Surface Chemistry

                                               SURFACE CHEMISTRY

• Adsorption :

(i) The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed as adsorption.
(ii) It is a surface phenomenon.
(iii) The concentration of adsorbate increases only at the surface of the adsorbent.

• Adsorbate : It is the substance which is being adsorbed on the surface of another substance.

• Adsorbent : It is the substance present in bulk, on the surface of which adsorption is taking place.

• Desorption : It is the process of removing an adsorbed substance from a surface on which it is adsorbed.

• Absorption :

(i) It is the phenomenon in which a substance is uniformly distributed throughout the bulk of the solid.

(ii) It is a bulk phenomenon.

(iii) The concentration is uniform throughout the bulk of solid.

• Sorption : When adsorption and absorption take place simultaneously, it is called sorption.

• Enthalpy or heat of adsorption : Since, adsorption occurs with release in energy, i.e., it is exothermic in nature. The enthalpy change for the adsorption of one mole of an adsorbate on the surface of adsorbent is called enthalpy or heat of adsorption.