Abstract Wall mass and heat transfer rates in a square gas‐sparged, mechanically stirred reactor were measured by the electrochemical technique under the effect of various geometrical and hydrodynamic variables. For the 45° impeller, the mass transfer data fit the equation Sh = 0.7 Sc 0.33 Re 0.2 Re g 0.5 with an average deviation of ±6.9 %. For the 90° impeller, the data fit the equation Sh = 0.95 Sc 0.33 Re 0.14 Re g 0.53 with an average deviation of ±7.5 %. Gas sparging enhanced the wall mass transfer rates by factors of up to 2.61 and 3 for the 90° and 45° impellers, respectively, with a significant decrease in the total power consumption. The contribution of the present results to the operation of multiphase mechanically agitated vessels in different aspects is outlined.