Oxidation-reduction reaction spontaneous, generating electricity from

Electrochemistry is best defined as the study of the interchange of chemical and electrical energy. It is primarily concerned with two processes that involve oxidation-reduction reactions the generation of an electric current from a spontaneous chemical reaction and the opposite process, the use of a current to produce chemical change. 

We can generate electrical energy from a spontaneous oxidation-reduction reaction by using an apparatus called a voltaic cell. The two half-reactions stiU take place, but in a cell the electrons must flow through an external circuit. For example, a piece of zinc metal in a Cu solution becomes coated with a rusty-brown coating of Cu, while the blue color (Cu ) of the solution fades. The oxidation of the zinc metal provides electrons for the reduction of the Cu ions. We can write the two half-reactions as... 

The energy available from spontaneous cell reactions can be used to power vehicles or generate electricity (Box 12.2). To calculate the standard cell potential for a spontaneous process, we must combine the standard potential of the cathode half-reaction (reduction) with that of the anode half-reaction (oxidation) in such a way as to obtain a positive... 

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