Zn Br 2 c. Zn2 Zn Br 2 Br d. Zn Zn 2+ Br Br 2 Br 2 + Zn 2Br + Zn 2+ 3. In an electrolytic cell, positive ions move toward the a. anode, and negative ions move toward the cathode. b. cathode, and negative ions also move toward the cathode. c. anode, and negative ions also move toward the anode. d. cathode, and negative ions move toward the anode. 4. In an electroplating cell, a solution of the salt of the plating metal is the a. cathode. b. anode. c. electrolyte. d. salt bridge. 5. When electricity is supplied to a rechargeable battery from an outside source, the battery acts as a(n) a. half-cell. b. voltaic cell. c. electrolytic cell. d. fuel cell.
Use the table below to answer the following questions. STANDARD REDUCTION POTENTIALS Half-cell reaction Standard electrode potential, E 0 (V) Half-cell reaction Standard electrode potential, E 0 (V) F 2 + 2e F +2.87 Fe 3+ + 3e Fe 0.04 MnO + 8H + + 5e Mn 2 + 4H 2 O +1.50 Pb 2+ + 2e Pb 0.13 Au 3+ + 3e Au +1.50 Sn 2+ + 2e Sn 0.14 Cl 2 + 2e 2Cl +1.36 Ni 2+ + 2e Ni 0.26 Cr 2 O + 14H + + 6e 2Cr 3+ + +1.23 Co 2+ + 2e Co 0.28 7H 2 O MnO 2 + 4H + + 2e Mn 2+ 2H 2 O +1.22 Cd 2+ + 2e Cd 0.40 Br 2 + 2e 2Br +1.07 Fe 2+ + 2e Fe 0.45 Hg 2+ + 2e Hg +0.85 S 2+ + 2e S 2 0.48 Ag + + e Ag +0.80 Cr 3+ + 3e Cr 0.74 Hg + 2e 2Hg +0.80 Zn 2+ + 2e Zn 0.76 Fe 3+ + e Fe 2+ +0.77 Al 3+ + 3e Al 1.66 MnO + e MnO +0.56 Mg 2+ + 2e Mg 2.37 I 2 + 2e 2I +0.54 Na + + e Na 2.71 Cu 2+ + 2e Cu +0.34 Ca 2+ + 2e Ca 2.87 Cu 2+ + e Cu + +0.15 Ba 2+ + 2e Ba 2.91 S + 2H 2 (aq) + 2e H 2 S(aq) +0.14 K + + e K 2.93 2H + (aq) + 2e H 2 0.00 Li + + e Li 3.04 6. Using the table above, what is the E for the cell Al Al 3+ Au 3+ Au? a. +0.24 V b. 0.24 V c. 3.08 V d. +3.08 V 7. Using the table above, what is the E for the cell Zn Zn 2+ Hg 2+ Hg? a. +1.56 V b. 1.56 V c. +0.04 V d. 0.04 V 8. Using the table above, what is the E for the cell Li + Li Ni 2+ Ni? a. 0 V b. 2.81 V c. +2.81 V d. 3.27 V
9. Based on E 0 values, which of the following metals is the most easily reduced? a. mercury b. sodium c. zinc d. gold 10. Which of the following would best protect iron from corrosion? a. Ca b. Zn c. Cu d. Ag Choose the best answer from the options that follow each question. 11. If the reactants of a voltaic cell are in contact, a. hydrogen gas is generated at the cathode. b. most of the energy produced is heat. c. the redox reaction will not occur. d. all of the energy will flow as electric current. 12. Which of the following is not true of a fuel cell? a. Water is a by-product of the reaction. b. Electricity is required to produce a chemical reaction. c. Reactants are continuously supplied and products are continuously removed. d. It acts as a voltaic cell. 13. In which type of cell does a current drive a nonspontaneous redox reaction? a. alkaline dry cell b. electrolytic cell c. fuel cell d. galvanic cell 14. What is the anode half-reaction for the cell a. Cu(s) Cu 2+ (aq) + 2e b. Cu 2+ (aq) + 2e Cu(s) c. Ag + (aq) + e Ag(s) d. Ag(s) Ag + (aq) + e 15. The cathode in a zinc-carbon dry cell is a. auto-oxidizing. b. the carbon electrolyte. c. the carbon electrode. d. the zinc electrode. Cu(s) Cu 2+ (aq) Ag + (aq) Ag(s)? 16. Which process breaks down a compound into its elements? a. electrolysis b. electroplating c. corrosion d. reduction
17. The production of aluminum from bauxite ore is a. a spontaneous process. b. inexpensive. c. the result of auto-oxidation. d. the result of an electrolytic process. 18. The electrolysis of water a. is a spontaneous process. b. produces oxygen gas at the cathode. c. produces both oxygen and hydrogen gas at the cathode. d. produces hydrogen gas at the cathode. 19. Corrosion is the disintegration of metals caused by a. electroplating. b. combustion. c. reduction. d. oxidation. 20. Chemical energy is converted into electrical energy in a(n) a. half-cell. b. voltaic cell. c. electrolytic cell. d. electroplating cell. 21. The half-reaction in a voltaic cell that has the more negative standard reduction potential will be a. the anode. b. the cathode. c. indicating electron loss. d. Both (b) and (c) 22. A corroding piece of steel is an example of a(n) a. galvanic cell. b. electrode. c. electrolytic cell. d. fuel cell. 23. In an electroplating cell, the object to be plated is the a. anode. b. cathode. c. electrolyte. d. salt bridge. 24. In which direction do electrons move in a voltaic cell? a. from the anode to the cathode b. from the cathode to the anode c. from the battery to the anode d. from the cathode to the electrolyte 25. Which occurs in a car s battery as the engine is started? a. Energy of motion is converted to energy in the form of heat. b. Chemical energy is converted to energy of motion. c. Chemical energy is converted to electrical energy. d. Electrical energy is converted to chemical energy.
