Explain the following observations :

(i) Washing-soda become coated with a white powder when left exposed to the atmosphere.

(ii) In the expression anhydrous copper sulphate, what is meant by 'anhydrous'.

(iii) Why is fused calcium chloride or conc. sulphuric acid used in a desiccator.

(i) Washing Soda is an efflorescent substance and so when it is exposed to the atmosphere, it loses it's moisture [water of crystallization] partly and changes into amorphous state. Hence, a white powder forms on the surface of washing soda crystals which are left exposed to the air.

(ii) When copper sulphate loses water of crystallization on being heated, it becomes white powder of CuSO₄ and is called anhydrous copper sulphate.

(iii) Fused calcium chloride or conc. sulphuric acid is deliquescent in nature, absorbs moisture and hence used as drying agent or desiccating agent.