Redox Reactions

Redox reactions are the chapter that quietly runs through the rest of chemistry. Rusting, respiration, burning fuel, extracting a metal from its ore, a battery driving a torch — all of them are electron transfer, and this chapter gives you the language for it. You start with the oldest definition, oxidation as adding oxygen, and watch it grow into the electronic definition and then into the oxidation number, a bookkeeping tool that works even when no electron is fully transferred. From there the chapter becomes practical: sorting reactions into four types, balancing equations by two different methods, doing the arithmetic behind a permanganate titration, and finally reading a table of electrode potentials to predict whether a reaction will happen at all. It is a short chapter with a high return. Oxidation numbers and balancing appear in almost every JEE and NEET paper, sometimes on their own and often hidden inside an inorganic or electrochemistry question, and the equivalent concept you meet here is the foundation for the whole of Class 12 electrochemistry.