Mean Activity Coefficients of NaBr in NaBr + Na₂SO₄+ H₂O Ternary System at 298.15 K Determined by Potential Difference Measurements

Abstract

The mean activity coefficients of NaBr in the NaBr + Na 2 SO 4 + H 2 O ternary system were determined at the total ionic strength ranging from (0.0500 to 3.0000) mol·kg –1 at 298.15 K by potential difference measurements from the galvanic cell without liquid junction: Na–ISE|NaBr( m 1 ), Na 2 SO 4 ( m 2 )|Br–ISE. The mean activity coefficients of NaBr were compared with those different ionic strength fractions y B of Na 2 SO 4 with y B = (0.8, 0.6, 0.4, 0.2, and 0). The experimental results showed that Na–ISE and Br–ISE in this work had a good Nernst response, and the mean activity coefficients of NaBr in NaBr + Na 2 SO 4 + H 2 O mixtures were calculated using the Nernst equation. Mixing interaction parameters of θ Br – ·SO 4 2– and φ Na + ·Br – ·SO 4 2– in Pitzer’s equation, which had not been previously reported, were evaluated from the present measurements of the mean activity coefficients of NaBr. In addition, the osmotic coefficients, water activity, and the excess Gibbs energy of this system were calculated by the Pitzer’s equations.