Introduction

Dry cells power our everyday electrical and electronic equipment because a chemical reaction inside them generates electricity — in a dry cell, chemical energy is converted into electrical energy. Electrolysis works the opposite way: it is the breaking down of an ionic compound by the passage of electricity, so that electrical energy is converted into chemical energy. Electrochemistry is the area of chemistry concerned with this interconversion of chemical and electrical energy.

It also deals with the resistance and conductance of aqueous electrolytic solutions — determining the conductivity of an electrolytic solution tells us about the extent of ionization of the electrolyte in water (refer to Chapter 3).

The study of electrochemical cells matters in science and technology because it makes the manufacture of essential chemicals possible. NaOH — widely used in making soaps, detergents and paper — is prepared by the electrolysis of NaCl, and electrolysis is possibly the only means to produce fluorine. Electro-refining (purification of metals) and electroplating (coating one metal on the surface of another) are also electrochemical processes.

In Standard XI you learnt redox reactions. A redox reaction forms the basis both for the generation of electricity by a chemical reaction and for chemical reactions brought about by means of electricity; these processes are carried out in an electrochemical cell, and electrochemistry deals with the design and operation of such cells. Current research in the field is focused on the design of fuel cells, which are being explored as a convenient and compact source of electricity.