Chemistry - Redox Reactions Question with Solution | TestHub

Oxidation: $2C{\mathrm{r}}^{3+}$ + $7{\mathrm{H}}_2\mathrm{O}$ $\to$ $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}$ + $14{\mathrm{H}}^{+}$ + $6{\mathrm{e}}^{-}$. Reduction: ${\mathrm{S}}_2{\mathrm{O}}_8^{2-}$ + $2{\mathrm{e}}^{-}$ $\to$ $2S{\mathrm{O}}_4^{2-}$ (× 3). Overall: $2C{\mathrm{r}}^{3+}$ + $3{\mathrm{S}}_2{\mathrm{O}}_8^{2-}$ + $7{\mathrm{H}}_2\mathrm{O}$ $\to$ $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}$ + $6S{\mathrm{O}}_4^{2-}$ + $14{\mathrm{H}}^{+}$. ${\mathrm{H}}^{+}$ produced per $\mathrm{C}{\mathrm{r}}^{3+}$ = 14/2 = 7. Hence (d).