An acidified solution containing dichromate(VI) ions is reacted with iron(II) ions according to the following balanced ionic equation:
Cr2O72−(aq)+14H+(aq)+6Fe2+(aq)⟶2Cr3+(aq)+6Fe3+(aq)+7H2O(l) \text{Cr}_2\text{O}_7^{2-}(\text{aq}) + 14\text{H}^+(\text{aq}) + 6\text{Fe}^{2+}(\text{aq}) \longrightarrow 2\text{Cr}^{3+}(\text{aq}) + 6\text{Fe}^{3+}(\text{aq}) + 7\text{H}_2\text{O}(\text{l}) Cr2O72−(aq)+14H+(aq)+6Fe2+(aq)⟶2Cr3+(aq)+6Fe3+(aq)+7H2O(l)Which species acts as the reducing agent in this reaction?
Fe2+(aq)\text{Fe}^{2+}(\text{aq})Fe2+(aq)
Cr2O72−(aq)\text{Cr}_2\text{O}_7^{2-}(\text{aq})Cr2O72−(aq)
Cr3+(aq)\text{Cr}^{3+}(\text{aq})Cr3+(aq)
Fe3+(aq)\text{Fe}^{3+}(\text{aq})Fe3+(aq)