Electrolytic Cells Using Electrical Energy to Drive Nonspontaneous Reactions

7 ELECTROLYTIC CELLS USING ELECTRICAL ENERGY TO DRIVE NONSPONTANEOUS REACTIONS 

Up to now, we ve been considering voltaic cells, those that generate electrical energy from a spontaneous redox reaction. The principle of an electrolytic cell is exactly the opposite electrical energy from an external source drives a nonspontaneous reaction. 

CHAPTER 21 Electrochemistry Chemical Change and Electrical Work 

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Electrolytic Cells Using Electrical Energy to Drive Nonspontaneous Reactions... 

An electrolytic cell uses electrical energy to drive a nonspontaneous reaction. Oxidation occurs at the anode and reduction at the cathode, but the direction of electron flow and the charges of the electrodes are opposite those in voltaic cells. In electrolysis of a pure molten salt, the metal cation is reduced at the cathode, and the nonmetal anion is oxidized at the anode. 

Recall that the voltaic cells convert chemical energy to electrical energy as a result of a spontaneous redox reaction. Electrolytic cells do just the opposite they use electrical energy to drive a nonspontaneous reaction. A common example is the electrolysis of water. In this case, an electric current decomposes water into hydrogen and oxygen. 

Voltaic cells are based on spontaneous redox reactions. It is also possible for nonspontaneous redox reactions to occur, however, by using electrical energy to drive them. For example, electricity can be used to decompose molten sodium chloride into its component elements Na and CI2. Such processes driven by an outside source of electrical energy are called electrolysis reactions and take place in electrolytic cells. 

Electrolysis is the use of electric energy to drive a nonspontaneous redox reaction. An electrochemical cell used for this purpose is called an electrolytic cell... 

Electrochemistry is the area of chemistry concerned with the interconversion of chemical and electrical energy. Chemical energy is converted to electrical energy in a galvanic cell, a device in which a spontaneous redox reaction is used to produce an electric current. Electrical energy is converted to chemical energy in an electrolytic cell, a cell in which an electric current drives a nonspontaneous reaction. It s convenient to separate cell reactions into half-reactions because oxidation and reduction occur at separate electrodes. The electrode at which oxidation occurs is called the anode, and the electrode at which reduction occurs is called the cathode. 

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