$$ extbf{Concept:}$$ Bleaching powder is produced by the reaction of calcium hydroxide with chlorine. Calcium hydroxide is also known as slaked lime. When chlorine gas is passed over the dry slaked lime thus bleaching powder and water is produced. $$ullet$$When calcium carbonate reacts with hydrochloric acid, it gives carbon dioxide gas. $$mathrm{CaCO}_{3}+2 mathrm{HCl} \rightarrow mathrm{CaCl}_{2}+mathrm{CO}_{2}+mathrm{H}_{2} mathrm{O}$$ $$ullet$$When carbon dioxide is passed through limewater, the limewater turns milky. This happens because of the formation of calcium carbonate. $$mathrm{CO}_{2}+mathrm{Ca}(mathrm{OH})_{2} \rightarrow mathrm{CaCO}_{3}+mathrm{H}_{2} mathrm{O}$$ $$ullet$$On electrolysis of brine, chlorine gas is obtained at the anode. When chlorine gas is passed through limewater, it gives bleaching powder. $$mathrm{Ca}(mathrm{OH})_{2}+mathrm{Cl}_{2} \rightarrow mathrm{CaOCl}_{2}+mathrm{H}_{2} mathrm{O}$$ $$ullet$$X is calcium carbonate. Y is limewater. G is chlorine. Z is bleaching powder.