Monday, September 22, 2014

Difference Between Physical Adsorption and Chemical Adsorption

S.No.
PHYSICAL ADSORPTION
CHEMICAL ADSORPTION
1. Molecules are held due to vanderwaal’s forces. Molecules are held due to chemical bond forces.
2. Heat of adsorption are in the range of 20 – 40KJ/Mol. Heat of adsorption are in the range of 40 – 400 KJ/Mol.
3. Activation energy are small. Activation energy are appreciable.
4. Usually occurs rapidly at low temperatures and decreases with increase in temperature. Can occur at high temperature.
5. Usually completely reversible. Often irreversible.
6. The extent of adsorption is approximately related to the ease of liquification of gas. No such correlation is there.
7. Not very specific. Often highly specific.
8. Form multilayer on the surface of adsorbent. Forms unimolecular layer.
9. No surface compound is formed Surface compounds are formed.

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