Question

Q. Generally when metals are treated with mineral acids hydrogen gas liberated but when metals (except Mn and Mg) are treated with HNO3 hydrogen is not liberated. why?

Answer 1

HNO3 is a very strong oxidising agent, (it has a very strong liking for Hydrogen and doesn't want it to stay alone). As soon as Hydrogen is formed, HNO3 helps in oxidising it into water.

Answer 2

It is beacuse HNO3 is a strong oxidising agent it oxidies the H2 produced to H2O and iteself get reduced to any of the oxides of the nitrogen like No2,No etc