Why bleaching powder smell strongly of chlorine and does not dissolve completely in water?

Bleaching Powder (CaOCl₂) reacts with carbon dioxide from the atmosphere to produce calcium carbonate and chlorine gas. This is why bleaching powder gives the smell of chlorine.

​ $CaOCL_{2} +CO_{2}\rightarrow \ CaCO_{3} +Cl_{2} \uparrow $

Bleaching powder is also called chloride of lime. It is actually a mixture of calcium chloride, calcium hydroxide, and calcium hypochlorite. It is not completely soluble in water as it composed of heavy salts, which are known to be insoluble in water.