Electrolysis

Spontaneous redox reactions in voltaic cells convert chemical energy into electrical energy. Alternatively, external electrical energy drives nonspontaneous redox reactions in a process called electrolysis, taking place in an electrolytic cell.

An electrolytic cell has an anode for oxidation and a cathode for reduction. However, unlike the voltaic cell, where the negatively charged anode is the source of electrons, the electrolytic cell has an external source of electrons like a battery.

The battery draws electrons from the anode connected to its positive terminal and drives electrons towards the cathode, which is connected to its negative terminal. Thus electrons flow from the positive to the negative terminal of the external power source.

Electrolysis is used to separate ionic compounds into their constituent elements. In their molten or aqueous state, the constituent ions are free to conduct electricity.

Consider potassium bromide that melts at a temperature of 734 °C. Here, bromide and potassium ions are present at their lowest or highest oxidation state, respectively. Under power, the bromide ions are oxidized to bromine gas at the anode, and potassium ions are reduced to soli