What Is Electrochemistry?

Electrochemistry is the sub discipline of chemistry that deals with the study of the relationship between electrical energy and chemical changes. Chemical reactions that involve the input or generation of electric currents are called electrochemical reactions. Such reactions are broadly classified into two categories:

1. Production of chemical change by electrical energy i.e. the phenomenon of electrolysis
2. Conversion of chemical energy into electrical energy. i.e., the generation of electricity by spontaneous redox reactions.

Electricity can be produced when electrons move from one element to another in certain types of reactions (such as redox reactions). Typically, electrochemistry deals with the overall reactions when multiple redox reactions occur simultaneously, connected via some external electric current and a suitable electrolyte. In other words, electrochemistry is also concerned with chemical phenomena that involve charge separation (as seen commonly in liquids such as solutions). The dissociation of charge often involves charge transfer that occurs homogeneously or heterogeneously between different chemical species.

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Electrochemical Cell

A spontaneous chemical process is the one which can take place on its own and in such a process Gibbs free energy of a system decreases. In electrochemistry, spontaneous reaction (redox reaction) results in the conversion of chemical energy into electrical energy. The reverse process is also possible where a non-spontaneous chemical reaction occurs by supplying electricity. These interconversions are carried out in equipment called electrochemical cell.

Types of Electrochemical Cell

Electrochemical cells are of two types: galvanic cells and electrolytic cells

Galvanic Cell

The galvanic cell converts chemical energy into electrical energy i.e, electricity can be obtained with the help of redox reaction. The oxidation and reduction take place in two separate compartments. Each compartment consists of an electrolyte solution and metallic conductor which acts as an electrode. The compartment containing the electrode and the solution of the electrolyte is called half cells.

Electrolytic Cell

The electrolytic cell converts electrical energy to chemical energy. Here the electrodes are dipped in an electrolytic solution containing cations and anions. On supplying current the ions move towards electrodes of opposite polarity and simultaneous reduction and oxidation take place.

For example, in the electrolysis of molten sodium chloride, sodium chloride is melted (above 801^oC), two electrodes are inserted into the melt, and an electric current is passed through the molten salt.