How does a solid catalyst enhance the rate of combination of gaseous molecules?

Explanation

When gaseous molecules come in contact with the surface of a solid catalyst, the gaseous molecules are held with the surface of the catalyst by weak forces on the surface. This increases the concentration of reactants on the surface. Different molecules adsorbed side by side have better chance to react and form new molecules. This increases the rate of reaction. Moreover, adsorption is an exothermic process. The heat released in the process of adsorption is utilised in increasing the reaction rate.