Reduction

Definition

Reduction can be defined in different terms: as a gain of electrons or hydrogen or the loss of oxygen by an atom or a molecule.

Overview

Reduction in Terms of Electron Transfer

Reduction is the gain of electrons.

For example, in the reaction between iron and copper sulfate solution,

$$ \mathrm{F}\mathrm{e}+{\mathrm{CuSO}}_4\to \mathrm{C}\mathrm{u}+{\mathrm{FeSO}}_4 $$

Copper sulfate and iron sulfate are both ionic compounds. If rewritten as an ionic equation, it turns out that sulfate ions are spectator ions, and the equation can be written as:

$$ \mathrm{F}\mathrm{e}+{\mathrm{Cu}}^{2+}\to \mathrm{C}\mathrm{u}+{\mathrm{Fe}}^{2+} $$

It can be seen that copper is reduced from copper (II) ions to metal copper (Cu^o) by gaining two electrons

$$ {\mathrm{Cu}}^{2+}+2{\mathrm{e}}^{-}\to \mathrm{C}\mathrm{u} $$

Reduction in Terms of Hydrogen Transfer

Reduction is the gain of hydrogen.

• Hydrogen atoms are transferred from hydrazine (N₂H₄) to oxygen in the following reaction:

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