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Encyclopedia > Redox

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Illustration of a redox reaction

Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. Image File history File links Redox_reaction. ... Image File history File links Redox_reaction. ... Chemical reactions are also known as chemical changes. ... The oxidation number of an element in a molecule or complex is the charge that it would have if all the ligands (basically, atoms that donate electrons) were removed along with the electron pairs that were shared with the central atom[1]. It means that the oxidation number is the... In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. ...

The term redox comes from the two concepts of reduction and oxidation. It can be explained in simple terms:

Non-redox reactions, which do not involve changes in formal charge, are known as metathesis reactions. In chemistry, a formal charge (FC) on an atom in a molecule is defined as: FC = number of valence electrons of the atom - number of Lone pair electrons on this atom - half the total number of electrons participating in covalent bonds with this atom. ... Metathesis is a bimolecular process involving the exchange of bonds between the two reacting chemical species, which results in the creation of products with similar or identical bonding affiliations. ...

The two parts of a redox reaction
Rusting iron
A bonfire. Combustion consists of redox reactions involving free radicals.

## Oxidizing and reducing agents GA_googleFillSlot("encyclopedia_square");

Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. Put another way, the oxidant removes electrons from another substance, and is thus reduced itself. And because it "accepts" electrons it is also called an electron acceptor. European Union Chemical hazard symbol for oxidizing agents Dangerous goods label for oxidizing agents Oxidizing agent placard An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. ... An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. ...

Oxidants are usually chemical substances with elements in high oxidation numbers (e.g., H2O2, MnO4, CrO3, Cr2O72−, OsO4) or highly electronegative substances that can gain one or two extra electrons by oxidizing a substance (O, F, Cl, Br). R-phrases , , , , S-phrases , , , ,, , , , Flash point Non-flammable Related Compounds Related compounds Water Ozone Hydrazine Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in... The structure of the permanganate anion A permanganate is a chemical compound that contains the permanganate ion (MnO4âˆ’). Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizer. ... In chemistry, chromic acid (or Jones reagent) is a chromium (Cr) compound, yet to be isolated, that would have the formula H2CrO4. ... Osmium tetroxide is the chemical compound with the formula OsO4. ... Electronegativity is a measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... Distinguished from fluorene and fluorone. ... General Name, symbol, number chlorine, Cl, 17 Chemical series halogens Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Bromo redirects here. ...

The chemical way to look at redox processes is that the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or reducing agent loses electrons and is oxidized and the oxidant or oxidizing agent gains electrons and is reduced. The pair of an oxidising and reducing agent that are involved in a particular reaction is called a redox pair.

## Oxidation in industry

Oxidation is used in a wide variety of industries such as in the production of cleaning products.

Redox reactions are the foundation of electrochemical cells. A demonstration electrochemical cell setup resembling the Daniell cell. ...

## Examples of redox reactions

A good example is the reaction between hydrogen and fluorine: This article is about the chemistry of hydrogen. ... Distinguished from fluorene and fluorone. ...

$mathrm{H}_{2} + mathrm{F}_{2} longrightarrow 2mathrm {HF}$

We can write this overall reaction as two half-reactions: the oxidation reaction

$mathrm{H}_{2} longrightarrow 2mathrm{H}^{+} + 2e^-$

and the reduction reaction:

$mathrm{F}_{2} + 2e^- longrightarrow 2mathrm{F}^{-}$

Analysing each half-reaction in isolation can often make the overall chemical process clearer. Because there is no net change in charge during a redox reaction, the number of electrons in excess in the oxidation reaction must equal the number consumed by the reduction reaction (as shown above).

Elements, even in molecular form, always have an oxidation number of zero. In the first half reaction, hydrogen is oxidized from an oxidation number of zero to an oxidation number of +1. In the second half reaction, fluorine is reduced from an oxidation number of zero to an oxidation number of −1.

When adding the reactions together the electrons cancel:

$frac{begin{array}{rcl} mathrm{H}_{2} & longrightarrow & 2mathrm{H}^{+} + 2e^{-} mathrm{F}_{2} + 2e^{-} & longrightarrow & 2mathrm{F}^{-} end{array}}{begin{array}{rcl} mathrm{H}_{2} + mathrm{F}_{2} & longrightarrow & 2mathrm{H}^{+} + 2mathrm{F}^{-} end{array}}$

And the ions combine to form hydrogen fluoride: R-phrases , S-phrases , , , , Flash point nonflammable Related Compounds Other anions Hydrochloric acid Hydrobromic acid Hydroiodic acid Related compounds Hydrogen fluoride fluorosilicic acid Supplementary data page Structure and properties n, Îµr, etc. ...

$mathrm{H}_{2} + mathrm{F}_{2}, longrightarrow 2mathrm{H}^{+} + 2mathrm{F}^{-} longrightarrow 2mathrm{HF}$

### Other examples

• iron(II) oxidizes to iron(III):
Fe2+ → Fe3+ + e
H2O2 + 2 e → 2 OH

overall equation for the above: R-phrases , , , , S-phrases , , , ,, , , , Flash point Non-flammable Related Compounds Related compounds Water Ozone Hydrazine Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in... Hydroxide is a polyatomic ion consisting of oxygen and hydrogen: OHâˆ’ It has a charge of âˆ’1. ...

