How to Balance Redox Reactions - Balancing Redox Reactions

By Anne Marie Helmenstine, Ph.D., About.com Guide

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Balancing Redox Reactions - Balance the Atoms

To balance the atoms of each half-reaction, first balance all of the atoms except H and O. For an acidic solution, next add H₂O to balance the O atoms and H⁺ to balance the H atoms. In a basic solution, we would use OH^- and H₂O to balance the O and H.

Balance the iodine atoms:

2 I^- → I₂

The Mn in the permanganate reaction is already balanced, so let's balance the oxygen:

MnO₄^- → Mn²⁺ + 4 H₂O

Add H⁺ to balance the 4 waters molecules:

MnO₄^- + 8 H⁺ → Mn²⁺ + 4 H₂O

The two half-reactions are now balanced for atoms:

MnO₄^- + 8 H⁺ → Mn²⁺ + 4 H₂O