Question

How will you test for the gas which is liberated when hydrochloric acid reacts with an active metal?

Answer 1

Identification of the gas:
Hydrogen gas is evolved when hydrochloric acid reacts with an active metal such as sodium, potassium, calcium or magnesium.

Example-$\text{Mg(s)}+2\text{HCl(aq)}\to {\text{MgCl}}_2\text{(aq)}+{\text{H}}_2\text{(g)}$
Test:
In order to test the gas, pass it through soap solution. Gas-filled bubbles are formed. Also, when a burning matchstick is brought near these bubbles, the bubbles burn with a pop sound.