Question

a) Write the chemical formula of hydrated copper sulphate and anhydrous copper sulphate. Giving an activity illustrate how these two are inter convertible.
(b) Write chemical names and formulae of plaster of paris and gypsom.


CBSE Class X Science LA (5 Marks)

Answer 1

(a) Hydrated copper sulphate – CuSO4.5H2O Anhydrous copper sulphate – CuSO4. Activity :

(i) Heat a few crystals of copper sulphate in a dry boiling tube.
 
(ii) Add 2-3 drops of water on the sample of copper sulphate obtained after heating. After heating, water is removed and salt turns white. If crystal are moisten again with water, blue colour reappears. Water of crystallization is fixed number of water molecules present in one formulae unit of a salt. Five water molecules are present in one formula unit of copper sulphate.
 
(b) Calcium sulphate hemihydrate – CaSO4. H2O Calcium sulphate dihydrate – CaSO4.2H2O.

Answer 2

A) The chemical formula of hydrated copper sulphate is Custom. 5H2O

And of An hydrostatic copper sulphate is CUSO4.

1) The blue copper solution contain copper sulphate and 5 molecules of water. Hence it is known as water of crystallization.

2)Heat a few crystals of copper sulphate in a beaker.

3)On heating CuSO4. 5h2O hydrated solution, water of crystallization is looses due to evaporation thus CuSO4 tend to lose its colour and shape, leaving behind An hydrostatic copper sulphate acidic salt in form of white precipitate powder. Therefore, we get white crystal of unhydrous copper sulphate on heating.

4)We can get its original form by adding more water into it.

B) gypsum:- CUSO4. 2H20

(Calcium sulphate dihydrate)

Plaster of Paris (POP) :- CUSO4.1/2H20 + 1.5H20