Modern adsorption theory does not explain the action of

According to modern adsorption theory of catalysis, there are free valencies on the surface of solid catalysts and the mechanism involves the following steps-

1. Diffusion of reactant molecules towards the surface of the catalyst.
2. Adsorption of the reactant molecules on the surface of the catalyst by forming loose bonds with catalyst due to free valencies.
3. Occurrence of chemical reaction between reactants and the catalyst forming an intermediate.
4. Desorption of the product molecule from the surface due to lack of its affinity for the catalyst surface.
5. Diffusion of product molecules away from the surface of the catalyst.