Answer:
Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because
HNO
3
is a strong oxidizing agent. It oxidizes the
H
2
to water and itself gets reduced to any of the nitrogen oxides
N
2
O
,
NO
,
NO
2
. But magnesium
(
Mg
)
and manganese
(
Mn
)
react with very dilute
HNO
3
to evolve
H
2
gas.