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Speech on Teachers Day by Student for Teachers in English

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Speech on Teachers Day by Student for Teachers in English

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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.

195k x/ m x/ m 244k

P equilibrium

1

x/m=kp1/n

Log X/m

slope=1/n

L o g K Log P 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. 10....