NCERT Class XII Chemistry
Chapter - Surface Chemistry
Questions with Solutions
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Question : 2
Total: 35
What is the difference between physisorption and chemisorption?
Solution:
| Physisorption | Chemisorption |
| The adsorbate and adsorbentare held by weak van der Waalsforces. | The adsorbate and adsorbent areheld by forces similar to a chemicalbond. |
| Heat of adsorption is of theorder of 20 kJ/mol. | Heat of adsorption is of the order of200 kJ/mol. |
| It is reversible. | It is irreversible. |
| It decreases with increase intemperature and occurs at lowertemperatures. | It increases with temperature andoccurs at high temperature. |
| It is not specific in nature, i.e., allgases are adsorbed on all solidsto some extent. | It is specific in nature and occursonly when a chemical bond isformed between the adsorbate andadsorbent. |
| Multimolecular layers may beformed on the adsorbent. | Usually unimolecular layer is formedon the adsorbent. |
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