TEST B PART I Choose the best answer from the options that follow each question. 1. In a cell used to electroplate silver onto an object, silver is deposited on the object at the a. anode, where it is oxidized. b. anode, where it is reduced. c. cathode, where it is oxidized. d. cathode, where it is reduced. 2. When a rechargeable cell is being recharged, the cell acts as a(n) a. electrochemical cell. b. electrolytic cell. c. voltaic cell. d. half-cell. 3. The half-reactions in the standard automobile battery use a. lead(iv) oxide, lead, and sulfuric acid. b. copper(ii) oxide, copper, and sulfuric acid. c. zinc oxide, zinc, and sulfuric acid. d. iron(iii) oxide, iron, and sulfuric acid. 4. If the calculated value for E is negative, the reaction a. occurs naturally in the direction written. b. will not occur spontaneously in a voltaic cell. c. can not occur in an electrolytic cell. d. will occur naturally in an electrolytic cell. 5. Given the cell notation Cu(s) Cu 2+ (aq) Ag + (aq) Ag(s), what is the half-reaction that occurs at the anode? a. Cu 2+ (aq) + 2e Cu(s) b. Cu(s) Cu 2+ (aq) + 2e c. Ag + (aq) + e Ag(s) d. Ag + (aq) + Cu(s) Ag(s) + Cu 2+ (aq) 6. What is the for the spontaneous reaction when a Ni 2+ / Ni half-cell is joined to a Cu 2+ / Cu half-cell? = +0.34 V and = 0.26 V. a. 0.08 V b. +0.08 V c. +0.60 V d. 0.60 V 7. What substance forms at the cathode during the electrolysis of water? a. hydrogen gas b. hydronium ions c. oxygen gas d. hydrogen peroxide 8. Which metal can be extracted from bauxite, using an electrolytic process? a. carbon b. zinc
c. gold d. aluminum 9. Galvanized steel is protected from corrosion because a. steel is more easily oxidized than zinc. b. zinc acts as a sacrificial anode. c. the steel is protected from sunlight. d. zinc has a more positive reduction potential than iron. 10. Which of the following is not an example of a voltaic cell? a. fuel cell b. electroplating cell c. rusting iron bar d. mercury battery PART II Write the correct term (or terms) in the space provided. 11. The electrode at which reduction occurs is the. 12. The branch of chemistry that deals with all electricity-related applications of oxidation-reduction reactions is called. 13. If reactants in a spontaneous energy-releasing oxidation-reduction reaction are connected externally by a wire conductor, energy is released as. 14. In a voltaic cell, the half-reaction with the lower standard reduction potential takes place at the. 15. If the redox reaction in an electrochemical cell occurs naturally and produces electric energy, the cell is a(n). 16. In a zinc-carbon dry cell, the zinc container serves as the. 17. The difference in potential between an electrode and its solution is the. 18. A process in which metal is deposited onto a surface by a nonspontaneous redox reaction is. 19. The standard reference electrode for measuring electrode potentials is called a(n). PART III Tell whether the following reactions would occur at the anode or the cathode of a voltaic cell. 20. Br 2 + 2 2Br 21. Fe 2+ + 2e Fe 22. Fe 2+ Fe 3+ + e In the space provided, label each of the following statements as True or False.
23. E 0 is positive for an electrolytic cell. 24. All car batteries act as voltaic cells. 25. Electron transfer in a voltaic cell occurs via external wires. Use the diagram of a voltaic cell to answer the questions. Recall that zinc is more active than copper as a reducing agent. The reaction that occurs is Zn(s)Cu 2+ (aq) Cu(s)Zn 2+. 26. Which metal strip is the anode? 27. Write the half-reaction that takes place at the cathode. 28. The electrons will flow from the electrode to the electrode. 29. Sulfate ions in solution will move away from the electrode and toward the electrode. PART IV Write the answers to the following questions in the space provided. 30. In which direction do positive ions flow in a voltaic cell? 31. What is the purpose of the salt bridge in an electrochemical cell? PART V Use the information below to answer the following questions. The following overall reaction takes place in an electrochemical cell: 3KMnO 4 (aq) + 24HCl(aq) + 5Al(s) 5AlCl 3 (aq) + 3MnCl 2 (aq) + 3KCl(aq) + 12H 2 O(l) 32. Write the balanced anode half-reaction. 33. Write the balanced cathode half-reaction. 34. Determine the value of E. Show your work. E = +1.50 V and E = 1.66 V
35. How can the spontaneity of this reaction be determined? 36. What type of cell would this be?