(a) In reference of Freundlich adsorption isotherm, write the expression for adsorption of gases on solids in the form of an equation. (b) Write an important characteristic of lyophilic solutions. (c) Based on type of particles of dispersed phase, give one example each of associated colloid and multimolecular colloid.

(a) The Freundlich adsorption isotherm is mathematically expressed as
x/m = Kp^(1/n)
It is also written as
log(x/m) = logK + (1/n)logp
or,
x/m = Kc^(1/n)
It is also written as
log(x/m) = logK + (1/n)logc
where,
x = mass of adsorbate
m = mass of adsorbent
p = Equilibrium pressure of adsorbate
c = Equilibrium concentration of adsorbate in solution
K and n are constants for a given adsorbate and adsorbent at a particular temperature.
At high pressure, 1/n = 0, hence, the extent of adsorption becomes independent of pressure.
(b) Lyophilic sols are solvent attracting. An important characteristic of these sols is that if the dispersion medium is separated from the dispersion phase by any method, the sol can be reconstituted by simply mixing the two again. That is why these sols are also known as reversible sols.
(c) Example of associated colloid: Soap solution
Example of multimolecular colloid: gold sol