2Fe2+ + H2O2 + 2H+ → 2Fe3+ + 2H2O
2NO3 + 10e + 12 H+ → N2 + 6H2O
• iron oxidizes to iron(III) oxide and oxygen is reduced forming iron(III) oxide (commonly known as rusting, which is similar to tarnishing):
4Fe + 3O2 → 2 Fe2O3
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
The process of cell respiration also depends heavily on the reduction of NAD+ to NADH and the reverse reaction (the oxidation of NADH to NAD+). Photosynthesis is essentially the reverse of the redox reaction in cell respiration:
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

## Redox cycling

A wide variety of aromatic compounds are enzymatically reduced to form free radicals that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes and their coenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as futile cycle or redox cycling. Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... In chemistry, radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. ... Coenzyme A Coenzymes are small organic non-protein molecules that carry chemical groups between enzymes. ... Lewis electron configuration of superoxide. ...

Examples of redox cycling-inducing molecules are the herbicide paraquat and other viologens and quinones such as menadione. [1]PDF (2.76 MiB) An herbicide is used to kill unwanted plants. ... Paraquat is the trade name for N,N-Dimethyl-4,4-bipyridinium dichloride, a viologen. ... Viologen, 4,4-bipyridylium salt, compound of the form R2C10H8N22+2X- , where R can be a substituent for a nitrogen atom and the anion needed to keep charge neatrality. ... A quinone (or benzoquinone) is either one of the two isomers of cyclohexadienedione or a derivative thereof. ... Menadione is a polycyclic aromatic ketone, based on 1,4-naphthoquinone, with a 2-methyl substituent. ... â€œPDFâ€ redirects here. ... MiB redirects here. ...

## References

1. ^ Hudlický, Miloš (1996). Reductions in Organic Chemistry. Washington, D.C.: American Chemical Society, 429. ISBN 0-8412-3344-6.
2. ^ Hudlický, Miloš (1990). Oxidations in Organic Chemistry. Washington, D.C.: American Chemical Society, 456. ISBN 0-8412-1780-7.

The American Chemical Society (ACS) is a learned society (professional association) based in the United States that supports scientific inquiry in the field of chemistry. ... The American Chemical Society (ACS) is a learned society (professional association) based in the United States that supports scientific inquiry in the field of chemistry. ...

Wikibooks has a book on the topic of
General Chemistry/Redox Reactions

Image File history File links Wikibooks-logo-en. ... Wikibooks logo Wikibooks, previously called Wikimedia Free Textbook Project and Wikimedia-Textbooks, is a wiki for the creation of books. ... The Bessemer process was the first inexpensive industrial process for the mass-production of steel from a molten pig iron. ... Bioremediation can be defined as any process that uses microorganisms, fungi, green plants or their enzymes to return the environment altered by contaminants to its original condition. ... Overview of the Calvin cycle and carbon fixation The Calvin cycle (or Calvin-Benson cycle or carbon fixation) is a series of biochemical reactions that takes place in the stroma of chloroplasts in photosynthetic organisms. ... Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part... A demonstration electrochemical cell setup resembling the Daniell cell. ... English chemists John Daniell (left) and Michael Faraday (right), both credited to be founders of electrochemistry as known today. ... The Galvanic cell, named after Luigi Galvani, consists of two different metals connected by a salt bridge or a porous disk between the individual half-cells. ... Membrane potential (or transmembrane potential or transmembrane potential difference or transmembrane potential gradient), is the electrical potential difference (voltage) across a cells plasma membrane. ... Oxidative addition and reductive elimination are two important classes of reactions in organometallic chemistry. ... A reducing agent (also called a reductant or reducer) is the element or a compound in a redox (reduction-oxidation) reaction (see electrochemistry) that reduces another species. ... Thermic reactions are chemical reactions which are thermic: either highly exothermic (producing heat) or endothermic (absorbing heat). ... In chemistry, a partial oxidation reaction occurs when a substoichiometric fuel-air mixture is partially combusted in a reformer, creating a hydrogen-rich syngas which can then be put to further use, for example in a fuel cell. ...

Results from FactBites:

 Britain.tv Wikipedia - Redox (1242 words) This can be a simple redox process, such as the oxidation of carbon to yield carbon dioxide, it could be the reduction of carbon by hydrogen to yield methane (CH), or a complex process such as the oxidation of sugar in the human body, through a series of very complex electron transfer processes. Redox reactions are the foundation of electrochemical cells. The redox state is reflected in the balance of several sets of metabolites (e.g., lactate and pyruvate, beta-hydroxybutyrate and acetoacetate) whose interconversion is dependent on these ratios.
 redox: Definition and Much More from Answers.com (1752 words) Oxidation-reduction reactions, called also redox reactions, are most simply balanced in the form of chemical equations by arranging the quantities of the substances involved so that the number of electrons lost by one substance is equaled by the number gained by another substance. Industrially, many redox reactions are of great importance: combustion of fuels; electrolysis (oxidation occurs at the anode and reduction at the cathode); and metallurgical processes in which free metals are obtained from their ores. This can be a simple redox process, such as the oxidation of carbon to yield carbon dioxide, it could be the reduction of carbon by hydrogen to yield methane (CH), or it could be the oxidation of sugar in the human body, through a series of very complex electron transfer processes.
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