| Nature of Forces | Weak Van der Waal’s forces are present. | Strong chemical forces are present. |
| Heat of Adsorption | The heats of adsorption are low viz. about 20-40 kJ mol−1. | The heats of adsorption are high viz. about 40-400 kJ mol−1. |
| Effect of Temperature | Usually occur at low temperature and decreases with the increase in temperature. | Occur at high temperature and may or may not decreases with the increase in temperature. |
| Effect of Pressure | The rate of increase in adsorption with pressure is much higher at high pressure. | The rate of increase in adsorption usually decreases as the pressure increases. |
| Reversibility | Reversible in nature. | Irreversible in nature. |
| Specificity | It is not specific in nature i.e. all gases are adsorbed on all solids to some extent. | It is specific in nature and occurs only when there is some possibility of compound formation between the gas being adsorbed and the solid adsorbent. |
| Activation Energy | Involves very small activation energy. | Generally involves high activation energy. |
| Formation of Surface Compounds | No surface compound is formed. | Surface compounds are formed. |
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