Second ionization constant of sulfuric acid in H2O and D2O from 150 to 300 °C at p = 11.5 MPa using flow AC conductivity

Abstract

A custom-built flow-through AC conductivity instrument was used to measure the deuterium isotope effect on the ionization quotient of bisulfate from 150 to 300 °C, at p = 11.5 MPa. Standardized solutions of KCl, HCl, KOH, KHSO4, K2SO4, and H2SO4 were prepared in light and heavy waters and their conductivities were measured and fitted with the Quint-Viallard conductivity model to obtain single ion conductivities at infinite dilution for K+, Cl−, H+, OH−, HSO4−, and SO42−. These are the first conductivities of DSO4− and SO42− measured in heavy water at any temperature, and the first ionization constants for bisulfate reported in heavy water above 225 °C. The deuterium isotope effect on the chemical equilibrium constant, ΔpK2a = pK2a,D − pK2a,H, was found to increase with temperature, in contrast to the behaviour seen for other simple oxyacids.