Balancing redox equations: ion-electron and oxidation-number methods
Redox Reactions · Chemistry
Study notes
Balance in acid: MnO₄⁻ + Fe²⁺ → Mn²⁺ + Fe³⁺. Step 1: Halves: MnO₄⁻ → Mn²⁺ (reduction); Fe²⁺ → Fe³⁺ (oxidation). Step 2: Mn: add 4 H₂O right, 8 H⁺ left: MnO₄⁻ + 8H⁺ → Mn²⁺ + 4H₂O. Step 3: Charge: left +7, right +2 → add 5 e⁻ left. Step 4: Fe half × 5 (5 e⁻): MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 4H₂O + 5Fe³⁺. Atoms ✓, charge +17 = +17 ✓.