In the laboratory preparation of HCl from sodium chloride, state why the following are preferred –

(i) Conc. H₂SO₄ as a reactant

(ii) Temp. below 200°C

(iii) Conc. H₂SO₄ as a drying agent.

(i) As conc. H₂SO₄ is non-volatile and has a high boiling point, therefore, it displaces the volatile hydrogen chloride from the salt sodium chloride. Hence, conc. H₂SO₄ is used as a reactant in the laboratory preparation of HCl from sodium chloride

(ii) The fuel is not wasted, the glass apparatus does not crack and sodium sulphate does not form hard crust, which in turn may stick to the glass and will be difficult to remove. Therefore, temperature below 200°C is used.

(iii) Drying agent used for drying should only remove the moisture and not react with it, hence, conc. sulphuric acid is used as the drying agent.