The number of moles of KMnO₄ that are needed to react completely with one mole of ferrous oxalate in acidic solution is

3KMnO₄ + 5FeC₂O₄ + 24H⁺ $\to$ 3Mn²⁺ + 5Fe³⁺ + 10CO₂ +12H₂O

KMnO₄ = 5 electrons

ferrous oxalate in acidic solution = 3 electrons

while reaction exchange of electrons takes place..........so

3 moles of KMnO₄ = 5 moles of FeC₂O₄

5 moles of FeC₂O4 = 3 moles of KMnO₄

so 1 mole of FeC₂O₄ = 3/5 moles of KMnO₄

hence 3/5=0.6 moles of KMnO₄ will be needed to react completely with one mole of ferrous oxalate in acidic solution.....