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: CdHg_x (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 (E_m^o) was determined using potentiometric data and literature values for the stability constants of chlorocadmium complexes. The E_m^o 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).