(i) State the salt and the acid, used in the laboratory preparation of hydrogen chloride.

(ii) Give the equation for the preparation.

(iii) State a method to prove that the gas jar used for collection of HCl gas is filled with hydrogen chloride.

(iv) Observing the method of collection of the gas, state what you can tell about the density of hydrogen chloride.

(i) Salt — Sodium Chloride [NaCl], Acid — Sulphuric acid [H₂SO₄]

(ii) $\text{NaCl} + \text{H}$2\text{SO}4 \xrightarrow{\lt 200 \degree\text{C}} \text{NaHSO}_\text{4} + \text{HCl}

(iii) A glass rod dipped in NH₄OH soln. is brought near the mouth of the gas jar 'Y'. If the gas jar is full with HCl gas then dense white fumes of ammonium chloride are formed.

$\underset{\text{[aq.]}}{\text{NH}$3} + \underset{\text{[vapour]}}{\text{HCl}} \longrightarrow \underset{\text{[dense white fumes]}}{\text{NH}4\text{Cl}}

(iv) This method indicates that HCl gas is heavier than air.