High-quality ab-initio computational results for the interaction of some molecules (dihydrogen, carbon monoxide, water, ammonia, formaldehyde, nitrous oxide and methanol) with the silanol molecule H₂SiOH taken as representative of the isolated hydroxyl at the silica surface are reviewed and discussed. The self-interaction of silanol is used to mimic interacting hydroxyls at the silica surface. The interaction, have features typical of hydrogen bonding and yield a coherent set of data. Comparison with experiment indicates that silanol, though probably somewhat less acidic than the species actually present on silica, is a quite satisfactory model for such hydroxyl. The major role of electrostatics in the H-bonding formation is evidenced.