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A half reaction is either the oxidation or reduction reaction component of a redox reaction. A half reaction is obtained by considering the change in oxidation states of individual substances involved in the redox reaction.

Consider the reaction below:

Cl2 + 2Fe2+ → 2Cl + 2Fe3+

The two elements involved, iron and chlorine, each change oxidation state; iron from 2+ to 3+, chlorine from 0 to 1−. There are then effectively two half-reactions occurring. These changes can be represented in formulas by inserting appropriate electrons into each half-reaction:

Fe2+ → Fe3+ + e
Cl2 + 2e → 2Cl

In the same way given two half-reactions it is possible, with knowledge of appropriate electrode potentials, to arrive at the full (original) reaction.

See also

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Half-reaction". A list of authors is available in Wikipedia.
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