1. Chapter 11: Oxidation and Reduction The Electricity of Chemistry © 2003 John Wiley and Sons Publishers Courtesy Craig Aurness/Corbis Images

2. Figure 11.6: Zinc metal in copper sulfate solution. © 2003 John Wiley and Sons Publishers

6. Figure 11.4: A form of the Daniell cell. © 2003 John Wiley and Sons Publishers Courtesy Ken Karp

7. Electrochemical Cells 19.2 spontaneous redox reaction anode oxidation cathode reduction

9. Batteries Zn(Hg) + 2OH - (aq) ZnO (s) + H 2 O (l) + 2e - Anode: Cathode: HgO (s) + H 2 O (l) + 2e - Hg (l) + 2OH - (aq) Zn(Hg) + HgO (s) ZnO (s) + Hg (l) Mercury Battery 19.6

10. Batteries Anode: Cathode: Lead storage battery PbO 2 (s) + 4H + (aq) + SO 2- (aq) + 2e - PbSO 4 (s) + 2H 2 O (l) 4 Pb (s) + SO 2- (aq) PbSO 4 (s) + 2e - 4 Pb (s) + PbO 2 (s) + 4H + (aq) + 2SO 2- (aq) 2PbSO 4 (s) + 2H 2 O (l) 4

11. Figure 11.3: A clock run by a chemical reaction. © 2003 John Wiley and Sons Publishers Courtesy Skilcraft

15. What is the standard emf of an electrochemical cell made of a Cd electrode in a 1.0 M Cd(NO 3 ) 2 solution and a Cr electrode in a 1.0 M Cr(NO 3 ) 3 solution? Cd 2+ (aq) + 2e - Cd (s) E 0 = -0.40 V Cr 3+ (aq) + 3e - Cr (s) E 0 = -0.74 V Cd is the stronger oxidizer Cd will oxidize Cr E 0 = E cathode - E anode cell 00 E 0 = -0.40 – (-0.74) cell E 0 = 0.34 V cell

16. Alessandro Volta demonstrating his discovery to the French Academy in 1801. © 2003 John Wiley and Sons Publishers Courtesy Culver Pictures, Inc.

17. Electrolysis Electrolysis of Water: Requires an electrolyte species, that is less easily oxidized and reduced than water, to carry the current. Anode: Water is oxidized to oxygen gas. –2 H 2 O(l)  O 2 (g) + 4 H + (aq) + 4 e – Cathode: Water is reduced to hydrogen gas. –4 H 2 O(l) + 4 e –  2 H 2 (g) + 4 OH – (aq)

18. Figure 11.10: The electrolysis of water. © 2003 John Wiley and Sons Publishers Courtesy Yoav Levy/Phototake

19. Electrolysis of Water

20. Niagara Falls and Typhoid How Does Niagara Falls Helps to Fight Typhoid ?

21. 19.8 Electrolysis is the process in which electrical energy is used to cause a nonspontaneous chemical reaction to occur.

22. Electrolysis Electrolysis of Molten Sodium Chloride: Electrolysis of Aqueous Sodium Chloride: uses different processes to molten sodium chloride. The observed product at the anode is Cl 2, and Na metal at the cathod.

23. Galvanized tacks, drugstore iodine, and household bleach. © 2003 John Wiley and Sons Publishers Courtesy Ken Karp

24. Figure 11.1: Color changes with galvanized tacks, iodine, and household bleach. © 2003 John Wiley and Sons Publishers Courtesy Ken Karp

25. Figure 11.1: Color changes with galvanized tacks, iodine, and household bleach. © 2003 John Wiley and Sons Publishers Courtesy Ken Karp

26. © 2003 John Wiley and Sons Publishers What element forms the metal casing of a common flashlight battery? Name three compounds (other than water) that form the black paste held within this metal casing. What element forms the porous rod embedded in this paste? QUESTION

27. © 2003 John Wiley and Sons Publishers Would a Daniell cell work equally well if the salt bridge were replaced by a length of copper wire? Explain. QUESTION

28. © 2003 John Wiley and Sons Publishers We can infer that copper ions in water produce a blue color by noting that a solution of copper sulfate in water, which contains copper ions and sulfate ions, is blue and that a solution of zinc sulfate in water, which contains zinc ions and sulfate ions, is colorless. Why does this observation lead us to conclude that the copper ions of the copper sulfate solution produce the blue color? QUESTION

29. © 2003 John Wiley and Sons Publishers Suppose that as the zinc metal is converted into zinc ions (which are soluble in water) all the copper ions in solution are converted to copper metal. What new compound, a combination of a cation and a balancing anion, would then exist in the colorless solution? QUESTION

30. © 2003 John Wiley and Sons Publishers The reaction of calcium and chlorine described in Section 3.12 can be rewritten as Ca + Cl 2  CaCl 2. In this reaction, what is being oxidized? What is being reduced? Write reactions for the two half-cells of this redox reaction. QUESTION

31. © 2003 John Wiley and Sons Publishers We prepared the salt bridge of our Daniell cell by soaking a strip of cloth in a sodium chloride solution. As the cell begins to operate, would you expect the sodium and chloride ions of the bridge to move? If your answer is yes, which direction would the sodium ions move an in which direction would the chloride ions move? If your answer is no, explain why not. QUESTION

32. © 2003 John Wiley and Sons Publishers By increasing the areas of the zinc and copper plates in the Daniell cell, we can increase the amperage of the current flowing through the circuit without affecting the voltage we measure with the voltmeter. How does increasing the size of the zinc and copper plates affect the electrical pressure that moves the electrons along? How does increasing the size of the plates affect the rate of flow of the electrons through the circuit? QUESTION

33. © 2003 John Wiley and Sons Publishers Which element, atom, molecule, or ion in Table 11.1 is the strongest oxidizing agent? Which is the weakest? QUESTION

34. © 2003 John Wiley and Sons Publishers What is the most powerful reducing agent in Table 11.1? Explain. QUESTION

35. © 2003 John Wiley and Sons Publishers In section 10.2 we saw that acids liberate hydrogen gas when in contact with certain metals, such as iron and zinc. Using the data in Table 11.1, show that the reactions of iron, and zinc with an acid spontaneously generate hydrogen gas by redox reactions. Identify three other metals that will spontaneously liberate hydrogen gas from an acid. Identify three metals that will not. QUESTION

36. © 2003 John Wiley and Sons Publishers Which, if any, of the following metals will decolorize tincture of iodine: (a) nickel, (b) copper, (c) silver, (d) magnesium, (e) calcium? Explain your answer for each. QUESTION

37. © 2003 John Wiley and Sons Publishers Using the half-cell reactions of Table 11.1, write the redox reaction that would release the greatest amount of energy. That is, write the redox reaction that produces the greatest redox voltage. QUESTION

38. © 2003 John Wiley and Sons Publishers The Daniell cell itself isn’t used as a commercial battery. Suggest at least one reason why it isn’t. QUESTION

39. © 2003 John Wiley and Sons Publishers What change takes place in the composition of the battery fluid – the liquid that bathes the battery’s plates – as the battery is recharged by the generator or alternator? QUESTION

40. © 2003 John Wiley and Sons Publishers What three chemicals are produced through the electrolysis of sodium chloride solutions? What three chemicals would you expect to be produced by the electrolysis of a solution of sodium bromide? QUESTION

41. © 2003 John Wiley and Sons Publishers What is galvanized metal? Describe two ways galvanizing helps keep iron from rusting. QUESTION