Chemisorption

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chemisorption

[′kem·i‚sȯrp·shən]
(physical chemistry)
A chemical adsorption process in which weak chemical bonds are formed between gas or liquid molecules and a solid surface.

Chemisorption

 

the adsorption of substances from the surrounding medium by a liquid or solid, accompanied by the formation of chemical compounds. In a narrower sense, chemisorption is regarded as the chemical binding of a substance by the surface of a solid, or chemical adsorption.

Considerable heat is released in chemisorption: the heat of chemisorption is usually 84–126 kilojoules per mole (kJ/mole), or 20–30 kcal/mole; in some cases—for example, the chemisorption of oxygen on metals—it may exceed 420 kJ/mole (100 kcal/mole). Like chemical reactions, chemisorption usually requires considerable activation energy. Thus, chemisorption is accelerated when the temperature is increased (activated adsorption). Chemisorption is selective—that is, it depends on the chemical affinity of the adsorbed substance for the solid surface.

Physical methods, such as spectroscopy, electron paramagnetic resonance, nuclear magnetic resonance, electron and ion field-emission microscopy, and slow-electron diffraction, are used to study chemisorption. The process plays an important role in heterogeneous catalysis, gas purification, and vacuum technology.

REFERENCES

See references under ADSORPTION.

M. U. KISLIUK

References in periodicals archive ?
The X-Ray diffraction patterns of original, activated and chemisorbed ash samples from the 1st and 4th ESP are presented in Figures 1 and 2, respectively.
1] for carboxyl (COOH) stretch vibration, (42), (43) indicate that most dodecanoic acid molecules have been chemisorbed on the surface and form salts with the metal or metal oxide.
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The Lopinski group demonstrated that chlorination of n-type H/Si(111) surfaces leads to a significant increase in the surface conductivity that can be attributed to the formation of a minority carrier channel resulting from the electron withdrawing nature of the chemisorbed chlorine.
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It is reported that some HALS compounds are chemisorbed on the pigment surface under losing its free radical scavenging ability.
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