A dilute ferrous sulphate solution is gradually

Question:

A dilute ferrous sulphate solution is 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) KMnO4 is an oxidising agent and it oxidises FeSO4

(b) FeSO4 acts as an oxidising agent and it oxidises KMnO4

(c) The colour disappears due to dilution; no reaction is involved

(d) KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound.

Solution:

(a). Potassium permanganate (KMnO4) is an oxidising agent. It oxidises ferrous sulphate to ferric sulphate in the presence of dilute

H2SO4.

$2 \mathrm{KMnO}_{4}+8 \mathrm{H}_{2} \mathrm{SO}_{4}+10 \mathrm{FeSO}_{4}$

(Purple)

$\longrightarrow \mathrm{K}_{2} \mathrm{SO}_{4}+2 \mathrm{MnSO}_{4^{+}} 8 \mathrm{H}_{2} \mathrm{O}+5 \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}$

By taking part in the reaction, the light purple colour of the solution slowly fades and finally disappears.

 

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