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Unformatted text preview: 370 Chapter 21 Electrochemistry Some of the most useful and common practical applications of chemistry involve the use of or production of electricity. Chemical reactions that produce electrical power in batteries start our cars, run electronic calcula-tors and portable radios, keep wristwatches running, and set proper exposures in cameras. Our lives are touched constantly by the ultimate fruits of electrolysis reactions, such as aluminum, bleach, halogenated or-ganic molecules in plastics and insecticides, and soap. Besides all of these things, the relationship between electricity and chemical change has become an extremely useful tool in the laboratory for probing chemical systems of all kinds. Learning Objectives As you study this chapter, keep in mind the following goals: 1 To learn about the kinds of chemical reactions that can be studied electrically. 2 To learn how a spontaneous redox reaction can be set up to deliver electrical energy in a galvanic cell. 3 To learn to describe a galvanic cell using standard cell notation. 4 To see how the voltage, or potential, of a galvanic cell can be considered to arise as the difference between the potentials that each half-cell has for reduction. 5 To learn how reduction potentials are measured by comparison to a standard electrode called the hydrogen electrode. 6 To learn how to use standard reduction potentials to predict the spontaneous cell reac-tion, the cell potential, and whether or not a given reaction will proceed spontaneously. 7 To learn how to calculate G from a cell potential, and vice versa. 8 To learn how to calculate an equilibrium constant from the standard cell potential. 9 To learn how to calculate the effect on the cell potential of changing the concentrations of the ions in a galvanic cell. 10 To learn the chemistry of some common types of batteries and to look at possible future developments. 11 To learn what electrolysis is, to study how an electrolysis apparatus (electrolysis cell) is constructed, and to learn how to write equations for the reactions that take place in an electrolysis cell. 12 To learn how to use standard cell potentials to predict the products of electrolysis. 13 To learn how to compute the amount of chemical change caused by the flow of a given amount of electricity. 14 To study various practical applications of electrolysis. Chapter 21 371 21.1 Galvanic cells use redox reactions to generate electricity Review Electrical devices operate by the flow of electrons; thats what electricity is. Reactions that produce or con-sume electrical energy are called electrochemical changes . They are oxidation-reduction reactions, and their study constitutes the field of electrochemistry . As we discuss in this chapter, the applications of electrochem-istry affect our daily lives as well as our activities in the laboratory....
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