5g of crystalline salt rendered anhydrous; lost 1.8g of water. The formula weight of the anhydrous salts is 160. The number of water molecules of crystallization is:
(5-1.8) g of salt require 1.8 g of water
160g of salt requires × g of water.
= 160 × 1.83.2 = 90.0g
No. of water molecules =9018 = 5.