Chemistry - Redox Reactions Question with Solution | TestHub

Balance in base: ${\mathrm{H}}_2\mathrm{P}{\mathrm{O}}_2^{-}$ $\to$ $\mathrm{HP}{\mathrm{O}}_3^{2-}$ + $3{\mathrm{H}}^{+}$ + $2{\mathrm{e}}^{-}$; adding $3O{\mathrm{H}}^{-}$ to both sides gives ${\mathrm{H}}_2\mathrm{P}{\mathrm{O}}_2^{-}$ + $3O{\mathrm{H}}^{-}$ $\to$ $\mathrm{HP}{\mathrm{O}}_3^{2-}$ + $2{\mathrm{H}}_2\mathrm{O}$ + $2{\mathrm{e}}^{-}$. So 3 mol $\mathrm{O}{\mathrm{H}}^{-}$ are consumed per mole of hypophosphite. Hence (a).