A white solid (x) when heated evolves a colourless gas which does not support combusion. The residue tis dissolved in water to form (y) which can be used for white washing. When excess of `CO_(2)` is bubbled through the solution of (y), it gives a compound (z) which upon heating forms (x) Identify the compound (x).

Explanation

The data suggests that the compound (x) is lime stone i.e., `CaCO_(3)` and the gas evoloved is carbon dioxide. The reaction that are taking place are as follows "
`underset((x))(CaCO_(3)) overset("Heat")(to) CaO + CO_(2) , CaO + H_(2)O to underset((y))(Ca(OH)_(2))`
`Ca(OH)_(2) + CO_(2) + H_(2)O to Ca(HCO_(3))_(2)`
`underset((z))(Ca(HCO_(3))_(2)) overset("Heat")(to) underset((x))(CaCO_(3)) + H_(2)O + CO_(2)`