Question

Why hydrogen not liberated when metals react with nitric acid

Answer 1

Nitric Acid is a highly oxidising agent.

Whenever a metal reacts with HNO3, it doesn't liberate Hydrogen Gas because The hydrogen gas produced in the process is oxidised by Nitric Acid.

And,

The Nitric Acid itself gets reduced to any of the Nitrogen oxide like Nitric oxide, Nitrous oxide, Nitrogen dioxide after oxidising the Hydrogen gas produced.

But very few metals produce Hydrogen gas after reacting with very very dilute Nitric Acid.

But,

In most of the cases, the Hydrogen gas is not liberated as it gets oxidised to Water due to the oxidising Agent that is Nitric Acid.

Nitric Acid itself undergoes Reduction.