What chemical reaction occurs when chlorine is added to pool water?

When chlorine is added to pool water, it reacts with the water to form hypochlorous acid. This is a key part of pool sanitation, as hypochlorous acid is a powerful disinfectant that effectively kills bacteria, viruses, and other pathogens present in the water.

This reaction is crucial for maintaining safe swimming conditions. When chlorine (sodium hypochlorite or calcium hypochlorite, for example) dissolves in water, it interacts to create hypochlorous acid and hypochlorite ions. The presence of hypochlorous acid is what allows chlorine to effectively sanitize the pool, as it is the more active form of chlorine in terms of disinfection.

Other options describe different scenarios that do not accurately represent the primary reaction occurring with added chlorine. Understanding this reaction helps pool operators ensure effective water treatment and maintain hygiene standards.