Question

a) Give any three difference between physisorption and chemisorption.
b) i) Mention the role of alum in the purification of drinking water.
ii) Give an example for oil dispersed in water emulsion.

Answer 1

a) Three difference between physisorption and chemisorption.

Physisorption	Chemisorption
It involves physical or van der waals forces between the particles of adsorbate and adsorbent	It involves chemical bonds (covalent bonds) between adsorbate and adsorbent particles.
It has low heat of adsorption (20-40 kJ/mol)	It has high heat of adsorption (40-200 kJ/mol)
It is relatively weak.	It is relatively strong.

b) i) Alum attracts other fine particles and suspended material in raw water, and settles down at the bottom of the container. Thus, it purifies drinking water.
ii) Milk is an example for oil dispersed in water emulsion. Liquid fat particles are dispersed in water.