Home » Ask & Discuss » Chemistry. » Inorganic Chemistry « Back to Discussion

Inorganic Chemistry

New kid on the Block

Joined:	17 Mar 2010
Post:	8

17 Mar 2010 09:30:53 IST

0 People liked this

685

Why adsorption is exothermic

None

Why adsorption is exothermic

Share this article on:

Comments (4)

prashanth debbadwar

New kid on the Block

Joined: 17 Mar 2010

Posts: 8

17 Mar 2010 09:52:56 IST

Like 1 people liked this

Bond forming is always exothermic process,bond breaking is endothermic process.Adsorption is analogus to bond formation so adsorption is always exothermic

Dasvidaniya

Blazing goIITian

Joined: 9 May 2009

Posts: 831

17 Mar 2010 10:12:41 IST

Like 3 people liked this

see this link

http://www.goiit.com/posts/list/physical-chemistry-why-is-adsorption-always-exothermic-989593.htm

Adsorption is always exothermic. we can be explained in two ways.

i) Adsorption leads to a decrease in the residual forces on the surface of the adsorbent. This causes a decrease in the surface energy of the adsorbent. Therefore, adsorption is always exothermic.

(ii) ΔH of adsorption is always negative. When a gas is adsorbed on a solid surface, its movement is restricted leading to a decrease in the entropy of the gas i.e., ΔS is negative. Now for a process to be spontaneous, ΔG should be negative.

ΔG = ΔH − TΔS

Since ΔS is negative, ΔH has to be negative to make ΔG negative. Hence, adsorption is always exothermic.

edison

Forum Expert

Joined: 19 Oct 2006

Posts: 7452

22 Jun 2011 18:02:49 IST

Like 0 people liked this

During adsorption bonds are formed which releases energy, as a result of which it is exothermic.

Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface.

This process creates a film of the adsorbate (the molecules or atoms being accumulated) on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid. The term sorption encompasses both processes, while desorption is the reverse of adsorption. It is a surface phenomenon.

Similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent, or metallic) of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates.

The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding). It may also occur due to electrostatic attraction.

Adsorption is present in many natural physical, biological, and chemical systems, and is widely used in industrial applications such as activated charcoal, capturing and using waste heat to provide cold water for air conditioning and other process requirements (adsorption chillers), synthetic resins, increase storage capacity of carbide-derived carbons for tunable nanoporous carbon, and water purification. Adsorption, ion exchange, and chromatography are sorption processes in which certain adsorbates are selectively transferred from the fluid phase to the surface of insoluble, rigid particles suspended in a vessel or packed in a column.

spiderman

Blazing goIITian

Joined: 29 Oct 2008

Posts: 535

25 Jun 2011 01:33:32 IST

Like 0 people liked this

Simple logic,stable things have less energy.If adsorption is taking place it means that system is moving towards stability,so to have less energy system ejects energy in the form of heat energy...hence getting an exothermic reaction

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team