Question

Give an example each of the following types of double displacement reaction:

When a change in colour is observed.

Answer 1

1. Double displacement reaction

A double displacement reaction is a chemical reaction that occurs between two compounds and forms distinct compounds by the displacement of ions. It can be represented as:

$\mathrm{AB}+\mathrm{CD}\to \mathrm{AD}+\mathrm{CB}$

2. Example of double displacement reaction

An example of a double displacement reaction in which a colour change is observed is:

$$\begin{gathered} {\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+{\mathrm{FeCl}}_2\left(\mathrm{aq}\right)\to {\mathrm{CuCl}}_2\left(\mathrm{aq}\right)+{\mathrm{FeSO}}_4\left(\mathrm{aq}\right) \\ \mathrm{Copper}\mathrm{Iron}\mathrm{chloride}\mathrm{Copper}\mathrm{Iron}\mathrm{sulphate} \\ \mathrm{sulphate}\mathrm{chloride} \end{gathered}$$

When there is a reaction between Copper sulphate solution and Iron chloride solution, there is an exchange of the ions (sulphate and chloride) from these compounds. This results in the formation of Copper chloride and Iron sulphate. This also changes the colour of the solution from blue to green.

Therefore, it is an example where the change in colour is observed.