Answer question numbers (a), (d) on the basis of your understanding of the following paragraph and related studied concepts. Copper sulphate crystals which seem to be dry contain water of crystallisation. When we heat the crystals, this water is removed and the salt turns white. If you moisten the crystals again with water, you will find that blue colour of the crystals reappears. Water of crystallisation that is the fixed number of water molecules present in one formula unit of a salt. Five water molecules are present in one formula unit of copper sulphate. Chemical formula for hydrated copper sulphate is CusO_(4).5H_(2)O. Now you would be able to answer the question whether the molecule of Na_(2)CO_(3).10H_(2)O is wet. One other salt, which possesses water of crystallisation is gypsum. It has two water molecules as water of crystallisation. It has the chemical formula CaSO_(4).2H_(2)O What will happen if gypsum is heated to 373 K and above ?