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REDOX REACTIONS 235 UNIT 7 REDOX REACTIONS Where there is oxidation, there is always reduction – Chemistry is essentially a study of redox systems. After studying this unit you will be able to Chemistry deals with varieties of matter and change identify redox reactions as a classf one kind of matter into the other. Transformation of of reactions in which oxidation matter from one kind into another occurs through the various types of reactions. One important category of such and reduction reactions occur simultaneously; reactions is Redox Reactions. A number of phenomena, define the terms oxidation, both physical as well as biological, are concerned with reduction, oxidant (oxidising redox reactions. These reactions find extensive use in agent) and reductant (reducing agent); pharmaceutical, biological, industrial, metallurgical and agricultural areas. The importance of these reactions is explain mechanism of redox apparent from the fact that burning of different types of reactions by electron transfer fuels for obtaining energy for domestic, transport and process; other commercial purposes, electrochemical processes use the concept of oxidation for extraction of highly reactive metals and non-metals, number to identify oxidant and manufacturing of chemical compounds like caustic reductant in a reaction; soda, operation of dry and wet batteries and corrosion of classify redox reaction into combination (synthesis), metals fall within the purview of redox processes. Of late, environmental issues like Hydrogen Economy (use of decomposition, displacement liquid hydrogen as fuel) and development of ‘Ozone Hole’ and disproportionation reactions; have started figuring under redox phenomenon. suggest a comparative order among various reductants and 7.1 CLASSICAL IDEA OF REDOX REACTIONS – oxidants; OXIDATION AND REDUCTION REACTIONS balance chemical equations Originally, the term oxidation was used to describe the using (i) oxidation number addition of oxygen to an element or a compound. Because (ii) half reaction method; of the presence of dioxygen in the atmosphere (~20%), many elements combine with it and this is the principal learn the concept of redox reactions in terms of electrode reason why they commonly occur on the earth in the processes. form of their oxides. The following reactions represent oxidation processes according to the limited definition of oxidation: 2 Mg (s) + O 2 (g) → 2 MgO (s) (7.1) S (s) + O (g) → SO (g) (7.2) 2 2 Reprint 2026-27