Thermodynamic properties of hydrochloric acid in dimethylformamide-water mixtures at different temperatures

The standard potential of the Ag-AgCl electrode has been determined from the e.m.f. of a cell of the type Pt,H₂(gas 1 atm)|HCl (m), Me ₂N·CHO (X), H₂O (100 - X)|AgCl, Ag at five different temperatures in the range 5-45°C. Measurements were made in dimethylformamide-water mixtures [X = 5 and 10% (w/w)] for acid concentrations in the range 0.005-0.2 mol kg^-1. The mean activity coefficients of HCl have been calculated. The standard thermodynamic quantities (ΔG°, ΔH°, ΔS°, and °C_p°) accompanying the transfer of HCl from water to the respective solvent media have been computed from the variations of ΔE_N°(the difference in standard e.m.f. between the ordinary water and the mixed solvent on the mole-fraction scale) with temperature. The results have been discussed with respect to the solvent structure and acid-base behaviour on the transfer process.