Question

why is h2 gas not evolved when a metal is heated with nitric acid?

Answer 1

Nitric acid(HNO3) is a strong oxidising agent.
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  NO2,NO etc.

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

Answer 2

hey dear
here is your answer ☞

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⭐ H2 gas is not evolved when a metal is heated with nitric acid because it acts as a strong oxidising agent. it oxidises H2 to become H2O. ⭐

hope it helps ^_^