Redox (reduction-oxidation) reactions include all chemical reactions in which atoms have their oxidation state changed. This can be either a simple redox process, such as the oxidation of carbon toyield carbon dioxide (CO2) or the reduction of carbon by hydrogen to yield methane (CH4), or a complex process such as the oxidation of glucose (C6H12O6) in the human body through a series of complexelectron transfer processes.
Fundamentally, redox reactions are a family of reactions that are concerned with the transfer of electrons between species. The term comes from the two concepts ofreduction and oxidation. It can be explained in simple terms:
Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
Reduction is the gain of electrons or adecrease in oxidation state by a molecule, atom, or ion.
Although oxidation reactions are commonly associated with the formation of oxides from oxygen molecules, these are only specific examples of amore general concept of reactions involving electron transfer.
Redox reactions, or oxidation-reduction reactions, have a number of similarities to acid–base reactions. Like acid–base reactions, redoxreactions are a matched set, that is, there cannot be an oxidation reaction without a reduction reaction happening simultaneously. The oxidation alone and the reduction alone are each called ahalf-reaction, because two half-reactions always occur together to form a whole reaction. When writing half-reactions, the gained or lost electrons are typically included explicitly in order that thehalf-reaction be balanced with respect to electric charge.
Though sufficient for many purposes, these descriptions are not precisely correct. Oxidation and reduction properly refer to a change in oxidationstate — the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation state, and reduction as a decrease in oxidation state. In practice, the...
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