1.

What is physisorption? State its characteristics.

Answer»

When the adsorbent such as gas molecules are accumulated at the surface of a solid on account of weak van der Waals forces, the adsorption is termed as physical adsorption or physisorption.

Characteristics:

  • The van der Waals forces involved in physical adsorption are similar to forces causing condensation of gas into liquid. Thus, heat is released in physisorption.
  • The heat released during physisorption is of the same order of magnitude as heat of condensation.
  • Due to weak nature of van der Waals forces, physisorption is weak in nature.
  • The adsorbed gas forms several layers of molecules at high pressures.
  • The extent of adsorption is large at low temperatures.
  • The equilibrium is attained rapidly.
  • Physisorption is readily reversed by lowering of pressure of gas or by raising temperature.


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