Question

The reaction of zinc metal and HCl produces which of the following?
(i). ${{\text{H}}_{\text{2}}}{\text{(g)}}$
(ii). ${\text{C}}{{\text{l}}_{\text{2}}}{\text{(g)}}$
(iii). ${\text{ZnC}}{{\text{l}}_{\text{2}}}{\text{(aq)}}$

Answer 1

To answer this question we should have some idea of electrochemical series. So, we decide whether the given metal can release the hydrogen or not. The species having less reduction potential then the reduction potential of hydrogen can release hydrogen gas. The reduction potential is determined by electrochemical series.

Complete solution:
The series of elements arranged according to their reduction potential is known as electrochemical series. The ease of reduction of an element is determined by its reduction potential.
The reduction potential of hydrogen is $0\,{\text{v}}$ and the reduction potential of zinc is $- 0.76\,{\text{v}}$.
Metal with low reduction potential gets oxidised easily and releases hydrogen gas.
So, as the reduction potential of zinc is less so, zinc will reduce and hydrogen will oxidize so, the zinc can release hydrogen gas on reacting with hydrochloric acid.
The reaction is shown as follows:
${\text{Zn + }}2\,\,{\text{HCl}}\, \to \,{\text{ZnC}}{{\text{l}}_2}\, + \,{{\text{H}}_{\text{2}}}{\text{(g)}}$
So, the reaction of zinc metal and HCl produces ${{\text{H}}_{\text{2}}}{\text{(g)}}$ and ${\text{ZnC}}{{\text{l}}_{\text{2}}}{\text{(aq)}}$.

Therefore, the correct answer is (D).

Note: The species which donate electrons is known as oxidised and the process is known as oxidation. The opposite process in which the species gain electrons is known as reduction. The hydrogen lies in between the series. The elements having high reduction potential then hydrogen will get reduced and cause the oxidation of hydrogen or acid. So, they cannot release hydrogen gas.
The elements having low reduction potential then hydrogen will get oxidized and cause the reduction of hydrogen or acid and release the hydrogen as hydrogen gas.