Question

Which of the following metals on reacting with Sodium Hydroxide solution produce Hydrogen Gas?

• A. Iron$\left(\mathrm{Fe}\right)$
• B. Zinc$\left(\mathrm{Zn}\right)$
• C. Aluminum$\left(\mathrm{Al}\right)$
• D. Both B and C

Answer 1

The correct option is D

Both B and C

Explanation for correct option:

D. Both B and C

Reaction of metal with Sodium hydroxide:

• When a metal reacts with a base, a salt is formed along with the liberation of hydrogen gas.
• When Zinc$\left(\mathrm{Zn}\right)$ reacts with sodium hydroxide$\left(\mathrm{NaOH}\right)$ solution, Sodium zincate$\left({\mathrm{Na}}_2{\mathrm{ZnO}}_2\right)$ is formed along with the liberation of hydrogen$\left({\mathrm{H}}_2\right)$ gas.
• The chemical reaction can be depicted as:

$$\begin{gathered} \mathrm{Zn}\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{aq}\right)\to {\mathrm{Na}}_2{\mathrm{ZnO}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ \left(\mathrm{Zinc}\right)(\mathrm{Sodium}\mathrm{hydroxide})(\mathrm{Sodium}\mathrm{zincate})\left(\mathrm{Hydrogen}\right) \end{gathered}$$

• When Aluminium$\left(\mathrm{Al}\right)$ reacts with sodium hydroxide$\left(\mathrm{NaOH}\right)$ solution in presence of water, Sodium aluminate$\left({\mathrm{NaAlO}}_2\right)$ is formed along with the liberation of hydrogen$\left({\mathrm{H}}_2\right)$ gas.
• The chemical reaction can be depicted as:

$$\begin{gathered} 2\mathrm{Al}\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2{\mathrm{NaAlO}}_2\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right) \\ \left(\mathrm{Aluminium}\right)(\mathrm{Sodium}\mathrm{hydroxide})\left(\mathrm{Water}\right)(\mathrm{Sodium}\mathrm{aluminate})\left(\mathrm{Hydrogen}\right) \end{gathered}$$

Explanation for incorrect options:

A. Reaction of iron with sodium hydroxide:

• When Iron$\left({\mathrm{Fe}}^{2+}\right)$ salts react with sodium hydroxide$\left(\mathrm{NaOH}\right)$ solution, a green-colored precipitate is formed that is insoluble in excess sodium hydroxide solution.
• The chemical reaction can be depicted as:

$$\begin{gathered} {\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)+\mathrm{NaOH}\left(\mathrm{aq}\right)\to \mathrm{Fe}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right) \\ (\mathrm{Ferric}\mathrm{ion})(\mathrm{Sodium}\mathrm{hydroxide})(\mathrm{Ferric}\mathrm{hydroxide}) \end{gathered}$$

Thus, the correct option is D i.e. Both B and C. Both Zinc and Aluminium react with sodium hydroxide to produce Hydrogen gas.