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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:
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
The balanced chemical equation can be obtained by adding equation (i) and (ii) as:
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