en>Bender235: /* Further reading */

2014-09-19T22:12:19Z

201.217.53.235 at 15:20, 27 June 2013

2013-06-27T15:20:50Z

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	~~I am Tabitha~~ from ~~Kelmscott studying Computing~~ and ~~Information Science~~. ~~I did my schooling~~, ~~secured 71% and hope~~ to ~~find someone~~ with ~~same interests in Mineral collecting~~.<br><br>~~my webpage~~: [~~http~~://~~www~~.~~wikihowto.in~~/~~qtoa~~/~~index~~.~~php/1239~~/~~how-~~to-~~get-free-fifa-15-coins Fifa 15 Coin Generator]~~		{{refimprove\|date=November 2013}}
			{{no footnotes\|date=November 2013}}
			'''Desorption''' is a [[phenomenon]] whereby a substance is released from or through a surface. The [[Process (science)\|process]] is the opposite of [[sorption]] (that is, either [[adsorption]] or [[Absorption (chemistry)\|absorption]]). This occurs in a system being in the state of sorption equilibrium between bulk phase (fluid, i.e. gas or liquid solution) and an adsorbing surface (solid or boundary separating two fluids). When the concentration (or pressure) of substance in the bulk phase is lowered, some of the sorbed substance changes to the bulk state.

			In chemistry, especially [[chromatography]], desorption is the ability for a chemical to move with the mobile phase. The more a chemical desorbs, the less likely it will adsorb, thus instead of sticking to the stationary phase, the chemical moves up with the solvent front.

			In chemical [[separation process]]es, [[stripping (chemistry)\|stripping]] is also referred to as desorption as one component of a liquid stream moves by [[mass transfer]] into a vapor phase through the liquid-vapor interface.

			After adsorption, the adsorbed chemical will remain on the substrate nearly indefinitely, provided the temperature remains low. However,as the temperature rises, so does the likelihood of desorption occurring. The general equation for the rate of desorption is:

			<math>R = r N^x</math>,

			where <math>r</math> is the rate constant for desorption, <math>N</math> is the concentration of the adsorbed material, and <math>x</math> is the kinetic order of desorption.

			Usually, the order of the desorption can be predicted by the number of elementary steps involved:

			Atomic or simple molecular desorption will typically be a [[Rate equation#First-order reactions\|first-order process]] (i.e. a simple molecule on the surface of the substrate desorbs into a gaseous form).

			Recombinative molecular desorption will generally be a [[Rate equation#Second-order reactions\|second-order process]] (i.e. two hydrogen atoms on the surface desorb and form a gaseous H<sub>2</sub> molecule).

			The rate constant <math>r</math> may be expressed in the form

			:<math>r=Ae^{{-E_a}/{kT}}</math>

			where <math>A</math> is the "attempt frequency" (often the Greek letter [[Nu (letter)\|<math>\nu</math>]]), the chance of the adsorbed molecule overcoming its potential barrier to desorption, <math>E_a</math> is the [[activation energy]] of desorption, <math>k</math> is the Boltzmann constant, and <math>T</math> is the temperature.

			==References==
			* {{cite book
			\|url=http://books.google.com/books?id=E7AfDCyfINYC&pg=PA375
			\|title=Introduction to Surface Chemistry and Catalysis
			\|last1=Somorjai \|first1= Gabor A.
			\|last2=Li \|first2=Yimin
			\|publisher=John Wiley and Sons
			\|year=2010
			\|at=Section 4.6
			}}

			==See also==
			* [[Adsorption]]
			* [[Sorption isotherm]]
			* [[Chemisorption]]
			* [[Gibbs isotherm]]
			* [[Moisture sorption isotherm]]
			* [[Langmuir equation]]

			[[Category:Surface chemistry]]

			{{Chemistry-stub}}

168.16.202.142 at 03:09, 20 March 2012

2012-03-20T03:09:54Z

New page

I am Tabitha from Kelmscott studying Computing and Information Science. I did my schooling, secured 71% and hope to find someone with same interests in Mineral collecting.<br><br>my webpage: [http://www.wikihowto.in/qtoa/index.php/1239/how-to-get-free-fifa-15-coins Fifa 15 Coin Generator]

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en>Bender235: /* Further reading */

201.217.53.235 at 15:20, 27 June 2013

168.16.202.142 at 03:09, 20 March 2012