The reaction between Cl2 and H2O to form HClO is an example of a hydrolysis reaction. In a hydrolysis reaction, water reacts with a compound to break it down into its component parts. In this case, the water molecule reacts with the chlorine molecule to form hydrochloric acid (HCl) and hypochlorous acid (HClO).

The overall reaction can be represented as follows:

Cl2 + H2O → HCl + HClO

This reaction is important in the production of hydrochloric acid, which is a widely used industrial chemical. It is also important in the disinfection of water, as hypochlorous acid is a powerful oxidizing agent that can kill bacteria and other microorganisms.