Question

Metals like copper fail to evolve hydrogen gas on reacting with dilute nitric acid.

Answer 1

1) Nitric acid(HNO3) is a strong oxidising agent.

2) The Hydrogen gas produced during its reaction with metal gets oxidised to H2O, hence no hydrogen gas is produced.

Instead it evolves nitric oxides such as $N{O}_2,NO$ etc.

3) For Eg:

$Cu\left(s\right)+4HN{O}_3\left(aq\right)⟶Cu\left(N{O}_3{)}_2\right(aq)+2N{O}_2(g)+2H_{2}O(l)$

Sodium aluminate and hydrogen gas are formed,

when sodium hydroxide reacts with aluminium metal.