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Questions
Give two important characteristics of physisorption.
What are the important characteristics of physical adsorption?
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Solution
- It is reversible; adsorbed gas can be easily removed by lowering pressure or increasing temperature.
- Heat of adsorption (enthalpy) is low, about 20-40 kJ/mol.
- The forces involved are weak van der Waals’ forces of attraction.
- It increases with an increase in pressure.
- It forms multilayers of adsorbate on the adsorbent surface.
- It is non-specific; almost any gas can be physically adsorbed.
- Adsorption decreases with an increase in temperature.
- Gases with higher critical temperatures (easily liquefiable) are adsorbed more readily.
- The process has almost zero activation energy and occurs rapidly.
Notes
Students should refer to the answer according to their questions.
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