If the water of crystallisation in gypsum is X and Y in washing soda then the value of X + Y is ________.
The number of molecules of water of crystallisation present in washing soda crystals is :
(a) five
(b) two
(c) ten
(d) seven
How many molecules of water of crystallisation (per formula unit) are present in (a) copper sulphate crystals (b) washing soda (c) gypsum ? [3 marks]