(i) Sodium carbonate is a compound (X) which is used in glass and soap industry.
Its chemical formula is Na2CO3.
(ii) Ten molecules of water of crystallisation (i.e.10H2O) are present in this compound.
(iii) Ammonia and carbon dioxide gas is passed through brine solution (or sodium chloride solution). As a result, a mixture of NaHCO3 and NH4Cl formed.
On heating NaHCO3, sodium carbonate, water and carbon dioxide are formed.
Anhydrous sodium carbonate is dissolved in water. The solution is concentrated and upon cooling, it gives hydrated sodium carbonate (called washing soda).