Question

what happens when bleaching powder is kept open in air

Answer 1

Bleaching powder is a yellowish whitepowder with a strong smell of chlorine. When exposed to air, bleaching powder gives a smell of chlorine. This is because bleaching powder reacts with carbon dioxide from the atmosphere to produce calcium carbonate and chlorine.

Answer 2

Bleaching powder is hygroscopic so when kept open to air it absorbs moisture from atmosphere and becomes soggy over a period of time. As it absorbs moisture it loses chlorine and thus loses its property.