What is the purpose of half-reactions in balancing redox equations?

Half-reactions are essential in balancing oxidation-reduction (redox) equations because they allow complex processes to be analyzed in terms of electron transfer. Since any redox reaction can be broken down into a complementary pair of hypothetical half-reactions—one representing oxidation and the other reduction—they provide a systematic way to ensure the overall chemical equation is balanced.1

The purpose of using half-reactions includes:

• Balancing Electrons: When combining half-reactions, the electrons produced in one must cancel out the electrons consumed in the other to result in a valid overall chemical reaction.1
• Predicting Spontaneity: By breaking a reaction into two half-reactions with known redox potentials, one can calculate the net potential of the reaction. If the resulting value is positive, the reaction is expected to occur spontaneously.23
• Isolating Processes: They emphasize that reduction or oxidation are characteristic reactions of a specific chemical system, independent of the specific agent used to bring about the change.1