Question

6. A dilute ferrous sulphate solution was gradually added to the
beaker containing acidified permanganate solution. The light
purple colour of the solution fades and finally disappears.
Which of the following is the correct explanation for the
observation?
(a) KMnO, is an oxidising agent, it oxidises Feso,
(b) FeSo, acts as an oxidising agent and oxidises KMnO,
(c) The colour disappears due to dilution; no reaction is involved
(d) KMnO, is an unstable compound and decomposes in presence
of Feso, to a colourless compound.​

Answer 1

Answer:

Correct option ( b )

Explanation:

A permanganate solution is usually purple in colour. Permanganate contains the manganate ion (MnO₄⁻) and manganese has an OS of +7. However, in an acidic solution, the permanganate (VII) ion gets reduced to the manganese (Mn₂⁺) ion which has an oxidation state of +2 and is colourless.

Since Potassium permanganate (KMnO₄) is quite an unstable compound, it tends to decompose in the presence of Ferrous sulphate (FeSO₄). This changes the colour of the solution from purple to colourless. The FeSO₄ gets oxidized to Fe₂(SO₄)₃ as KMnO₄ acts as a good oxidizing agent in an acidic medium.