The compound `"A"` on heating gives a colourless gas and a residue which dissolves in water to give B. When excess of `CO_(2)` is passed into B and gently heated, A is formed.The compound A is

The compound A on heating gives a colourless gas and a residue that is dissolved in water to obtain B. Excess of CO_(2) is bubbled through aqueous solution of B,C is formed which is recovered in the solid form.Solid C on gentle heating gives back A. The compound is

A compound X on heating gives a colourless gas. This residue is dissolved in water to obtain Y. excess CO_(2) is bubbled through aqueous solution of Y, Z is formed. Z on gentle heating give back X. the X is

A solid compound X on heating gives CO_(2) gas and a residue. When mixed with water it forms Y. On passing excess of CO_(2) through Y in water a clear solution of Z is obtained. On boiling Z compound X is reformed. Compound X is

A solid compound X on heating gives CO_(2) gas and a residue. The residue mixed with water forms Y. On passing excess of CO_(2) through Y in water, a clear solution Z is obtained. On boiling Z, compound X is reformed. The compound X is

A solid compound 'X' on heating gives CO_(2) gas and a residue. The residue mixed with water forms 'Y' . On passing an excess of CO_(2) through 'Y' in water , a clear solution, 'Z' is obtained. On boiling 'Z' , compound 'X' is reformed. The compound 'X' is