Question

Which of the following is not characteristic of chemisorption?

• A. Adsorption is specific
• B. Heat of adsorption is of die order of $200kJmo{l}^{-1}$
• C. Adsorption may form multimolecular layers
• D. Adsorption is irreversible

Answer 1

Answer: (C)

Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface.

Various characteristics of Chemisorption are-

• High specificity: Chemisorption is highly specific and it will only occur if there is some possibility of chemical bonding between adsorbent and adsorbate.
  
• It is irreversible in nature.
• Surface area: Chemisorption increases with the increase of the surface area of the adsorbent.
• Enthalpy of adsorption: Enthalpy of chemisorption is high ($80-240$$kJ$ $mo{l}^{-1}$)) as it involves chemical bond formation.
• Chemisorption doesn't form multimolecular layers and hence option D is a correct answer.