IGCSE Coordinated Science: Redox

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7.2 Redox

1 Define oxidation and reduction in terms of oxygen loss/gain, and identify such reactions from given information.


(a) The gain or addition of oxygen by an atom, molecule or ion.



(b) The loss or removal of electrons from an atom, ion or molecule.



(c). An oxidizing agent is the species that gives the oxygen or removes the electrons.



(a) The removal of oxygen in a compound.



(the “O” is lost. )


(b) The gain or addition of electrons to an atom, molecule or ion




(c) A reducing agent is the species that removes the oxygen and “donates” the electrons.

An easy way to memorize the electron part of oxidization and reduction is : OILRIG

Oxidation ILoss, Reduction Is Gain. (In terms of electrons)

2 Define redox in terms of electron transfer,and identify such reactions from given information.

Redox reaction is a reaction with involves both oxidation and reduction. In a nutshell, OIL RIG happens simultaneously.



1. Copper (II) Oxide + Hydrogen –> Copper + Water


Let’s see what’s going on here and why this is a redox reaction.

CuO becomes Cu. Is oxygen gained or lost? Lost of course! And we learned, lost of oxygen is reduction which is precisely what’s going on here. CuO is reduced to Cu

Now, let’s look at H2. H2 becomes H2O. Oxygen is gained here, so H2 is oxidized into H2O.

As we can see here, both oxidation (from the H2) and reduction (from the CuO) is taking place. That’s why  a redox reaction is occurring

Ok, try the one below by yourself. Try to figure out:

    • Which substance is oxidized?
    • Which substance is reduced?
      • Is this reaction an example of a redox reaction?

2.iron(III) oxide + carbon monoxide –> iron + carbon dioxide


  •  The iron(III) oxide is reduced to iron, the carbon monoxide is oxidised to carbon dioxide
    • Since both oxidation and reduction occur here, this is an example of a redox reaction.

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4 Responses to IGCSE Coordinated Science: Redox

  1. zonga says:

    Chemistry is my worst subject :/

  2. Nikhil says:

    There is a mistake in the definition of OILRIG.
    At the moment, it says (Oxidation Is Loss Reduction Is Loss)
    It should be (Oxidation Is Loss Reduction Is Gain)

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