What is the equivalent weight of ${\text{H}}_2{\text{C}}_2{\text{O}}_4$ in the reaction with ${\text{KMnO}}_4$?

Solution

1. The reaction is $5{\text{H}}_2{\text{C}}_2{\text{O}}_4+2{\text{MnO}}_4^{-}+6{\text{H}}^{+}\to 10{\text{CO}}_2+2{\text{Mn}}^{2+}+8{\text{H}}_2\text{O}$.
2. In ${\text{H}}_2{\text{C}}_2{\text{O}}_4$, carbon is in the $+3$ oxidation state.
3. In ${\text{CO}}_2$, carbon is in the $+4$ oxidation state.
4. The change per carbon atom is $1$, and there are $2$ carbons per molecule, so n-factor is $2$.
5. Equivalent weight is $\text{Molar Mass}/2$.
6. Hence the answer is (B).