Question

What part of a reaction involves oxidation or reduction, but not both?

Answer 1

Half equations, which we use to solve redox reactions.

Explanation:

Consider the reduction of intensely purple `MnO_4^-` to give colourless `Mn^(2+)`:

`MnO_4^(-) + 8H^+ +5e^(-)rarr Mn^(2+) +4H_2O`

As written, this is a reduction reaction, the which includes electrons, which are conceived to reduce the manganese centre. The reduction reaction must be accompanied by a corresponding oxidation reaction to supply the electrons.

I acknowledge that the use of electrons is a little bit abstract; but their use indicates electron transfer, which characterizes redox behaviour and allows us to balance such equations.