Question

Describe an experiment to prove the following:
(i) HCl gas is heavier than air.
(ii) HCl gas is highly soluble in water.
(iii) HCl gas contains the element chlorine.

Answer 1

(i) Experiment to prove that HCl gas is heavier than air:

Procedure	Observation	Conclusion
Fill two jars A and B with air and HCl gas, respectively. Invert the jar containing HCl gas over the jar containing air. After some time, separate the jars and bring a glass rod dipped in ammonium hydroxide solution inside jar A.	Dense white fumes of ammonium chloride	HCl gas displaces the air from the jar as it is heavier than air.

(ii) Experiment to prove that HCl gas is highly soluble in water:

Procedure	Observation	Conclusion
Fill dry HCl gas in a round-bottomed flask. Close the openings of the flask with rubber corks. Insert a jet tube through one of the holes. Through the second hole, insert a dropper filled with water. Close the open end of the jet tube and dip it in a blue litmus solution. Invert the flask and press the dropper.	The blue litmus solution enters the jet tube and forms a red fountain.	HCl gas is highly soluble in water.

(iii) Experiment to prove that HCl gas contains chlorine:

Hydrogen chloride reacts with strong oxidising agents (like MnO₂, Pb₃O₄ , etc.) to release chlorine gas, which is greenish yellow in colour with a pungent smell.

Release of chlorine gas:
MnO₂(s) + 4HCl(aq) → MnCl₂(aq) + 2H₂O(l) + Cl₂(g)