Give reasons for the following — pertaining to the above laboratory preparation of nitric acid
(i) concentrated hydrochloric acid is not used as a reactant in the laboratory preparation.
(ii) the complete apparatus in the laboratory preparation does not contain parts made of rubber or cork.
(iii) the reaction temperature is maintained below 200°C
(iv) at high temperatures the sodium sulphate or potassium sulphate formed, forms a crust and sticks to the glass apparatus.

Question

Give reasons for the following — pertaining to the above laboratory preparation of nitric acid
(i) concentrated hydrochloric acid is not used as a reactant in the laboratory preparation.
(ii) the complete apparatus in the laboratory preparation does not contain parts made of rubber or cork.
(iii) the reaction temperature is maintained below 200°C
(iv) at high temperatures the sodium sulphate or potassium sulphate formed, forms a crust and sticks to the glass apparatus.

KnowledgeBoat · Accepted Answer

(i) Conc. HCl is not used in place of conc. sulphuric acid, since being volatile itself it is not used to displace another volatile acid. (ii) All glass apparatus is used in the laboratory preparation of nitric acid since the vapours of nitric acid being highly corrosive attack rubber, cork, etc. (iii) High temperatures above 200°C are not used as they may cause : 1. Damage to the glass apparatus. 2. Further decomposition of nitric acid. 3. Formation of a hard residual crust of the corresponding sulphate [Na₂SO₄ and K₂SO₄] which being a poor conductor of heat, sticks to the glass and cannot be easily removed from the apparatus. (iv) At high temperatures above 200°C, a hard residual crust of the corresponding sulphate [Na₂SO₄ and K₂SO₄] is formed which being a poor conductor of heat, sticks to the glass and cannot be easily removed from the apparatus.

Chemistry

Nitric Acid

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