Question

hydrogen gas is not evolved when a metal reacts with nitric acid. justify​

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)  

i hope it will helps you friend

Answer 2

When metals react with nitric acid hydrogen gas is liberated.

Nitric acid is a very strong oxidizing agent.

So , it oxidizes the hydrogen gas formed during the reaction to form water and an oxide of nitrogen (NO,N2O,NO2 etc.).

The reaction for it is:-

Zn+4HNO3→Zn(NO3)2+2NO2+2H2O

Exception:-

Magnesium and manganese react with very dilute nitric acid to liberate hydrogen gas.

The reaction for it is:-

Mg+2HNO3→Mg(NO3)2+H2