Name the gas which is liberated when an acid reacts with a metal. Illustrate with an example. How will you test the presence of this gas?

(N/A) When an acid reacts with a metal,$Hydrogen$ gas is liberated.
Example: When $Zinc$ granules react with dilute $Hydrochloric$ acid $(HCl)$,$Zinc$ chloride $(ZnCl_{2})$ and $Hydrogen$ gas $(H_{2})$ are produced.
$Zn(s) + 2HCl(aq) \longrightarrow ZnCl_{2}(aq) + H_{2}(g)$
Test for $Hydrogen$ gas: Bring a burning candle or a matchstick near the mouth of the test tube containing the gas. The gas burns with a characteristic '$pop$' sound,which confirms the presence of $Hydrogen$ gas.