In the present lecture on surface chemistry, we began by distinguishing between physisorption and chemisorption and also between monolayer adsorption and multiplayer adsorption. The binding energies in physisorption are much smaller and in the range of 8 to 25 kJ/mole. A relation between the amount of adsorbate adsorbed on a given surface at constant temperature and the equilibrium concentration of the substrate in contact with the adsorbent is known as Adsorption Isotherm. We have outlined the main ingredients of some important isotherms such as the adsorption isotherms of Gibbs, Freundlich and Langmuir

A multiplayer adsorption was characterized through the BET isotherm.

The heat of a reaction was obtained using an adsorption isotherm. We also outlined the mechanisms of unimolecular and bimolecular reactions at surfaces. The Langmuir – Hinshelwood mechanism and the Langmuir – Rideal mechanism of bimolecular surface reactions were described in detail. Towards the end, the role of adsorption in surface catalysis was highlighted and the other applications of adsorption were listed.