Transition-state theory is often used to calculate the rate constant of a chemical reaction. Usually, it gives quite good results for gas-phase reactions but not for reactions in solution since the interactions of the solvent molecules with the reactants are not included in the theory. Kramers formulated an extension of the transition-state theory that included these interactions. They are represented by a friction coefficient that often is related to the viscosity of the solvent by Stoke's law. For reactions on the surface of a crystalline catalyst, there will also be an effect on the rate constant from the interaction between the reactants and the oscillating substrate atoms. In contrast to reactions in solution, where the friction coefficient is related to the viscosity of the solvent, there exists no simple property of the solid that may be directly related to a friction coefficient for the motion of the adsorbed molecule on the surface. In this paper, we propose a method that may be used to calculate a friction coefficient that may be used in Kramers theory to calculate the rate constant for a chemical reaction on the surface of a crystalline solid.