(a) Explain why metals usually do not liberate hydrogen gas with dilute nitric acid.
(b) Name two metals which can, however, liberate hydrogen gas from very dilute nitric acid.
(a)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.
(b)Magnesium and Manganese can generate H2 with very dilute HNO3 because at very low concentration HNO3 can not oxidise H2 to water