500 mL of 2 M HCl, 100 mL of 2 M `H_(2)SO_(4)` and one gram equivalent of monoacidic alkali are mixed together. 30 mL of this solution required 20 mL of `Na_(2)CO_(3). xH_(2)O` solution obtained by dissolving 143 g `Na_(2)CO_(3).xH_(2)O` in one litre solution. Calculate the water of crystallisation of `Na_(2)CO_(3) .xH_(2)O`.