  Question

# 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.

Solution

## The given redox reaction can be represented as: Cl2(s)+SO2(aq)+H2O(l)⟶Cl−(aq)+SO2−4(aq) The oxidation half reaction is: +4SO22(aq)⟶+6SO2−4(aq) The oxidation number is balanced by adding two electrons as: SO2(aq)⟶SO2−4(aq)+2e− The charge is balanced by adding 4H+ ions as: SO2(aq)+2H2O2−4(aq)+4H+(aq)+2e− The O atoms and H+ ions are balanced by adding 2H2O molecules as: SO2(aq)+2H2O(l)⟶SO2−4(aq)+2e−   ⋯(i) The reduction half reaction is: 0Cl2(s)⟶−1Cl−(aq) The oxidation number is balanced by adding electrons Cl2(s)+2e−⟶2Cl−(aq)  ⋯(ii) The balanced chemical equation can be obtained by adding equation (i) and (ii) as: Cl2(s)+SO2(aq)+2H2O(l)⟶2Cl−(aq)+SO2−4(aq)+4H+(aq)  Suggest corrections  Similar questions
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