Verified answer

Answer

Molar mass of Na2CO3.2H2O is 142 g / mol [ Na=23 C=12 O=16 H=1 , 2H2O= 36. Na2 = 46. CO3 = 60, total 142 g / mol ]

[Out of this Na2CO3 is 106 g / mol and water is 36 g / mol of hydrated sod carbonate. Anhydrous Na2CO3 in Na2CO3.2H2O is 106/142 = 74.65% ]

2 M Na2CO3 solution would require, 2*106 g anhydrous Na2CO3 / lit solution. That is , we need 212 g

anhydrous Na2CO3, this is eqiv to 212/0.7465 = 284 g , 100% purity Na2CO3.2H2O

At 98.5% purity , we would require 284/0.985 = 288.33 g Na2CO3.2H2O to make 1 lit 2M solution