Exam Style Question - 3

Question: Combine the half-equations below to give the overall equation for the reaction of acidified manganate(VII) ions with iron(II) ions.
MnO₄^- + 8H⁺ + 5e^- → Mn²⁺ + 4H₂O
Fe²⁺ → Fe³⁺ + e^-Step 1: the number of electrons lost must equal the number gained. The manganate(VII) half-equation gains 5 electrons, so the iron half-equation is multiplied by 5: 5Fe²⁺ → 5Fe³⁺ + 5e^-Step 2: add the two half-equations together and cancel the electrons, which now appear equally on both sides.Overall redox equation: MnO₄^- + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂OCheck the charges: left side = -1 + 8 + 10 = +17; right side = +2 + 15 = +17. The equation is balanced. The mole ratio of MnO₄^- to Fe²⁺ is 1:5.