Comparison between physisorption and chemisorptions
|
Physisorption (Vander Waal's adsorption) |
Chemisorption (Langmuir adsorption) |
|
Low heat of adsorption usually in range of 20-40 kJ/mol |
High heat of adsorption in the range of 50-400 kJ/mol |
|
Force of attraction are Vander Waal's forces. |
Forces of attraction arechemical bond forces. |
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It is reversible |
It is irreversible |
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It is usually takes place at low temperature and decreases with increasing temperature. |
It takes place at high temperature. |
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It is related to the case of liquefication of the gas. |
It is not related. |
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It forms multimolecular layers. |
It forms monomolecular layers. |
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It does not require any activation energy. |
It requires high activation energy. |
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High pressure is favourable. Decrease of pressure causesdesorption |
High pressure is favourable. Decrease of pressure does not cause desorption. |
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It is not very specific. |
It is highly specific. |