Hydrogen chloride gas is prepared in the laboratory using conc. H₂SO₄ and NaCl. Answer the questions that follow based on this reaction.

(i) Give the balanced chemical equation for the reaction with suitable condition[s] if any.

(ii) Why is concentrated sulphuric acid used instead of conc. nitric acid.

(iii) How is the gas collected.

(iv) Name the drying agent not used for drying the gas.

(i) Balanced chemical equation for the reaction are :

$\text{NaCl} + \text{H}$2\text{SO}4 \xrightarrow{\lt 200 \degree\text{C}} \text{NaHSO}_4 + \text{HCl [g.]}

(ii) 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.
Conc. nitric acid cannot be used in place of conc. H₂SO₄ since it is volatile and may volatize out along with the hydrogen chloride.

(iii) The gas is collected by upward displacement of air method.

(iv) Quicklime (CaO) and phosphorous pentoxide [P₂O₅] are not used as drying agent, since they react with HCl forming their respective chlorides.