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, gives a compound Z, Z is used for disinfecting drinking water. Identify X, Y, G and Z.

Explanation

The gas evolved at anode during electrolysis of brine is chlorine (G)
When chlorine gas is passed through dry `Ca(OH)_(2)` (Y) products bleaching powder (Z) used for disinfecting drinking water.
`underset("Slaked lime")(Ca(OH)_(2)) + Cl_(2) rarr underset("Bleaching powder")(CaOCl_(2) + H_(2)O)`
Since Y and Z are calcium salts, therefore X is also a calcium salt and is calcium carbonate.
`CaCO_(3) + 2HCl rarr CaCl_(2) + CO_(2) + H_(2)O`
`Ca(OH)_(2) + CO_(2) rarr CaCO_(3) + H_(2)O`