Dichromate ion oxidizes iron(II) in acid to give iron(III) and chromium(III). Which balanced equation is correct?

1. The iron half-reaction is Fe2+ giving Fe3+ plus one electron. 2. For chromium, balance Cr first: Cr2O7 2- gives 2Cr3+. 3. Balance the 7 oxygen atoms with 7 water molecules on the right. 4. Those waters need 14 hydrogen atoms, so add 14 H+ on the left. 5. Charge on the left is now 12+ and on the right 6+, so add 6 electrons on the left. 6. Multiply the iron half-reaction by 6 so that 6 electrons appear in each half. 7. Adding and cancelling the 6 electrons gives 6Fe2+ + Cr2O7 2- + 14H+ giving 6Fe3+ + 2Cr3+ + 7H2O. 8. Options with 3 or 2 iron ions do not supply the 6 electrons the chromium half needs. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_