A metal carbonate X on reacting with an acid gives a gas which when passed

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. Identify X, Y, G and Z.

Answer:

The gas evolved at anode during electrolysis of brine is chlorine (G).
When chlorine gas is passed through dry Ca(OH)2 (Y) produces bleaching powder (Z) used for disinfecting drinking water.
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Since Y and Z are calcium salts, therefore X is also a calcium salt and is calcium carbonate.
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