Amount of substance of $\ce{MnO4-}$ required to oxidize one mole of ferrous oxalate completely in acid medium will be:
(a) 7.5 moles
(b) 0.2 moles
(c) 0.6 moles
(d) 0.4 moles
In acidic medium, 1 mole of $\ce{MnO_4^-}$ accepts 5 moles of electrons. Oxalate is dibasic so will give 2 moles of electrons when oxidized to $\ce{CO2}$.
$\ce{Fe^2+ -> Fe^3+ + e-} $ so total 3 moles of electrons.
$\text{Amount of substance of } \ce{MnO_4^-}=\frac{3}{5}=0.6$
However, the given answer is 0.4 moles indicating that only oxalate is considered to be oxidized.
Does $\ce{Fe^{2+} -> Fe^{3+} + e^-} $ actually occur in this reaction?
What would be the net reaction when $\ce{KMnO_4}$ is used(not just the ions)?