In adsorption-desorption phenomena, interaction among adatoms can cause multiple steady states and, consequently, hysteresis loops. Starting from a master equation and applying a mean field approximation to obtain the kinetic equations, adsorption on a heterogeneous surface with two types of randomly distributed adsorbent sites is characterized by different activation energies. Moreover, interaction among adsorbates contributes to the total activation energy. In general, depending on the values of the kinetic parameters and the heterogeneity degree, up to three stable steady states can exist for values of the parameter J, which measures the interaction energy, greater than the critical one, Jc. Once the other parameters have been fixed and considering different heterogeneity degrees, the highest Je is obtained for the case of a 50-50% site distribution. Mobility of adatoms on the surface disfavors multistability, and interactions stronger than those corresponding to a case without mobility are required to cause multiplicity of stable steady states. On the other hand, a dimerization reaction catalyzed by a surface like the one above described does not change essentially the number of stable steady states. Thus, for the case considered, multiplicity is a result due to the adsorption process and dogs not depend on the reaction one. Multistability causes different reaction rates for given conditions, depending on the initital states. When three or four types of adsorbent sites are considered, multistability does not appear. Also, when different continuous distributions of types of adsorbent sites are considered, multistability is also destroyed. Therefore, it; can be concluded that an "excess" of surface heterogeneity prevents the occurrence of multistability in adsorption with interacting adsorbates.