What is catalysis ? How is catalysis classified ? Give two examples for each type of catalysis.

Explanation

Catalysts : A substance which alters the rate of a chemical reaction without itself being consumed in the process, is called a catalyst.
The action of catalyst in altering the rate of a chemical reaction is called catalysis.
Types of catalysts : Catalysis is classified into two types as
a) Homogeneous catalysis and b) Heterogeneous catalysis.
Homogeneous catalysis : The catalytic process in which the catalyst is present in the same phase as that of reactants, is known as homogeneous catalysts.
Ex : a) `2 SO_(2(g)) + O_(2(g)) overset(NO_((g)))to 2SO_(3(g))` [Lead chamber process]
b) `CH_(3)CHO_((g)) overset(I_(2(g)))to CH_(4(g)) +CO_((g))`
Heterogeneous catalysts : The catalytic process in which the catalyst is present in a phase different from that of the reactants is known as heterogeneous catalysis.
Ex: a) `2SO_(2(g)) +O_(2(g)) underset(V_(2)O_(5(S)))overset(Pt_(s))to 2SO_(3(g))`
b) `N_(2(g)) + 3H_(2(g)) overset(Fe_((s)))to 2NH_(3(g))` [Haber's process].