Question

The following questions are pertaining 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

1. The equation for the laboratory preparation of hydrogen chloride gas :

Although it is a reversible reaction, it goes to completion as hydrogen chloride continuously escapes as a gas.

The reaction can occur up to the stage of the formation of sodium sulphate on heating above 200°C. 

2. The drying agent used in the laboratory preparation of hydrochloric acid is conc.sulphuric acid. The other drying agents such as phosphorus pentoxide (P₂O₅ ) and quick lime (CaO) cannot be used because they react with hydrogen chloride. 

3. A safety precaution which should be taken during the preparation of hydrochloric acid : Always wear chemical splash goggles, chemical-resistant gloves and a chemical resistant apron in the laboratory during the preparation of hydrochloric acid.