1. Gypsum is used in the preparation of calcium sulphate hemihydrate.
 
2. When you mix oxalic acid with water, you get a lot of heat.
 
3. \((CaSO_4)_2.H_2O + 3H_2O\) is the product obtained when \(2CaSO_4.2H_2O\) is heated to \(373K\).