Question

The following questions pertain to the laboratory preparation of hydrogen chloride gas.

1. Write the equation for its preparation, mentioning the condition required.
   
2. Name the drying agent used in the above preparation and give a reason for the choice.
3. State a safety precaution you would take during the preparation of hydrochloric acid.

Answer 1

(a) Condition: The reaction mixture should be heated below 200°C so that sodium hydrogen sulphate NaHSO₄ is formed. Above 200°C, further reaction occurs to form sodium sulphate.

\[\ce{NaCl + H2SO4 ->[<200^\circ C] NaHSO4 + HCl ^}\]

(b) Drying Agent: Concentrated sulfuric acid (H₂SO₄).

Reason: Concentrated sulfuric acid is an acidic drying agent that efficiently absorbs moisture from the gas without reacting chemically with hydrogen chloride (unlike basic drying agents such as quicklime).

(c) Safety Precaution: Perform the experiment in a fume hood or ensure proper ventilation to avoid inhaling the corrosive and choking HCl fumes, and wear safety goggles and gloves.