JEE Main · 2023 · 25 Jan 2023 · Shift 2 · d and f Block Elements

In potassium dichromate the chromium is in the $+6$ state. When it oxidises a substrate in acidic medium it is itself reduced according to $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}+14{\mathrm{H}}^{+}+6{\mathrm{e}}^{-}\to 2C{\mathrm{r}}^{3+}+7{\mathrm{H}}_2\mathrm{O}$, each chromium gaining three electrons. The oxidation state of chromium therefore changes from $+6$ to $+3$.