Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with Sulphur dioxide. Present a balanced equation for this redox change taking place in water.

The given redox reaction can be represented as follows:-

The oxidation half reaction is:-

The oxidation number is balanced by adding two electrons as:-

The charge is balanced by adding 4H⁺ ions as:-

The O atoms and H⁺ ions are balanced by adding 2H₂O molecules as:-

The reduction half reaction is:-

The chlorine atoms are balanced as:-

The oxidation number is balanced by adding electrons as:-

The balanced chemical equation can be obtained by adding oxidation and reduction half equations to get the desired equation as: -