This work focuses on the investigation of multiscale mass transfer processes at freely rising single spherical bubbles with superimposed chemical reaction. For this purpose, the oxygen mass transfer without chemical reaction, calculated from numerical simulations and experimental investigations is compared quantitatively. Moreover the impact of the sulfite-sulfate reaction on the concentration field is shown qualitatively. It becomes obvious that numerical simulations provide more detailed information of the velocity field, while experiments represent a valid analysis of the concentration field. Thus bidirectional validation and combined usage of the more significant results lead to an improved calculation of the local oxygen mass flow.