We investigate the adsorption of trichlorosilane (HSiCl3) on silica using infrared spectroscopy and examine the subsequent reactions of the chemisorbed species with water. Ab initio frequency calculations of model compounds that closely resemble the structure of possible surface species are used to aid in the assignment of infrared bands. The frequency of the Si-H stretching and bending modes of the chemisorbed HSiCl3 is sensitive to the structure and is used in combination with the information obtained from the low frequency bands of the Si-Cl and Si-s-O-Si modes (Si-s refers to a surface Si atom) to obtain a clearer picture of the species formed on the silica surface.