The water of crystallisation means having a fixed number of molecules present in one formula of a unit of salt.(i) Bleaching powder has the chemical formula ${\mathrm{CaOCl}}_2$. Its formula does not show any association with water molecules.(ii) Plaster of Paris has the chemical formula ${\mathrm{CaSO}}_4 \cdot \frac{1}{2} {\mathrm{H}}_2{\mathrm{O}}$. In its formula, $\frac{1}{2} {\mathrm{H}}_2{\mathrm{O}}$ represents water of crystallization.(iii) Washing soda is sodium carbonate decahydrate ${\mathrm{Na}}_2{\mathrm{CO}}_3 \cdot 10 {\mathrm{H}}_2{\mathrm{O}}$ which means it contains 10 water of crystallisation.(iv) Baking soda is sodium bicarbonate $\left( {\mathrm{NaHCO}}_3 \right)$ in anhydrous form without any water of crystallisation.Thus, bleaching powder and baking soda do not have any water of crystallisation.