Question

You are given the following materials:

1. Iron nails
2. Copper sulphate solution

Identify the type of chemical reaction taking place when:

Iron nails when left dipped in blue Copper sulphate solution become brownish in colour and the blue colour of the Copper solution fades away.

Answer 1

Displacement reaction:

A reaction in which one element takes the place of another element present in a compound is known as a displacement reaction.

For example:

When Zinc $\left(\mathrm{Zn}\right)$ reacts with Ferrous sulphate $\left({\mathrm{FeSO}}_4\right)$ solution forms Zinc sulphate$\left({\mathrm{ZnSO}}_4\right)$ and Iron $\left(\mathrm{Fe}\right)$.

$\mathrm{Zn}\left(\mathrm{s}\right)+{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+\mathrm{Fe}\left(\mathrm{s}\right)$

The given reaction of Iron nails dipped in Copper sulphate$\left({\mathrm{CuSO}}_4\right)$ solution is an example of a Displacement reaction.

The Copper in the Copper sulphate solution is displaced by Iron$\left(\mathrm{Fe}\right)$. The brownish coating of the Copper is deposited on the surface of Iron nails.

As the concentration of the Copper sulphate solution decreases during the reaction the blue colour of it fades away.

$\mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)\to {\mathrm{FeSO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$