The number of moles of ${\mathrm{MnO}}_4^{-}$ and ${\mathrm{Cr}}_2{\mathrm{O}}_7^{-2}$ separately required to oxidise 1 mole of ${\mathrm{FeC}}_2{\mathrm{O}}_4$ each in acidic medium respectively.

${\text{3MnO}}_{\text{4}}^{\text{-}}{\text{\hspace{0.17em}+\hspace{0.17em}5FeC}}_{\text{2}}{\text{O}}_{\text{4}}\text{+\hspace{0.17em}}{\text{24H}}^{\text{+}}\stackrel{ }{\to }$
${\text{3Mn}}^{\text{+2}}{\text{\hspace{0.17em}+5Fe}}^{\text{+3}}{\text{+\hspace{0.17em}10CO}}_2{\text{\hspace{0.17em}+\hspace{0.17em}12H}}_{\text{2}}\text{O}$
$3\text{moles}\stackrel{ }{\leftarrow }5\text{moles}$
$\stackrel{ }{? \left(x\right) \stackrel{ }{\leftarrow }1mole}$
$\text{x\hspace{0.17em}=\hspace{0.17em}}\frac{\text{3}}{\text{5}}{\text{\hspace{0.17em}moles\hspace{0.17em}\hspace{0.17em}=\hspace{0.17em}0.6\hspace{0.17em}\hspace{0.17em}moles\hspace{0.17em}\hspace{0.17em}of\hspace{0.17em}\hspace{0.17em}MnO}}_{\text{4}}^{\text{-}}$
${\text{Cr}}_{\text{2}}{\text{O}}_{\text{7}}^{\text{-2}}{\text{\hspace{0.17em}+\hspace{0.17em}2FeC}}_{\text{2}}{\text{O}}_{\text{4}}\text{\hspace{0.17em}+\hspace{0.17em}}{\text{14H}}^{\text{+}}\stackrel{ }{\to }$
${\text{2Cr}}^{\text{+3}}{\text{\hspace{0.17em}+\hspace{0.17em}2Fe}}^{\text{+3}}{\text{\hspace{0.17em}+\hspace{0.17em}4CO}}_{\text{2}}{\text{\hspace{0.17em}+\hspace{0.17em}7H}}_{\text{2}}\text{O}$
$1 mole \stackrel{ }{\leftarrow } 2moles$
$? \left(x\right) \stackrel{ }{\leftarrow } 1 moles$
$\text{x\hspace{0.17em}=\hspace{0.17em}}\frac{\text{1}}{\text{2}}{\text{\hspace{0.17em}=\hspace{0.17em}0.5\hspace{0.17em}moles\hspace{0.17em}\hspace{0.17em}of\hspace{0.17em}\hspace{0.17em}Cr}}_{\text{2}}{\text{O}}_{\text{7}}^{\text{-2}}$