Question

Physical adsorption of a gaseous species may change to chemical adsorption with:

• A. decrease in temperature
• B. increase in temperature
• C. increase in surface area of adsorbent
• D. decrease in surface area of adsorbent

Answer 1

The correct option is B increase in temperature

Physical adsorption of a gaseous species may change to chemical adsorption with increase in temperature.

As temperature increases, the energy possessed by reactant molecules increases. At a certain temperature, this energy becomes greater than or equal to the activation energy, This results in the formation of a chemical bond.

For example:
Dihydrogen is first adsorbed on nickel by van der Waals’ force (Physisorption). By increasing the temperature, molecules of hydrogen then dissociate to form hydrogen atoms which are held on the surface​ of nickel (Chemisorption).