Fe²⁺ ion gets oxidised to Fe³⁺ ion and permanganate ion (MnO₄⁻) gets reduced to Mn²⁺ ion. Fe²⁺ ion acts as reducing agent and MnO₄⁻ ion acts as oxidising agent. The half cell reactions are as follows:
5Fe²⁺ → 5Fe³⁺ + 5e (reaction at anode)
MnO₄⁻ + 8H⁺ + 5e → Mn²⁺ + 4 H₂O (reaction at cathode)
The overall reaction is MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ 4 H₂O.
As per balanced redox reaction 1 mole MnO₄⁻ can oxidise 5 moles of Fe²⁺ ion. So, 0.067 moles of MnO₄⁻ can oxidise 5 X 0.067= 0.335 moles of Fe²⁺ ion.
