Swimming pool water can be made free from harmful bacteria by adding aqueous sodium chlorate(I), $\text{NaOCl}$. In water, this forms $\text{HOCl}$ molecules, and these kill bacteria. $\text{OCl}^-\text{(aq)} + \text{H}_2\text{O} \rightleftharpoons \text{OH}^-\text{(aq)} + \text{HOCl}\text{(aq)}$ Under bright sunshine, the $\text{OCl}^-$ ion is decomposed by ultra-violet light. $\text{OCl}^-\text{(aq)} + \text{uv light} \rightarrow \text{Cl}^-\text{(aq)} + \tfrac{1}{2}\text{O}_2\text{(g)}$ Which approach would keep the concentration of $\text{HOCl}\text{(aq)}$ at the highest level?
- Aacidify the pool water
- Badd a solution of chloride ions
- Cadd a solution of hydroxide ions
- Dbubble air through the water