11.1 Electrochemistry - 11.1 Electrochemistry: How Does a...

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11.1 Electrochemistry: How Does a Battery Work? Objectives Write corrosion reactions. Calculate electrochemical cell potential. Predict which metal in a galvanic couple will corrode. Corrosion of metals is an electrochemical reaction, so in order to understand how corrosion works and how to prevent it, we need to understand the electrochemical reactions that occur. We begin by considering the following reaction: Zn (s) + Cu 2+ (aq) Zn 2+ (aq) + Cu (s) This reaction says that if you place zinc solid in a solution that contains Cu 2+ ions (like a solution of CuCl 2 ), you will end up dissolving some of the zinc to form zinc ions and depositing copper metal on the zinc. This is a reduction-oxidation reaction, or redox reaction , and it involves the transfer of electrons from one metal to the other. In order to see how the electrons are transferred, it is convenient to divide the redox reaction into its separate half-reactions . One half-reaction is a reduction reaction , in which a metal gains electrons. The other type of half-reaction is an oxidation reaction , in which a metal loses electrons. For the redox reaction shown above, the half reactions are: Reduction: Cu2+ (aq) + 2e- → Cu (s) Oxidation: Zn (s) → Zn2+ (aq) + 2e- If we add up these two half-reactions we get the overall redox reaction. We can remember which the is reduction and which is oxidation with some memory devices: OIL RIG = Oxidation Is Loss, Reduction Is Gain LEO the lion says GER = Loss of Electrons is Oxidation, Gain of Electrons is Reduction The metal that is oxidized is also called the reducing agent (because it reduces the other metal), while the metal that is reduced is called the oxidizing agent (because it oxidizes the other metal). GI 11.1.1. How many electrons are transferred between zinc and copper in the above reaction? GI 11.1.2 In the reaction between zinc and copper, which metal is oxidized and which metal is reduced? GI 11.1.3 In the reaction between zinc and copper, which metal is the oxidizing agent and which metal is the reducing agent?
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GI 11.1.4 When chromium is placed into a solution of CoCl 2 , cobalt metal is deposited on the chromium. Which substance is oxidized and which is reduced? Which is the oxidizing agent and which is the
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This note was uploaded on 04/12/2010 for the course EMA 3010 taught by Professor Douglas during the Spring '10 term at University of Hawaii - Hilo.

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11.1 Electrochemistry - 11.1 Electrochemistry: How Does a...

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