Each Part: 2.5 Marks
The reaction of nitric acid is different for different metals. Concentrated nitric acid evolves NO2, while dilute nitric acid evolves NO on reaction with metals.
For example,
Zn+4HNO3(conc.)→Zn(NO3)2+2H2O+2NO2↑
3Zn+8HNO3(dil.)→3Zn(NO3)2+4H2O+2NO↑
In the case of reaction of nitric acid with metals, hydrogen gas is not liberated due to the fact that nitric acid not only behaves as an intermediate product which reduces nitric acid as an oxidising agent but nascent hydrogen is formed as an intermediate product which reduces nitric acid to products like NO2, NO, H2O.