Balance equation for given reaction is,
6 Fe²⁺ + Cr₂O₇²⁻ + 14 H⁺ → 6 Fe³⁺ + 2 Cr³⁺ + 7 H₂O
Oxidation Reaction:
6 Fe²⁺ → 6 Fe³⁺ + 6 e⁻
Iron has lost 2 electron per mole and 6 electrons per 6 moles. As Fe oxidation state of Fe has changed from +2 to +3 so it has lost one electron and is oxidized.
Reduction Reaction:
Cr₂O₇²⁻ + 6 e⁻ → 2 Cr³⁺
Chromium has gained 3 electrons per mole and 6 electrons per 2 moles. As oxidation state of Cr has changed from +6 to +3 so it has gained 3 electrons and is reduced.
