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How to Balance Redox Reactions - Balancing Redox Reactions

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

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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

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