What are the applications of adsorption in chemical analysis?
There are various applications of adsorption in chemical analysis.
Some of which are as follows
(i) In thin layer chromatography The lower adsorbing particles comes out readily while another having higher adsorbing tendency comes out later. On this basis compounds are separated or analysed.
(ii) In adsorption indicators Surface of certain precipitate has an ability to adsorb some dyes to produce a characteristic colour e.g., AgX adsorbs eosin dye and thereby producing a characteristic colour at the end point.
(iii) In qualitative analysis Specific material has specific adsorption tendency so particular ion can be identified very easily.
(iv) In the separation of inert gases Different inert gases are adsorbed to different extents at different temperatures on coconut charcoal. This forms the basis of their separation from a mixture.
What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?
In froth floatation process sulphide ore is shaken with pine oil and water, the ore particles are adsorbed on froth that floats and the gangue particles settle down in tank. Thus, role of adsorption in froth floatation process can be understood as following processes.
(i) Adsorption of pine oil on sulphide ore particles.
(ii) Formation of emulsion takes place.
(iii) Froth is formed along with ore particles.
(iv) Mechanism of the functioning of shape selective catalysis.
As sulphide are extracted using froth floatation method therefore, only sulphide ore particles will show these type of adsorbing tendency.
What do you understand by shape selective catalysis? Why are zeolites good shape selective catalysts?
The catalytic reaction which depends upon pore structure of catalyst and the size of the reactant and product molecules is known as shape selective catalysts. Zeolites are good shape selective catalyst because of honey comb like structure.
(i) They are microporous aluminosilicates with $\mathrm{Al}-\mathrm{O} — \mathrm{Si}$ framework and general formula $M_{x / n}\left[\left(\mathrm{AlO}_2\right)_x\left(\mathrm{SiO}_2\right)_y\right] \mathrm{mH}_2 \mathrm{O}$
(ii) The reactions taking place in zeolites depend upon the size and shape of the reactant and product molecules as well as upon the pores and cavities of the zeolites.
(iii) Zeolites are widely used as catalysts in petrochemical industries for cracking of hydrocarbonds and isomerisation. They are also used for removing permanent hardness of water.
(iv) e.g., ZSM-5 is a catalyst used in petroleum industry
Alcohols $$\mathrm{\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{Dehydration}^{ZSM - 5}}}$$ Gasoline (petrol) $\qquad$ (A mixture of hydrocarbons)