The subensemble kinetics of a platinum sulfur covalent chemical reaction at the solution/surface interface of a model industrial catalyst support was examined using single-molecule fluorescence microscopy (SMFM) and was found to exhibit biexponential first-order kinetic behavior. The observed kinetics was a convolution of the observation probability and chemical reaction rate. These results suggest that deconvolution strategies may be broadly important for obtaining accurate chemical reaction kinetics with SMFM.