Studies on Mean Activity Coefficients of NaBr in NaBr–SrBr 2 –H 2 O Ternary System at 298.15 K by EMF Method

The mean activity coefficients for NaBr in the (NaBr + SrBr 2 + H 2 O) ternary system were determined by electromotive force (EMF) measurements of the following cell without liquid junction: Na + –ISE–NaBr ( m A ), SrBr 2 ( m B )–Br – –ISE At the total ionic strengths ranging from 0.01 mol·kg –1 up to 2.00 mol·kg –1 at 298.15 K for different ionic strength fractions y B of SrBr 2 with y B = (0.0, 0.2, 0.4, 0.6, and 0.8). The activity coefficient results were interpreted based on the Harned rule and Pitzer model. Furthermore, the Pitzer ion interaction parameters θ Na + Sr 2+ and φ Na + Br – Sr 2+ were calculated. those parameters obtained with the Pitzer model were used to calculate the values of the mean activity coefficients of SrBr 2, the osmotic coefficients, solvent activity, and the excess Gibbs free energy for the whole series of the mixed electrolyte system that was studied.