For the redox reaction
$\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}+{\mathrm{C}}_2{\mathrm{O}}_4^{2-}+{\mathrm{H}}^{+}\to \mathrm{M}{\mathrm{n}}^{2+}+\mathrm{C}{\mathrm{O}}_2+{\mathrm{H}}_2\mathrm{O}$
The correct coefficients of the reactants for the balanced equation are
$\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}$ ${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$ ${\mathrm{H}}^{+}$

• A

  $\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}$	${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$	${\mathrm{H}}^{+}$
  2	16	5

• Correct answer
  B

  $\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}$	${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$	${\mathrm{H}}^{+}$
  2	5	16

• C

  $\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}$	${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$	${\mathrm{H}}^{+}$
  16	5	2

• D

  $\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}$	${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$	${\mathrm{H}}^{+}$
  5	16	2

Solution

n-factor of $\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}\Rightarrow 5$
n-factor of ${\mathrm{C}}_2{\mathrm{O}}_4^{2-}\Rightarrow 2$
Ratio of n-factors of $\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}$ and ${\mathrm{C}}_2{\mathrm{O}}_4^{2-}$ is 5 : 2
So, molar ratio in balanced reaction is 2 : 5
Hence the balanced equation is
$2\mathrm{M}\mathrm{n}{\mathrm{O}}_4^{-}+5{\mathrm{C}}_2{\mathrm{O}}_4^{2-}+16{\mathrm{H}}^{+}\to 2\mathrm{M}{\mathrm{n}}^{2+}10\mathrm{C}{\mathrm{O}}_2+8{\mathrm{H}}_2\mathrm{O}$

Hence, the correct answer is option: 'B'.