What happens to chlorine when it comes into contact with water?

When chlorine comes into contact with water, it undergoes a chemical reaction to form hypochlorous acid (HClO). This reaction is essential for its function as a disinfectant in pool maintenance. The presence of hypochlorous acid is critical because it is the active form of chlorine that effectively kills bacteria, viruses, and other pathogens in the water.

This transformation emphasizes the importance of proper chemical balance in pool water, as hypochlorous acid is much more effective at lower pH levels, ensuring better disinfection. Understanding this reaction is vital for pool operators, as maintaining appropriate chlorine levels ensures the safety and cleanliness of the water.

Other choices do not accurately describe the behavior of chlorine in water. For instance, while chlorine can dissipate into the air, it does not quickly evaporate when introduced to water. The formation of sodium chloride involves different conditions, typically when chlorine reacts with sodium in a completely different process. Additionally, while chlorine can react with impurities in the water, the primary and most significant reaction when chlorine meets water is the generation of hypochlorous acid, making it the most relevant and correct answer in this context.