Thermodynamics of Cadmium Chloride in 2-Butanone + Water Mixtures (5, 10, and 15 Mass%) from Electromotive Force Measurements

The emf (electromotive force) of the cell: CdHgx (two phase) | CdCl2 (m) | AgCl | Ag in 2-butanone + water mixtures (containing 5, 10, and 15 mass% 2-butanone) was measured at varying temperature (293.15, 298.15, 303.15, 308.15, and 313.15 K) and in the CdCl2 molality range from 0.002 to 0.02 mol-kg−1. At each temperature the standard emf of the cell (Emo) was determined using potentiometric data and literature values for the stability constants of chlorocadmium complexes. The Emo values were used to calculate the standard thermodynamic quantities for the cell reaction, the stoichiometric mean molal activity coefficients of CdCl2, and the thermodynamic functions for CdCl2 transfer from water to 2-butanone + water mixtures. The transfer process is a forced one and results in an entropy decrease. The transfer functions were compared to those obtained for the same electrolyte in acetone + water mixtures, as well as to those for HBr in ketone + water mixtures. Medium effects upon CdCl2 were calculated and discussed for the examined mixtures (2-butanone + water).