A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z.

Soln:

X is Calcium . When calcium carbonate reacts with HCl it gives out CO₂ gas. CaCO₃ + HCl CaCl₂+CO₂+H₂O

When CO2 is passed into lime water it turns milky due to formation of Calcium carbonate. Hence solution Y is lime water

When chlorine gas is passed on dry lime water it gives bleaching powder which is used for disinfecting water.