Absorption : It is a phenomena in which a substance is uniformly distributed all over the surface.
Adsorption : the existence of a substance at a surface in different concentration than in the adjoining bulk is called adsorption. It is a selective adsorption.
Types of adsorption: Depending upon the nature of forces between the molecules of adsorbate and the adsorbent, the adsorption may be classified as:
1. Physisorption
2. Chemisorption
Freundlich adsorption isotherm: the adsorption of a gas on the surface of solid depends upon the pressure of gas. The extent of adsorption is generally expressed as x/m, where m is the mass of adsorbent and x is the mass of adsorbate when equilibrium has been attained. On the basis of experimental studies, Freundlich established the following relationship between the amount of gas adsorbed (x) per unit mass of adsorbate (m) and the pressure (p).
x/m =kp1/n
Where n is a constant
(whole number)which depends upon the nature of adsorbate and adsorbent.
(whole number)which depends upon the nature of adsorbate and adsorbent.
Factor affecting the adsoption of gases on solids :
1. Nature of gas : the easily liquefiable gases like NH3, HCL, CO2, etc. are adsorbed to the great extent then the permanent gases such as H2, O2, N2< etc.
2. Nature of adsorbent : activated charcoal is the most common adsorbent for the gases. The gases such as H2, O2, N2, are adsorbed on the metal Ni, Pd, etc.
3.
