How many moles of ${\mathrm{KMnO}}_4$ are required to oxidise 10 moles of ferrous oxalate in acidic medium. 

In acidic medium, ${\mathrm{MnO}}_4^{-}$ oxidizes ferrous ion into ferric ion. The balanced chemical reaction is:

$3{\mathrm{MnO}}_4^{-}+5{\mathrm{FeC}}_2{\mathrm{O}}_4+24{\mathrm{H}}^{+}⟶5{\mathrm{Fe}}^{+3}+10{\mathrm{CO}}_2+3{\mathrm{Mn}}^{+2}+12{\mathrm{H}}_2\mathrm{O}$

If 5 moles of ferrous oxalate are oxidized by 3 moles of KMnO₄, then 10 moles of ferrous oxalate required 6 moles of KMnO₄.