Question

Which gas is usually liberated when an acid reacts with a metal ?

Answer 1

'Hydrogen gas' is liberated when an acid reacts with a metal.

For example, Zinc reacts with dilute sulphuric acid to form zinc sulphate along with the evolution of hydrogen gas.

$Zn+H_{2}S{O}_4\to ZnS{O}_4+H_2$

Hydrogen ignites with a 'pop' sound when placed near a glowing splint (test for hydrogen gas).