Question

What do you observe from the following chemical reaction:
$Zn{\text{ + 2HCl(dil}}{\text{.) }}\xrightarrow{{}}{\text{ ZnC}}{{\text{l}}_2}{\text{(aq}}{\text{.) + }}{{\text{H}}_2}{\text{(g)}}$

Answer 1

In the given reaction zinc granules are reacted with the dilute solution of hydrochloric acid which produces an aqueous solution of zinc chloride and also there is an evolution of hydrogen gas. It is one of the types of reaction in which an element displaces another element.

Complete answer:
The zinc particles or we can say zinc granules are added to react with dilute solution of hydrochloric acid to form an aqueous solution of Zinc Chloride as main product and also evolve hydrogen gas as a by-product of the reaction. We can clearly observe that zinc atoms displace the hydrogen atom from hydrochloric acid and make an aqueous solution of Zinc Chloride. Therefore, it displaces the other element; we can call it a displacement reaction. Since there is a displacement of only one element we can call it a single-displacement reaction. In addition to that, there is also an evolution of hydrogen gas which is the by-product of the reaction. We can check the evolution of hydrogen gas by bringing a burning candle near it. The candle will be blown up if hydrogen gas is evolved during reaction. Also this is a balanced chemical equation in which the atomicity of atoms at reactants is equal to atomicity of atoms at products. Also there is change in oxidation state of the elements. Therefore it can be called a redox reaction.

Note:
For redox reactions, the oxidation and reduction should take place in that reaction. Here Zinc is being oxidised while hydrogen gets reduced. Thus we regard it as a redox reaction. We can also check the evolution of hydrogen gas with the help of other methods too.