CBSE Class 10 Answered

The metal carbonate x is CaCO3. When it reacts with an acid, produces a salt , water and CO₂ which when passed through a solution y that is Ca(OH)₂ [ slaked lime ] gives back the carbonate.

CaCO3 + HCl -> CaCl + H₂O +C

x + acid -> CaCl + H₂O + CO₂

CO ₂ + Ca(OH) ₂ -> CaCO3 + H ₂ O

y

CaCO3 is limestone

Chlorine is generated on anode when electrolysis of brine is carried out. 2Cl^- - 2e^- ? Cl2

When it is passed over dry CaCO3, it forms Z, which is CaOCl2.

Ans 2 

Sodium hydroxide (NaOH) is a commonly used base and it absorbs moisture from the atmosphere and becomes sticky. 

The acidic oxides react with base to give salt and water. Lets take an acidic oxide- Carbon dioxide. The reaction between NaOH and CO2 can be given as

2 NaOH + CO₂ ---------> Na₂CO₃ + H₂O .