Hydrogen gas is not evolved when a metal reacts with nitric acid because nitric acid is a strong oxidizing agent; it oxidizes the hydrogen to produce water.
- When a metal reacts with nitric acid, no hydrogen gas is produced. It’s because HNO3 is a strong oxidizer.
- It reduces itself to any of the nitrogen oxides (N2O, NO, NO2) after oxidizing the H2 released to water.
- Magnesium (Mg) and manganese (Mn), on the other hand, react with very dilute HNO3 to produce H2 gas.