Question

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

Answer 1

The process in which the rate of the chemical reaction is altered by the use of different catalysts is known as catalysis. The chemical species which alter the rate of the reaction but are not consumed in the reaction are known as catalysts. The catalysts can be recovered from the chemical reaction. A small amount of catalyst is sufficient to carry out the reaction.

Complete step by step answer:
The two groups into which the phenomenon of catalysis can be divided are as follows:
a) Homogeneous catalysis:
The catalysis in which the phase of the catalyst and the reactant are the same is known as homogeneous catalysis.
In homogeneous catalysis, the catalyst and the reactant have the same physical state i.e. both the catalyst and the reactant can be in solid, liquid or gaseous phase.
Example of homogeneous catalysis is reaction of sulphur dioxide gas with oxygen gas in presence of nitric oxide. The reaction leads to the production of sulphur trioxide gas.
The chemical equation when sulphur dioxide gas with oxygen gas in presence of nitric oxide is as follows:
${\text{2S}}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ + }}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ }}\xrightarrow{{{\text{NO}}\left( {\text{g}} \right)}}{\text{ 2S}}{{\text{O}}_{\text{3}}}\left( {\text{g}} \right)$
In the reaction, the catalyst, reactants and products all are in the same physical state .i.e. gaseous state.
b) Heterogeneous catalysis:
The catalysis in which the phase of the catalyst and the reactant are not the same is known as heterogeneous catalysis.
In heterogeneous catalysis, the catalyst and the reactant do not have the same physical state. The catalyst is in solid powdered form. Heterogeneous catalysis is also known as surface catalysis.
Example of heterogeneous catalysis is reaction of sulphur dioxide gas with oxygen gas in presence of solid platinum metal. The reaction leads to the production of sulphur trioxide gas.
The chemical equation when sulphur dioxide gas with oxygen gas in presence of solid platinum metal is as follows:
${\text{2S}}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ + }}{{\text{O}}_{\text{2}}}\left( {\text{g}} \right){\text{ }}\xrightarrow{{{\text{Pt}}\left( {\text{s}} \right)}}{\text{ 2S}}{{\text{O}}_{\text{3}}}\left( {\text{g}} \right)$
In the reaction, the catalyst is in solid state and the reactants and products are in gaseous state.

Note: Do not confuse between catalyst and catalysis. Catalyst is the chemical species which alter the rate of the reaction but are not consumed in the reaction. The process in which the rate of the chemical reaction is altered by the use of different catalysts is catalysis.