What is formed when chlorine is added to water?

When chlorine is added to water, one primary product is hypochlorous acid (HClO), which is a weak acid formed due to the reaction of chlorine with water. This reaction can be represented by the equation:

Cl2 + H2O → HClO + HCl

In this reaction, both hypochlorous acid and hydrochloric acid (HCl) are formed, but hypochlorous acid is the more relevant acid in terms of disinfection and sanitation in water treatment processes. Hypochlorous acid plays a crucial role in killing bacteria and other pathogens, making the addition of chlorine an essential step in water purification.

While hydrochloric acid does form, the emphasis on hypochlorous acid is important because it is the primary active disinfecting agent resulting from this process. Therefore, stating that one acid is formed captures the essence of the primary reaction taking place when chlorine is introduced to water.