Question

Name a metal which reacts with very dilute nitric acid to liberate hydrogen.

Answer 1

1. Nitric acid (${\mathbf{HNO}}_{\mathbf{3}}$) in its concentrated form is considered as a strong oxidising agent as a result it oxidises hydrogen immediately to form water.
2. But dilute Nitric acid (${\mathbf{HNO}}_{\mathbf{3}}$) on reacting with Magnesium ($\mathbf{Mg}$) metal gives Hydrogen (${\mathbf{H}}_{\mathbf{2}}$).
3. The reaction is shown below.
   $$\begin{gathered} \mathrm{Mg}\left(\mathrm{s}\right)+2{\mathrm{HNO}}_3\left(\mathrm{aq}\right)\to \mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ \mathrm{Magnesium}\mathrm{Nitric}\mathrm{Magnesium}\mathrm{Hydrogen} \\ \mathrm{acid}\mathrm{nitrate} \end{gathered}$$
4. In the given reaction, Magnesium ($\mathbf{Mg}$) reacts with a dilute solution of Nitric acid (${\mathbf{HNO}}_{\mathbf{3}}$) to give Magnesium nitrate ($\mathbf{Mg}{\mathbf{\left(}{\mathbf{NO}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{2}}$) and Hydrogen (${\mathbf{H}}_{\mathbf{2}}$) as a product.
5. Therefore, a metal which reacts with very dilute Nitric acid (${\mathbf{HNO}}_{\mathbf{3}}$) to liberate hydrogen (${\mathbf{H}}_{\mathbf{2}}$) is Magnesium (Mg).