ADSORPTION - The accumulation of molecular species at the surface rather than in the bulk of a solid or liquid is termed adsorption

DESORPTION - The process of removing an adsorbed substance from a surface on which it isadsorbed is called desorption

SORPTION - The process in which both adsorption and absorption take place

ADSORBATE - The molecular species or substance, which concentrates or accumulates at the surface is termed adsorbate

ADSORBENT - the material on the surface of which the adsorption takes place is called adsorbent.

DG = -ve DH = -ve DS = -ve

Production of high vacuum, Gas masks , Control of humidity, Removal of colouring matter from solutions, Heterogeneous catalysis , Separation of inert gases, In curing diseases , Froth floatation process , Adsorption indicators ,Chromatographic analysis

Nature of adsorbate

Nature of adsorbent

Surface area of adsorbent

Activation of adsorbent

Temperature

Pressure

PHYSISORPTION - If accumulation of gas on the surface of a solid occurs on account of weak van der Waals’ forces, the adsorption is termed as physical adsorption or physisorption

CHEMISORPTION - When the gas molecules or atoms are held to the solid surface by chemical bonds, the adsorption is termed chemical adsorption or chemisorption

CATALYSIS - The prcess in which catalyst has been used

CATALYST - Substances, which accelerate the rate of a chemical reaction and themselves remain chemically and quantitatively unchanged after the reaction, are known as catalysts. Berzelius suggested the term catalyst

PROMOTERS - Promoters are substances that enhance the activity of a catalyst

POISON - poisons decrease the activity of a catalyst

Modern adsorption Theory 1. Diffusion of reactants to the surface of the catalyst 2. Adsorption of reactant molecules on the surface of the catalyst 3. Occurrence of chemical reaction on the catalyst’s surface through formation of an intermediate 4. Desorption of reaction products from the catalyst surface 5. Diffusion of reaction products away from the catalyst’s surface

Emzymes - also known as biocatalyst, Protein molecules with highly specific structure

Mechanism of enzyme catalysis - Generally known as lock & key mechanism

Characteristics of Enzymes 1. Most highly efficient 2. Highly specific nature 3. Highly active under optimum temperature (298-310K) 4. Highly active under optimum pH (pH values 5-7) 5. Increasing activity in presence of activators and co-enzymes 6. Influence of inhibitors and poisons

Activity - Ability of a catalyst to increase the rate of a reaction

Selectivity - The selectivity of a catalyst is its ability to direct a reaction to yield a particular product

Shape selective catalyst - The catalytic reaction that depends upon the pore structure of thecatalyst and the size of the reactant and product molecules is called shape-selective catalysis.

On the basis of physical state

On the basis of interaction between DP & DM

On the basis of type of colloidal particles

Chemical methods - oxidation , reduction , double decomposition & Hydrolysis

Electrical disintegration or Bredig’s Arc method

Peptization

colligative properties

Optical properties

Brownian movement

Colour

Electrical Properties

Charge

Coagulation or precipitation

Dialysis

Electrodialysis

Ultrafiltration

Liquid-liquid colloidal system Two types of emulsions. (i) Oil dispersed in water (O/W type) and (ii) Water dispersed in oil (W/O type).

Blue colour of the sky , Fog, mist and rain , Food articles , Blood , Soils , Formation of delta

Electrical precipitation of smoke (Cottrell precipitator) , Purification of drinking water , Medicines , Tanning (Hardening of leather) , Cleansing action of soaps and detergents , Photographic plates and films , Rubber & industrial products