Question

How do you know if it is an oxidation reduction reaction?

Answer 1

Oxidation reduction reactions are called the redox reaction. In such reactions oxidation and reduction both take place simultaneously. Loss of electrons causes oxidation and gain of electrons causes reduction. In order to identify oxidation reduction reactions we have to check the transfer of electrons.

Complete step by step answer:
Redox reactions are such types of reactions where oxidation and reduction both take place simultaneously. In redox reactions oxidation states of atoms get changed. In this reaction one species undergoes oxidation and on the other hand other species undergoes reduction. The oxidation half is identified by using the oxidation state such as increase in oxidation state or loss of electron is oxidation and the reduction half is identified where oxidation state decreases and gain of electrons takes place.
For example, $KMn{O_4}$ reacts with oxalic acid (followed by the given equation):
$2Mn{O_4}^ - + 5{C_2}O_4^{2 - } + 16{H^ + } \to 2M{n^{2 + }} + 10C{O_2} + 8{H_2}O$
By stoichiometry, $2moles$ of $KMn{O_4}$ is equivalent to $5moles$ of ${H_2}{C_2}{O_4}$ .
Here, changes in oxidation states are taking place. Increase in oxidation state is the oxidation half and the decrease in oxidation state is reduction half.

Note:
There are various redox reactions that occur because of the changes in oxidation states but without distinct electron transfer. If we talk about the combustion of wood in the presence of oxygen. We can see the oxidation state of carbon atoms in the wood increases and the oxidation state of oxygen atoms decreases and thus carbon dioxide and water are formed. The oxygen atoms undergo reduction, formally gaining electrons, while the carbon atoms undergo oxidation, losing electrons. Thus oxygen is the oxidizing agent and carbon is the reducing agent in this reaction.