REDOX REACTION

Students,
Please remember about Redox reaction that you have learnt before. What do you think about this type of reaction? Redox comes from the words reduction and oxidation. Do you remember the reason? Please give an example of this reaction from daily life that happened around you.

Oxidation comes from the word oxigen. So, if an element reacts with oxigen, the result is an oxide, metal oxide or non metal oxide. If the metal is iron and the non metal is sulfur, please try to write down the chemical equation.

Here, I give you other examples, that is magnesium as a metal and hydrogen as a non metal.
2 Mg(s) + O2(g) --> 2 MgO(s)
2 H2(g) + O2(g) --> 2 H2O(l)

In these two reactions, Mg and H2 are oxidised by O2 and as a result, magnesium oxide and hydrogen oxide or water. So these reactions can be classified as oxidation, according to the Mg and H2. In this process, oxidation number (ON) of Mg and H change from zero to +2 and +1. Do you remember how to calculate ON?

These are a few rules to remember
1.The oxidation number of an element is zero.
2.The oxidation number of an ion is equal to the charge of the ion.
3.Hydrogen has an oxidation number of +1 (this doesn't apply to hydrides when hydrogen is -1).
4.Oxygen has an oxidation number of -2 (except in peroxides when it is -1).
It is then simply a matter of adding together all of the oxidation numbers of the elements in a compound and making sure that the total is = 0

If you look at O2, you can find that ON of O2 in both reactions change from zero to -2. Please compare the change of ON of Mg and H2 with O2. The ON of Mg and H2increase, but the ON of O2 decreases. The first reaction we call oxidation, and the second is reduction. So that reduction and oxidation occur in the same time, one transfers electrons to another. That is why these two half-reactions can not be separated.

Oxidation is the loss of electrons, reduction is the gain of electrons
Oxidation is a half equation 2 Mg --> 2 Mg2+ + 4e-.
Reduction is a half equation O2 + 4e- --> 2 O2-.

Oxidising and reducing agents
An oxidizing agent is an element which causes oxidation (and is reduced as a result) by removing electrons from another species.
A reducing agent is an element which causes reduction (and is oxidized as a result) by giving electrons to another species.
In the above example Mg is the reducing agent as it has brought about the reduction of O2 to O2-.

Students, I hope all the above explanation can help you to remember REDOX reaction and apply it to the next concept, that is balancing redox equation.