Chemistry – Oxidation & Reduction explained!
This article has been written by Stephane Biggs, a VCE Physics, VCE Further Maths, VCE Math Methods & VCE Specialist Maths Tutor at Learnmate. If you’re interested in private tutoring from Stephane then please check out her page here.
If you’re like me, you’ll find this chapter terribly confusing in the textbook… But a little explanation can go a long way. It’s actually quite easy to balance redox equations when you know the steps and understand all the terms involved. There are a lot of juicy points that can be scored, so this article will focus on explaining in a simple way what all the terms mean and how to use them in tongue-twisting exercises! First up: oxidation.
Oxidation is the process of oxidizing. It occurs when the charge of the reactant goes up. For example lead oxidizes in the following unbalanced reaction:
Pb —> Pb2+
The charge of the lead (Pb) has gone from 0 to 2+. The charge has increased. In English, we would say that oxidation has occurred. The Pb has been oxidized to Pb2+. Since the charge is going up, oxidation occurs when the reactant loses electrons. Confusing? Don’t think of oxidation in terms of electrons, think of it in terms of charge.
Reduction, on the other hand, is the process of reducing. It occurs when the charge of the reactant is reduced (going down). For example H+ ions can be reduced to H2 with the following unbalanced reaction:
2H+ —> H2
The charge of the H+ has gone from +1 to 0 The charge has decreased. We therefore say that reduction has occurred. The H+ has been reduced to H2. Since the charge is being reduced, reduction occurs when the reactant gains electrons.
In summary, when imagining oxidation and reduction in your head – what it means – you need to think in terms of charge. Reduction occurs, when the charge goes down, or is reduced. You mustn’t think in terms of the electrons, because reduction occurs when there is a gain of electrons, which can be quite confusing… so focus on the charge only when picturing oxidation and reduction in your mind.
Oxidants & Reductants
Only once you’ve fully digested what oxidation and reduction mean, should you move onto this subheading. At first sight, it may seem very confusing: when a reactant is oxidized, that reactant is a reductant; on the other hand, when a reactant is reduced, it is an oxidant!
To help explain this seeming contradiction, you need to picture an oxidant as an oxidizing agent. The oxidant will cause the other reactants to be oxidized, even though the oxidant itself is being reduced. The same principle applies in reverse for reductants: they are reducing agents – they cause the other reactants to be reduced.
The best way to make oxidation, reduction, oxidants and reductants part of your vocabulary without having to think deeply about them for 30 seconds every time, is to practice, practice, practice. Very soon, it will all click and make sense. Do plenty of exercises – twice if necessary. Once you fully grasp the meaning of these terms without thinking twice, you will be in a much better position to solve more complex chemistry questions, such as balancing redox equations. If you have any questions, feel free to get in touch.
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