Which of the following statements is incorrect regarding physissorptions ?
- (A)It occurs because of vander Waal's forces.
- (B)More easily liquefiable gases are adsorbed readily.
- (C)Under high pressure it results into multi molecular layer on adsorbent surface.
- (D)Enthalpy of adsorption is low and positive.✓ Correct
Answer: (D)
Solution
Adsorption is always an exothermic process, so the enthalpy of physisorption is low in magnitude but negative in sign, not positive. Describing it as low and positive is therefore the incorrect statement. The rest are sound: physisorption rests on weak van der Waals forces, gases that liquefy easily are held more readily, and at high pressure the adsorbate can build up into multilayers on the surface.
JEE Main · 2009 · 12 Apr 2009 · Offline · Single correct option