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

Abstract

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), Me₂N·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 ΔC_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.