Temperature and Concentration Dependences of the Electrical Conductance, Diffusion and Kinetic Parameters of Selenium Dioxide Solutions in Ordinary and Heavy Water

摘要

On the basis of conductivity studies, empirical equations describing the temperature and concentration dependences of the electrical conductance of SeO2 solutions in ordinary and heavy water were derived. Values of the equivalent conductivity of ions at infinite dilution, the first dissociation constant of selenous acid in the temperature region 12 to 45°C and the thermodynamic parameters of the dissociation process were determined. Using these values, the absolute mobility, the transport numbers of the ions and their diffusion coefficients were calculated. Furthermore, the values of the transition energies Δ E tr. o for the ions were calculated at different temperatures. The dependencies observed were interpreted using Samoylov’s theory for positiveegative hydration of the ions. It was shown that the HSeO3 ? and DSeO3 ? ions were positively hydrated and stabilized the solvent structure, but these effects diminished with an increase of the temperature. The temperature dependences of the hydration numbers and the effective ionic radii were determined. The values of the changes of the Gibbs energy, entropy and enthalpy for the transitions of ions from one quasi-equilibrium state to another were calculated at different temperatures.