Balancing Redox Reactions - 1 | Chemical Reactions and Properties of Solutions

Bromate ion: BrO₃^-
Bromide ion: Br^-
Unbalanced reaction: BrO₃^- → Br^-

1) Balance atoms (other than O and H): Br is already balanced
2) Balance O atoms by adding H₂O molecules: BrO₃^- → Br^- + 3 H₂O
3) Balance H atoms by adding H⁺ ions: BrO₃^- + 6 H⁺ → Br^- + 3 H₂O
4) Balance charge by adding electrons: BrO₃^- + 6 H⁺ + 6 e^- → Br^- + 3 H₂O

Half-reaction under acidic conditions: BrO₃^- + 6 H⁺ + 6 e^- → Br^- + 3 H₂O

Under basic conditions: add HO^- ions to react with all H⁺ ions: HO^- + H⁺ → H₂O
BrO₃^- + 6 H⁺ + 6 e^- + 6 HO^- → Br^- + 3 H₂O + 6 HO^-
BrO₃^- + 6 H₂O + 6 e^- → Br^- + 3 H₂O + 6 HO^-
BrO₃^- + 3 H₂O + 6 e^- → Br^- + 6 HO^-

Half-reaction under basic conditions: BrO₃^- + 3 H₂O + 6 e^- → Br^- + 6 HO^-