Question

Why does nitric oxide do not liberate H2 gas when react with metal ??

Answer 1

Dear student,
Nitric acid(HNO3) is a strong oxidizing agent.
The Hydrogen gas produced during its reaction with metal gets oxidized to H2O, hence no hydrogen gas is produced.
Instead, it evolves nitric oxides such as NO2, NO etc.

For Eg:
Cu(s) + 4HNO3(aq)--->Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)