Name the two groups into which phenomenon of catalysis can be divided. Give an example of each group with the chemical equation involved.

The phenomenon of catalysis can be divided into two groups.

Homogeneous catalyst: In the homogeneous catalyst is present in the same phase as the reactant, it is called a homogeneous catalyst and this type of catalyst is called is called homogeneous catalysis.

For example: 2SO_2(g) + O_2(g)   2SO_3(g)

Heterogeneous catalyst: In the heterogeneous catalyst present in a different phase as a reactant, it is called a heterogeneous and this type of catalyst is called heterogeneous catalysis.

For example: N_2(g) + 3H_2(g) 2NH_3(g)