THERMODYNAMIC PROPERTIES OF THE SYSTEM {yNaCl+(1–y)Na2HPO4}(aq) AT T = 298.15 K BY ELECTROMOTIVE FORCE MEASUREMENTS

Abstract

The mean ionic activity coefficients of NaCl in a ternary system {yNaCl+(1-y) Na_2 HPO_4 }(aq)were determined using electromotive force measurements (EMF) at T = 298.15 K. For EMF measurements, a cell of the type Na–ISE〖NaCl(m〗_NaCl), Na_2 HPO_4 〖(m〗_(KH_2 PO_4 ))AgAgCl was employed with NaCl ionic strength fractions y = (0.3012; 0.5011; 0.7706) in the range of total ionic strength of the solution I = (0.0701 – 0.9315) mol·kg-1. The Extended Pitzer model was used to analyze experimental data for the mixed electrolyte solution, and good agreement between experimental and calculated values of thermodynamic properties was found with a standard deviation of the fit of 10-3 order.