Question

Answer the questions below, relating your answers only to salts in the following list:
sodium chloride, anhydrous calcium chloride, copper sulphate-5-water.
(i) What is the name given to the water in the compound copper sulphate-5-water?
(ii) If copper sulphate-5-water is heated, the water is driven off leaving anhydrous copper sulphate. What is the colour of anhydrous copper sulphate?
(iii) By what means, other than heating, can you dehydrate copper sulphate-5-water and obtain anhydrous copper sulphate?
(iv) Which one of the salts in the given list is deliquescent?

Answer 1

(i) Water of crystallisation is the name given to the water present in the compound copper sulphate-5-water (${\mathrm{CuSO}}_4.5{\mathrm{H}}_2\mathrm{O}$)​.

(ii) The colour of anhydrous copper sulphate is white.

(iii) By efflorescence, we can dehydrate copper sulphate-5-water and obtain anhydrous copper sulphate. Efflorescence is the loss of water of crystallisation by a hydrated salt when it comes in contact with dry air. The hydrated salt gets crushed to powder in the process.
Also, copper sulphate-5-water loses its water of crystallisation on treatment with a dehydrating agent like concentrated sulphuric acid.

(iv) Anhydrous calcium chloride is deliquescent in nature.