The adsorption of a number of Brønsted acids of differing strengths has been studied on stoichiometric and defective Sn0₂ (110) surfaces. The extent of dissociation of these acids depends on the surface composition and the strength of the acid. Two crystallographically inequivalent types of oxygen vacancies can be introduced onto SnO0₂ (110) surfaces, and the kinetics of the reactions of Brønsted acids is influenced by the number and type of oxygen vacancies present on each surface. The site requirement for dissociation of Brønsted acids has been described as a coordinatively unsaturated cation and an available anion. On the Sn00₂ ( 110) surfaces studied, this site requirement was seen to be a necessary but not sufficient condition for dissociation. In contradiction to the generally accepted idea that the presence of defects increases reactivity, the most defective SnO₂ (110) surface considered showed the lowest activity for dissociation for all adsorbates studied. / Ph. D.