# How can I recognize oxidation reduction reactions?

Sep 4, 2014

The easiest way is to look for elements whose oxidation state (charge) changes during a reaction.

Here is an example of a redox reaction:

3Mg(s) + $2 {\text{FeCl}}_{3}$(aq) → $3 {\text{MgCl}}_{2}$(aq) + 2Fe(s)

Mg has no charge before the reaction· After, it has a charge of +2 — meaning it was oxidized.

Iron goes from a +3 charge before the reaction to a an oxidation state of 0 after the reaction — meaning it was reduced (reduced charge due to addition of electrons).

If no elements in a reaction change oxidation state (for example: double replacement reaction) the reaction is not a redox reaction.

Hope this helps.

Noel P.