Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?
The reaction of Acids and Metal leads to the formation of a salt. Hydrogen being common to all acids gets displaced in the reaction and is evolved as hydrogen gas.
Acid + Metals → Salt + Hydrogen Gas
For Example : When Zinc (Zn) reacts with dilute Sulphuric Acid (H 2 SO 4 ) , it produces a salt called Zinc Sulphate (ZnSO 4 ) and Hydrogen Gas.
Zn(s) + H 2 SO 4 (aq) → ZnSO 4 (aq) + H 2 (g)
The characteristic of Hydrogen gas is that it burns with a pop sound.Hence, to check the presence of H 2 gas, bring the flame of a burning candle near the mouth of the container where the reaction is taking place. If a pop sound is heard, then the presence of H 2 gas is confirmed.