Differential surface stress measurements performed using the estance technique and simultaneous measurements of the differential capacitance provide experimental evidence for deviation of n-tin oxide electrode's properties from the electrocapillary relationship that has the form of the classical Lippmann equation. The differential stress curves consist of two distinct regions. At positive potentials, where the electrical properties of n-tin oxide electrode are consistent with the Mott-Schottky model, the differential stress does not depend upon polarization and is insensitive to solution pH. Tn this region, the main contribution to the surface stress originates from the ordered dipole layer, which could include water molecules. In the negative potential range, where deviations from the Mott-Schottky model occur, the differential stress curves exhibit nonmonotonic behavior and become pH sensitive. The similar behavior of differential surface stress and semiconductor electrode charge was observed in this potential range.