Electrochemical and thermodynamic studies of the ion-pair formation of chloropentamminecobalt(III) ion in ethyl alcohol-water media containing different dicarboxylate ligands |
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Authors: | Zaghloul A A El-Naggar G A Abuo Ali S B |
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Affiliation: | Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt. |
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Abstract: | The ion-pair dissociation constants, K(D), of the ion-pair formed between chloropentamminecobalt(III) ion (CpX(2+)) and a variety of dicarboxylate ligands, have been determined from EMF measurements of a cell composed of glass and calomel electrodes. Measurements were made in water and in aqueous binary mixtures of ethyl alcohol, over a wide range of solvent composition (0-60 wt% ethyl alcohol), at six different temperatures (ranging from 30 to 55 degrees C at intervals of 5 degrees C). The thermodynamic parameters of association DeltaG(ass)(0), DeltaH(ass)(0) and DeltaS(ass)(0) have been calculated and discussed. DeltaH(ass)(0)-DeltaS(ass)(0), DeltaS(ass)(0)-DeltaS(1(or 2))(0), DeltaG(ass)(0)-G(1(or 2))(0) and DeltaH(ass)(0)-DeltaH(1(or 2))(0) correlations among different solvent media and different dicarboxylate ligands were examined (where 1 and 2 denote the first and the second dissociation reactions of the studied dicarboxylic acids). The pK(D) value has been correlated with the dielectric constant of the medium according to Born's equation. |
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