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

To balance the redox reaction between chlorine (Cl₂) and sulfur dioxide (SO₂) in water, we will follow these steps:

### Step 1: Write the unbalanced equation
The initial unbalanced equation for the reaction can be written as:
\[ \text{Cl}_2 + \text{SO}_2 + \text{H}_2\text{O} \rightarrow \text{Cl}^- + \text{SO}_4^{2-} + \text{H}^+ \]

### Step 2: Assign oxidation states
- In Cl₂, the oxidation state of Cl is 0.
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