Question

what is action of sulfuric acid on bleaching powder

Answer 1

The chlorine, produced by the action of a dilute acid on bleaching powder, acts as a bleaching agent (a substance which decolourises coloured substances is called a bleaching agent). The bleaching action of chlorine is due to itsoxidizing property.

Answer 2

Bleaching powder reacts with carbon dioxide and produce chlorine gas. ...Reaction with dilute sulphuric acid: When bleaching powder is treated with an excess of dilute sulphuric acid, all the chlorine present in it is liberated: The amount of chlorine thus set free is called "available chlorine" .