The second dissociation constant of sulfuric acid at various temperatures by the conductometric method

The thermodynamic second dissociation constant K₂ for sulfuric acid has been determined by conductivity measurements of aqueous sulfuric acid solutions at various temperatures. The data are treated by using two different methods developed with two independent assumptions due to Noyes et al. and Shedlovsky. Both methods require the knowledge of relevant ionic conductivities, which may be calculated from the Onsager limiting law. The values for K₂ obtained with these two methods show excellent agreement. The value of 0.0103 mol-L^–1 at 25°C agrees with the best literature value of 0.0102 mol-L^–1 within the experimental uncertainty, as also does the enthalpy of dissociation which is derived from the derivative of the temperature coefficient of K₂.