What acid is formed when chlorine is combined with water, alongside hydrochloric acid?

When chlorine gas is dissolved in water, it reacts with the water to form two primary products: hydrochloric acid (HCl) and hypochlorous acid (HClO). Hypochlorous acid is a weak acid and is significant in various applications, particularly in disinfection processes due to its ability to kill bacteria and viruses.

The formation of hypochlorous acid is vital in water treatment and sanitation practices, as it plays a role in maintaining safe drinking water and effective swimming pool sanitation. The presence of this acid is what makes chlorine an effective disinfectant, as it helps to maintain a balance between the strong oxidative properties of chlorine and the effective microbial inactivation properties of hypochlorous acid.

The other options listed do not represent acids that are commonly associated with a chlorine and water reaction. Hypochloric or hyperclorous acids are not recognized compounds in this context, and hydrachloric is likely a misnaming of hydrochloric acid. Thus, the clear and relevant acid formed through the combination of chlorine and water is indeed hypochlorous acid.