Answer: 20-40 kJ/mol.
- A 80-240 kJ/mol
- B 400-600 kJ/mol
- C above 1000 kJ/mol
- D 20-40 kJ/mol
Correct answer: D. 20-40 kJ/mol
Explanation: Physisorption involves weak van der Waals forces, so its enthalpy is small, about 20-40 kJ/mol, unlike chemisorption.
A typical adsorption isotherm: x/m (mass adsorbed per gram of adsorbent) rises steeply at low pressure, then flattens into a saturation plateau as the adsorbent surface fills up.
Concept context
Explore the chemistry that happens at interfaces, from catalysts that speed up industrial reactions to colloids like milk, smoke, and gels that surround us every day.