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• The oxidation-reduction reaction is also known as a redox reaction. In this reaction, one reactant is oxidized and other is reduced. In balancing an oxidation-reduction reaction, they must be first divided into two half reactions: one is oxidation reaction and other is reduction reaction.
• The balancing of redox reaction is complicated as compared to simple balancing. It is necessary to determine the half reactions of reactants undergoing oxidation and reduction. On adding the two halfreactions, net total equation can be obtained. This method of balancing redox reaction is known as half equation method.

Because number of electrons lost during oxidation is equal to the number of electrons gained during reduction.In an oxidation-reduction reaction, one of the species oxidizes and the other reduces. Here, oxidation means loss of electrons and reduction means gain of electrons.The half- reaction method is used to balance the oxidation reduction reaction. In this method, first the unbalanced chemical reaction splits into two half reactions in which one is oxidation and other is reduction. The solutions in which the electrochemical reactions take place can be acidic, basic or neutral. The number of electrons lost by species undergoing reduction must be equal to the number of electrons gained by the species undergoing oxidation thus, the charge must be balanced.

The charge should be balanced in oxidation-reduction reactions because the number of electrons lost during oxidation is equal to the number of electrons gained during reduction.