Thermodynamics of cadmium halide complex formation in acetamide-calcium nitrate tetrahydrate melt

Abstract

The complex formation between cadmium(II) ions and chloride and bromide ions in the melt of 0.8CH(3)CONH(2)-0.2Ca(NO3)(2). 4H(2)O has been studied at six temperatures between 30 and 80 degreesC. The formation constants of the complexes CdX+ and CdX2 (X=CI, Br) were determined from Emf measurements by means of Ag/AgX electrodes. The thermodynamic parameters DeltaH(mn)degrees and DeltaS(mn)degrees for the stepwise complex formation [GRAPHICS] have been estimated. The results are DeltaH(11)degrees = 4.2 kJ mol(-1). DeltaS(11)degrees = 52.4 J K-1 mol(-1), DeltaH(12)degrees = 3.3 kJ mol(-1) DeltaS(12)degrees = 40.7 J K-1 mol(-1) for the chloride complexes and DeltaH(11)degrees = -3.3 kJ mol(-1), DeltaS(11)degrees = 33.0 J K-1 mol(-1), DeltaH(12)degrees = -2.5 kJ mol(-1), DeltaS(12)degrees = 30.4 J K-1 mol(-1) for the bromide complexes. The parameters are compared with the literature data for the same process in dilute aqueous solutions and in some hydrated salt melts.