Question

State what happens when : (a) Hydrated copper sulphate is heated (b) Gypusum is heated at 373K. (c) Cholrine gas is passed through dry slaked lime . Also write the chemical equation each case .

Answer 1

b)On heating gypsum at 373 K, it loses water
molecules and becomes calcium sulphate
hemihydrate ( CaSO4. 1/2 H2O). This is called
Plaster of Paris.
c) When chlorine is pased through dry slaked
lime Ca(OH)2 , bleaching powder is obtained .
Ca(OH)2 + Cl2 ---------> CaOCl2 + H2O
Slaked lime Chlorine Bleaching powder

Answer 2

HI !

(a) Hydrated CuSO₄ is heated :-
When CuSO₄.5H₂O ( Hydrated copper sulphate) , contains 5 molecules of water of crystallisation.
Salts containing water of crystallisation are called hydrated salts. When the hydrated salt (CuSO₄.5H₂O ) is heated, it loses its water of crystallisation and becomes anhydrous salts (without water of crystallisation).
The blue colour of CuSO₄ is due to the presence of water of crystallisation. Hence, when it loses its water of crystallisation, the solution becomes colourless.

Equation :-
                              Heat
CuSO₄.5H₂O ------------------------> CuSO₄ + 5H₂O

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(b)  Gypsum is heated at 373 K

Gypsum's formula is CaSO₄.2H₂O  ( Calcium sulphate dihydrate)

When heated,it leads to the formation of plaster of Paris (CaSO₄.1/2H₂O)

The gypsum loses its water of crystallisation,and forms plaster of Paris.
Plaster of Paris is used to plaster fractured bones, to make toys,etc.
By adding water to plaster of Paris , gypsum can be made.


Equation:-

CaSO₄.2H₂O        ------------------------> CaSO₄.1/2H₂O + 3/2H₂O

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(c)Chlorine gas is passed through dry slaked lime

Slaked lime -> Ca(OH)₂

When Chlorine gas is passed through slaked lime , it leads to the formation of bleaching powder(CaOCl₂ - Calcium oxy chloride) .

Ca(OH)₂ + Cl₂ --------------> CaOCl₂ + H₂O