The standard enthalpy of physical adsorption typically falls within the low range of . This magnitud — Surface Chemistry Chemistry Question
Question
The standard enthalpy of physical adsorption typically falls within the low range of $20\text{ to }40\text{ kJ mol}^{-1}$. This magnitude of heat release is physically most comparable to the heat of which of the following standard phase transitions?
💡 Solution & Explanation
Physical adsorption relies on intermolecular van der Waals forces, which are the exact same types of forces responsible for the condensation of gases into liquids. Therefore, physical adsorption only occurs significantly near the liquefaction temperature of the gas, and its enthalpy ($20-40\text{ kJ/mol}$) is on the same order of magnitude as the heat of liquefaction (vaporization).