Hydrogen gas is not evolved when metals like copper, zinc, iron, etc. react with dilute nitiric acid.

Explanation

(i) Nitric acid is a strong oxidizing agent. It oxidizes hydrogen `(H_(2))` to water.
(ii) Hence, it oxidizes complete to form any of the nitrogen and water.
(iii) Hence these metal do not produced `H_(2)` gas when they rect with concentrated and dilute `HNO_(3)`
`underset("Copper")(E.g.Cu_((s)))+underset("Conc. nitric acid")(4HNO_(3(aq))) to underset("Copper nitrate")(Cu(NO_(3))_(2))+underset("Nitrogen dioxide")(2NO_(2(g)))+underset("Water")(2H_(2)O)`