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

Explanation

As the gaseous molecules of the reactants are adsorbed on the surface of solid catalyst, their concentration on the surface increases and they lie close to each other. Greater the concentration, faster is the reaction. Closeness of reactant molecules to each other also given them a better chancel to react. Moreover, adsorption is an exothermic process. The heat released further increases the rate of reaction.