Question

Hydrogen gas is not evolved when metals react with_______.

Answer 1

Evolution of hydrogen gas:

• Hydrogen gas is not evolved when there is a reaction between metal and Nitric acid $\left({\mathrm{HNO}}_3\right)$occurs as Nitric acid is a strong oxidizing agent.
• The Hydrogen gas produced during the reaction with metal gets oxidized to ${\mathrm{H}}_2\mathrm{O}$, hence no hydrogen gas is produced.
• Instead, it evolves nitric oxides such as ${\mathrm{NO}}_2,\mathrm{NO}$ etc.
• Example: When a Silver metal reacts with Nitric acid $\left({\mathrm{HNO}}_3\right)$to give ${\mathrm{N}}_2\mathrm{O}\mathrm{and}{\mathrm{H}}_2\mathrm{O}$.

$\underset{\left(\mathrm{Silver}\right)}{\mathrm{Ag}\left(\mathrm{s}\right)}+\underset{(\mathrm{Nitric}\mathrm{acid})}{2{\mathrm{HNO}}_3\left(\mathrm{l}\right)}\to \underset{(\mathrm{Silver}\mathrm{nitrate})}{{\mathrm{AgNO}}_3(\mathrm{s}})+\underset{(\mathrm{Nitrogen}\mathrm{dioxide})}{{\mathrm{NO}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

Hence, hydrogen gas is not evolved when metals react with Nitric acid.