(a) Write any two characteristics of chemical adsorption.
(b) What is Brownian movement? What is the cause for it?
(c) What is homogeneous catalysis?

Explanation

(a) (i) High specificity: Chemisorption is highly specific and it will only occur when adsorbent and adsorbate molecules can chemically react with each other, e.g. oxygen is adsorbed on metals by oxide formation.
(ii)Surface area: Chemisorption increases with increase in surface area of the adsorbent.
Unbalanced bombardment of the particles of dispersed phase by molecules of dispersion medium cause Brownian motion. This stabilises the sol.
Brownian movement involves motion of colloidal particles in zig zag paths.
When the catalyst mixes homogeneously with the reactant(s) and form a single phase, the catalyst is said to be homogeneous and this kind of catalysis is known as homogeneous catalysis, e.g. (i) Catalytic oxidation of `SO_(2)` to `SO_(3)`, in presence of NO is an example of homogeneous catalysis.
`2SO_(2)(g) + O_(2)(g) overset("NO(g)")to 2SO_(3)(g)`