(i) State the special feature of the apparatus used in the laboratory preparation of nitric acid?

(ii) State why the temperature of the reaction mixture of HNO₃ is not allowed to rise above 200°C.

(i) All glass apparatus is used since, the vapours of nitric acid being highly corrosive attack rubber, cork. etc.

(ii) Temperature above 200°C may cause:

1. Damage to the glass apparatus.
2. Further decomposition of nitric acid
3. Formation of hard residual crust of the corresponding sulphate [Na₂SO₄ or K₂SO₄] which being a poor conductor of heat, sticks to the glass and cannot be easily removed from the apparatus.