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 byhydrogen to yield methane (CH4), or a complex process such as the oxidation ofglucose (C6H12O6) in the human body through a series ofcomplex electron transferprocesses.
Redox reactions, or oxidation-reduction reactions, have a number of similarities to acid-base reactions. Fundamentally, redox reactions are a family of reactions thatare concerned with the transfer of electrons between species.
The term comes from the two concepts of reduction and oxidation. It can be explained in simple terms:
* Oxidation isthe loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
* Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
Like acid-base reactions,redox reactions 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 calleda half-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 thatthe half-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 changein oxidation state — 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, thetransfer of electrons will always cause a change in oxidation state, but there are many reactions that are classed as "redox" even though no electron transfer occurs (such as those...
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