Question

What happens when zinc granules are added to hydrochloric acid?

Answer 1

Zinc is a metal and so it shows the properties of metals. Metals are known to take part in oxidation and reduction reactions when treated with appropriate reagents.

Complete step by step answer:
Zinc is an element in the periodic table with atomic number $30$. It electronic configuration is
$Zn:1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}3{d^{10}}4{s^2}$
The outermost shell of zinc is $4$ which contains two electrons in the $4s$ shell. It has the tendency to lose both electrons and attain a $+ 2$ oxidation state. Thus zinc undergoes oxidation to form $Z{n^{2 + }}$, by losing electrons.
Hydrochloric acid as the name suggests is an acid. Acids are known to donate protons and accept electrons. The hydrochloric acid also donates the proton and accepts electrons from any metal on treatment with.
In this case the reaction between zinc and hydrochloric acid is shown as
$Zn + 2HCl \to ZnC{l_2} + {H_2} \uparrow$
This is an example of a single replacement reaction where zinc metal displaces the hydrogen to form zinc chloride and hydrogen gas. The reaction is very rapid and vigorous in which the zinc metal reacts quickly with the acid to form bubbles of hydrogen.
The oxidation state of zinc in zinc granules is zero. The oxidation state of zinc in $ZnC{l_2}$ is $+ 2$. Thus zinc undergoes oxidation to produce $Z{n^{2 + }}$ with loss of electrons. The electrons are taken by hydrochloric acid to produce hydrogen gas.
Thus a single replacement reaction will occur when zinc granules are added to hydrochloric acid in which oxidation and reduction takes place with the starting materials.

Note:
Zinc undergoes a similar reaction on treatment with dilute sulphuric acid. Other metals like tin and iron also take part in such kinds of replacement reactions.