Mass transfer in aqueous, turbulent flow through a sudden pipe expansion is simulated with a low reynolds number (LRN) k-e eddy viscosity model. The predicted wall-mass transfer rates are tested against experimental data, obtained with electrochemical mesurements (re= 2.1-13 x 10^4 and Sc=1460).LRN modifications to the turbulence model in the near-wall regions, coupled with the turbulent Schmidt number concept, enable successfulpredictions of wall-mass transfer rates to be obtained. For the specific case of a high Schmidt number fluid, the mass transfer boundary layer is much thinner than the hydrodynamic boundary layer. Furthermore, even low levels of turbulence in the near-wall region are shown to have significant influence on the overall wall-mass transport.