Give the mechanism of heterogeneous catalysed reaction.

Explanation

Mechanism of catalysis involves following steps:
i) Diffusion of reactant molecules towards the surface of catalyst. ii) Adsorption of the reactant molecules on the surface of the catalyst by forming loose bonds with the catalyst due to the presence of free valences. iii) Occurence of a chemical reaction between the reactants and the catalyst forming an intermediate. iv) Desorption of product molecule from the surface due to the lack of its affinity for the catalyst surface. So makes the surface free for fresh adsorption of reactant molecules. v) Diffusion of product molecules away from the surface of catalyst.