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.

Explanation

The skeletal equation is
`Cl_(2)(aq)+SO_(2)(aq)+H_(2)O(l)toCl^(-)(aq)+SO_(4)^(2-)(aq)`
Balance the equation by ion-electron method as described in . The balanced equation is
`Cl_(2)(aq)+SO_(2)(a)+2H_(2)O(l)to2Cl^(-)(aq)+SO_(4)^(2-)(aq)+4H^(+)(aq)`