CBSE Class 12 Chemistry Surface Chemistry Notes Set B

Chapter-5 SURFACE CHEMISTRY

The branch of the Chemistry wich deals with the study of surface

phenomena is called surface Chemistry.

POINTS TO BE REMEMBERED: ---

1. Adsorption: - The accumulation of molecules species at the surface rather in the bulk of a solid or liquid is termed adsorption.

2. Desorption:-Removal of adsorbate from the surface of adsorbent is known as Desorption.

3. Sorption:-When adsorption and absorption both takes place simultaneously.

4. Type of adsorption: - On the basis of interaction between adsorption and absorption, adsorbate are of two types:

(i)Physical adsorption/physisorption: - When weak vander waal interaction involve between adsorbate and adsorbent.

(ii) Chemical adsorption/chemisortion:-When chemical bonds form between adsorbate and adsorbent.

5. Adsorption isotherm:-The variation in the amount of gas adsorbed by the adsorbent with pressure at constant temperature can be expressed by means of

a curve termed as adsorption isotherm.

6. Application of adsorption:-

(a) Removal of colouring matter from solution using animal charcoal.

(b)Chromatographic analysis is based on adsorption.

7. Freundlich adsorption isotherm:-It is a graph which shows relationship between the quality of gas adsorbed by unit mass of solid adsorbent and pressure at a particular temperature.

8 .Factors affecting adsorption:-

(i)Surface area: - Adsorption increases with increases of surface area of adsorbent.

(ii)Nature of adsorbate:- Easily liquefiable gases are readily adsorbed.

(iii)Temperature:-Low temperature is favorable for physical adsorption and High temperature for chemisortion.

(iv)Pressure: - Pressure increases, adsorption increases.

9. CATALYSIS:- Substances which alter the rate of chemical reaction and themselves remain chemically and quantitatively unchanged after the reaction are known as catalyst and the phenomenon is known as catalysis.

13. Adsorption theory of Heterogeneous catalysis – It explains the mechanism of heterogeneous catalyst. The mechanism involves 5 steps:-

a. Diffusion of reactants to the surface of catalyst.

b. Adsorption of reactant molecules on the surface of catalyst.

c. Chemical reaction on the catalyst surface through formation of an intermediate.

d. Desorption of reaction product from the catalyst surface.

e. Diffusion of reaction product away from the catalyst surface.

 

Please click the link below to download CBSE Class 12 Chemistry-Surface Chemistry.