Bromine water is brown and weakly acidic due to following equilibrium :
` underset( " Brown " ) (Br_2(aq) ) + 2H_2O hArr underset( " Colourless ")( HBrO(aq))+ H_3O^(+) (l) + underset( " Colourless ") (Br^(-)(aq)) `
When sodium hydroxide is added to the solution , the solution becomes colourless but the colour return when hydrochloric acid is added. Explain this observation.

Explanation

To explain the observation regarding the color change of bromine water when sodium hydroxide (NaOH) and hydrochloric acid (HCl) are added, we can analyze the equilibrium reaction and apply Le Chatelier's principle.

### Step-by-step Solution:

1. **Understanding the Equilibrium Reaction**:
The equilibrium reaction for bromine water is:
\[
\text{Br}_2(aq) + 2 \text{H}_2\text{O} \rightleftharpoons \text{HBrO}(aq) + \text{H}_3\text{O}^+(l) + \text{Br}^-(aq)
...