Question

The metal which produces hydrogen gas on reaction with dilute hydrochloric acid as well as sodium hydroxide solution is

• A. Copper
• B. Iron
• C. Aluminium
• D. Sodium

Answer 1

The correct option is C

Aluminium

Explanation for correct option:

(C) Aluminium

• When aluminium reacts with dilute hydrochloric acid and sodium hydroxide it liberates hydrogen gas.
• When aluminium reacts with dilute hydrochloric acid it dissolves and forms aluminium chloride and colourless hydrogen gas.

$$\begin{gathered} 2\mathrm{Al}\left(\mathrm{s}\right)+6\mathrm{HCl}\left(\mathrm{aq}\right)\to 2{\mathrm{AlCl}}_3\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right) \\ (\mathrm{Aluminium}\mathrm{metal})(\mathrm{Dilute}\mathrm{hydrochloric}\mathrm{acid})(\mathrm{Aluminium}\mathrm{chlorde})(\mathrm{Hydrogen}\mathrm{gas}) \end{gathered}$$

• Aluminium reacts with sodium hydroxide solution to produce hydrogen gas.
• Aluminium oxide is amphoteric. It acts as an acid with the base, and a base with an acid, neutralizing the other and producing a salt.

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

Hence, this is the correct option.

Explanation for incorrect option:

(A) Copper

• When copper reacts with sodium hydroxide it gives copper hydroxide and with dilute hydrochloric acid no reaction So, it does not produce hydrogen gas. So, this is an incorrect option.

$$\begin{gathered} \mathrm{Cu}\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{aq}\right)\to \mathrm{Cu}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right) \\ \left(\mathrm{Copper}\right)(\mathrm{sodium}\mathrm{hydroxide})(\mathrm{Copper}\mathrm{hydroxide}) \\ \mathrm{Cu}+\mathrm{dil}.\mathrm{HCl}\to \mathrm{no}\mathrm{reaction} \end{gathered}$$

(B) Iron

• Iron does not react and gives hydrogen gas when reacts with sodium hydroxide but with hydrochloric acid. So, this is an incorrect option.

$$\begin{gathered} {\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)\to \mathrm{Fe}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right) \\ \mathrm{Iron}\left(\mathrm{II}\right)\mathrm{Ion}\mathrm{Hydroxide}\mathrm{anion}\mathrm{Iron}\mathrm{hydroxide} \\ \mathrm{Fe}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{FeCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ \mathrm{Iron}\mathrm{Hydrochloric}\mathrm{acid}\mathrm{Iron}\mathrm{chloride}\mathrm{Hydrogen}\mathrm{gas} \end{gathered}$$

(D) Sodium

• The sodium does not form the above products. So, this is an incorrect option.

$$\begin{gathered} \mathrm{Na}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to \mathrm{NaCl}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ \mathrm{Sodium}\mathrm{dil}.\mathrm{Hydrochloric}\mathrm{acid}\mathrm{Sodium}\mathrm{chloride}\mathrm{hydrogen}\mathrm{gas} \end{gathered}$$

Hence, the correct option is (C) Aluminium.