Abstract:

The thermodynamic properties of the system HCl-NaCl-C3H8O3-H2O was studied by means of emf measurement in the following cells without liquid junctions:
Pt, H2(1.013×105Pa)|HCl(m), C3H8O3(x), H2O(1-x)|AgCl-Ag             (A)
Pt, H2(1.013×105Pa)|HCl(mA), NaCl(mB), C3H8O3(x), H2O(1-x)|AgCl-Ag  (B)
at constant total ionic strength I=0.5, 1.0. 1.5 and 2.0mol.kg-1 , from 5 to 45 ℃, where mA and mB are the molalities of HCl and NaCl. respectively, x is the weight fraction of glycerol in the mixed solvent, which was 0.1 during all measurements.
The standard electrode Potential of Ag-AgCl in the mixed solvent have been determined from cell (A). The activity coefficients of HCl, γA in the mixed solvent system have been determined from cell (B). The results show that the activity coefficients of HCl in HCl-NaCl solution still obeys Harned rule, and lgγA is a linear function of the reciprocal of the absolute temperature at constant composition of the mixture. Relative molar enthalpies of HCl LA arc linear function of the ionic strength fraction of NaCl at constant total ionic strength temperature. The standard Gibbs free energies of transfer of HCl have been calculated. The primary secondary and total medium effect of HCl have been calculated and discussed.

Key words: Standard electrode potential, Activity coeffiecient, Relative molar enthalpies