Which element is reduced in the reaction below? fe2+ + h+ + cr2o72- → fe3+ + cr3+ + h2o?

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.