THE THERMODYNAMIC BEHAVIOR OF HYDROGEN BROMIDE IN AQUEOUS-SOLUTIONS OF BARIUM BROMIDE

The thermodynamic behavior of hydrogen bromide in aqueous mixtures of barium bromide as reflected in activity coefficients was studied at temperatures ranging from 278.15 K to 318.15 K at 10 K intervals and at constant ionic strengths ranging from 0.10 mol·kg-1to 3.0 mol·kg-1. Electromotive-force measurements were made on the cell without liquid junction:. Pt|H2(g, p = 101.325 kPa)|HBr(mA), BaBr2(mB)|AgBr(s)|Ag(s). Activity coefficients of HBr were calculated from the observed e.m.f.s using the Nernst expression. The activity coefficients of HBr were analyzed using the treatment of Harned and also the comprehensive ion-interaction model of Pitzer. Activity coefficients for HBr in the salt mixture follow Harned’ rule at ionic at ionic strengths up to 2.0 mol·kg-1. The Pitzer mixing parameters SΘH.Baand ΨH.Ba.Br(including higher-order electrostatic effects) and ΘH.Baand ΨH.Ba.Br(excluding higher-order effects) and their temperature derivatives have been determined and are compared with the results for similar systems. The activity coefficients and excess enthalpies for HBr and BaBr2have also been calculated using Pitzer’ formalism at the experimental temperatures and compared with the results of systems previously studied. © 1993 Academic Press Ltd.