Reduction

You can use three definitions to describe reduction:

✓ The gain of electrons

✓ The loss of oxygen

✓ The gain of hydrogen

Gain of electrons

Chemists often see reduction as the gain of electrons. In the process of electroplating silver onto a teapot, for example, the silver cation is reduced to silver metal by the gain of an electron. The following equation shows the silver cation’s gaining the electron:

Ag⁺ + e^– → Ag

When it gains the electron, chemists say that the silver cation has been reduced to silver metal.

Loss of oxygen

In some reactions, seeing reduction as the loss of oxygen in going from reactant to product is easy. For example, a reaction with carbon monoxide in a blast furnace reduces iron ore (primarily rust, Fe2O3) is to iron metal:

Fe₂O_3(s) + 3CO_(g) → 2Fe_(s) + 3CO_2(g)

The iron has lost oxygen, so chemists say that the iron ion has been reduced to iron metal.

Gain of hydrogen

In certain cases, you can describe a reduction as the gain of hydrogen atoms in going from reactant to product. For example, carbon monoxide and hydrogen gas can be reduced to methyl alcohol:

CO_(g) + 2 H_2(g) → CH₃OH_(l)

In this reduction process, the CO has gained the hydrogen atoms.