Question

What is the cause for the bleaching action of chlorine?

Answer 1

Chlorine reacts with moisture and forms hydrochloric acid and hypochlorous acid.

$C{l}_2+H_{2}O\to HCl+HClO$

Hypochlorous acid (HClO) is unstable, so it breaks down into HCl and nascent oxygen [O]

$HClO\to HCl+\left[O\right]$
The nascent oxygen is a powerful bleaching agent and is responsible for the bleaching action.