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(physical chemistry)
A chemical adsorption process in which weak chemical bonds are formed between gas or liquid molecules and a solid surface.



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.


See references under ADSORPTION.


References in periodicals archive ?
The value of Gads obtained shows that the molecules chemisorb on the steel producing a bond resistant to penetration and competitive adsorption from the corrosive species.
This shows that Citrus reticulata peels contain alcoholic, aliphatic and aromatic acidic and phenolic, esters and ketonic constituents, which can chemisorb pollutants effectively [22-25].
2+] discharges first to form a thin layer which chemisorbs water to form adsorbed Ni[(OH).