Mean Ionic Activity Coefficients of NaBr in the Ternary System NaBr–SrBr₂–H₂O at 288.15 K using the Cell Potential Method

Abstract

In this paper, a sodium ion selective electrode (Na-ISE) and a bromide ion selective electrode (Br-ISE) were used to form a liquid-free potential reversible battery: Na-ISE|NaBr (m 1 ) and SrBr 2 (m 2 )|Br-ISE. The mean ionic activity coefficients of NaBr in the ternary system NaBr− SrBr 2 −H 2 O at 288.15 K were determined using the cell potential method. In this system, the total ionic strength, I, ranges from 0.0100 up to 2.0000 mol • kg −1 for different ionic strength fractions y b of SrBr 2 , that is, y b = (0.0, 0.2, 0.4, 0.6, and 0.8). The results show that Na-ISE and Br-ISE have a great Nernst effect. The mean ionic activity coefficients of NaBr in NaBr− SrBr 2 −H 2 O were calculated using the Nernst equation, and the cell potential values were measured. The Pitzer ion interaction parameters θ Na + • Sr 2+ and ψ Na + • Sr 2+ • Br − were fitted using the Pitzer model, and experimental results in this work, and the mean ionic activity coefficients of SrBr 2 at 288.15 K were also calculated according to the Pitzer model. Finally, the osmotic coefficient Φ, water activity a w , and excess Gibbs energy G E of the ternary system were also calculated.