Surface Chemistry

Which of the following statement is incorrect regarding physissorptions?

  1. It occurs because of van der Waal's forces.
  2. More easily liquiefiable gases are adsorbed readily.
  3. Enthalpy of adsorption (ΔHadsorption) is low and positive.
  4. Under high pressure it results into multi molecular layer on adsorbent surface.

Answer

Enthalpy of adsorption in physisorption is negative:

ΔG = ΔH - TΔS

As the entropy decreases (ΔS = -ve) the ΔH must be negative having a high magnitude. Therefore, the spontaneous adsorption will have negative enthalpy change.

The correct option is C.