Question

When a solution of ferrous sulphate (${\mathrm{FeSO}}_4$) is added to an acidified purple solution of potassium permanganate (${\mathrm{KMnO}}_4$). The purple colour fades and finally disappears. Which one of the following statements is correct?

• A. The colour disappears because of dilution and no reaction occurs.
• B. Potassium permanganate oxidizes ferrous sulphate and itself is reduced
• C. Ferrous sulphate is an oxidizing agent and it oxidizes ${\mathrm{KMnO}}_4$
• D. ${\mathrm{KMnO}}_4$, is a reducing agent and it reduces ${\mathrm{FeSO}}_4$.

Answer 1

The correct option is B

Potassium permanganate oxidizes ferrous sulphate and itself is reduced

Explanation for correct option

Option B)

The substance which undergoes reduction is the oxidising agent. It accepts electrons.

The reaction when a solution of Ferrous sulphate (${\mathrm{FeSO}}_4$) is added to an acidified solution of Potassium permanganate (${\mathrm{KMnO}}_4$) is as shown below:

$$\begin{gathered} 2{\mathrm{KMnO}}_4\left(\mathrm{aq}\right)+10{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)+8{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{K}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+2{\mathrm{MnSO}}_4\left(\mathrm{s}\right)+5{\mathrm{Fe}}_2{\left({\mathrm{SO}}_4\right)}_3\left(\mathrm{aq}\right)+8{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right) \\ (\mathrm{Potassium}(\mathrm{Ferrous}(\mathrm{Sulfuric}(\mathrm{Potassium}\left(\mathrm{Manganese}\right(\mathrm{II})(\mathrm{Iron}\left(\mathrm{III}\right)\left(\mathrm{Water}\right) \\ \mathrm{manganate}\left(\mathrm{VII}\right))\mathrm{sulphate})\mathrm{acid})\mathrm{sulphate})\mathrm{sulphate})\mathrm{sulphate}) \end{gathered}$$

Here, ${\mathrm{KMnO}}_4$ is an oxidizing agent. It oxidises ${\mathrm{FeSO}}_4$ to ${\mathrm{Fe}}_2{\left({\mathrm{SO}}_4\right)}_3$ in the presence of acid and it undergoes reduction.

Explanation for the incorrect options

Option A) A redox chemical reaction takes place.

Option C) Iron in Ferrous sulphate undergoes oxidation, so it is a reducing agent.

Option D) In Potassium permanganat, Manganese (Mn) undergoes reduction, so it is an oxidising agent.

Option (B) is correct., Potassium permanganate oxidises Ferrous sulphate and that itself is reduced.