Standard Potentials of Ag-AgCI Electrode and Related Thermodynamic Quantities in Dimethyl Sulfoxide-Water Mixtures from 5° to 45°C

EMF measurements were performed at 5°, 15°, 25°, 35°, and 45°C on the cell of the type Pt|H2 (g, 1 atm) |HC1 (m), DMSO (X), H2O (Y)|AgCl,Ag, where X = 5, 10, and 20 w/o (weight per cent) dimethyl sulfoxide (DMSO). The standard potentials were evaluated by means of a curve-fitting program. The mean molal activity coefficients of HC1 have been determined for molalities from 0.001 to 0.1 mol kg-1. The cell has also been used to derive (i) the primary medium effect on HC1, (ii) the relative partial molal enthalpy (L2) of HC1, and (iii) the thermodynamic constants AG0, AH, and AS’ for the transfer of HC1 from water to the respective solvent compositions (X = 5, 10, and 20). The standard emf has been expressed as a function of temperature. The electrostatic contribution of the Gibbs free energy of transfer has been calculated, based on Born's model, and the results have been interpreted in terms of acid-base interactions, as well as the structure-breaking processes of the solvents.