Question

a. Write any two differences between lyophilic and lyophobic colloids.
b. What is heterogeneous catalysis? Give an example.
c. Give an expression for Freundlich adsorption isotherm.

Answer 1

a.

S. No.	Lyophilic colloids	Lyophobic colloids
$1$	Disperse phase has high affinity for dispersion medium	Disperse phase has low affinity for dispersion medium.
$2$	They are easily formed by direct mixing or on heating.	They cannot be prepared directly. They can be prepared by special methods.
$3$	They are reversible in nature.	They are irreversible in nature.
$4$	They are quite stable and are not easily coagulated.	They are unstable and are easily coagulated by adding a small amount of suitable electrolyte.

b. Hetergeneous catalysis is a process where reactants and catalyst are in different phases. For example, in the following reaction, reactants $2S{O}_{2_{\left(g\right)}}$ and $O_{2_{\left(g\right)}}$ are in gaseous state whereas platinum catalyst is in solid state.
$2S{O}_{2_{\left(g\right)}}+O_{2_{\left(g\right)}}\stackrel{P{t}_{\left(s\right)}}{\to }2S{O}_{3_{\left(g\right)}}$

c. Expression for Freundlich adsorption isotherm is $\frac{x}{m}=K{P}^{\frac{1}{n}}$ or $lo{g}_{10}\frac{x}{m}=\frac{1}{n}lo{g}_{10}P+lo{g}_{10}K$