CONDUCTOMETRIC INVESTIGATION OF MAGNESIUM (II), CALCIUM (II) AND BARIUM (II) COMPLEXES IN AQUEOUS SOLUTION

MOHAMED, ABD ALLAH A.; AL–ARIQUI, WADIE S.; BAKR, MOUSTAFA F.

doi:10.21608/absb.2009.7544

CONDUCTOMETRIC INVESTIGATION OF MAGNESIUM (II), CALCIUM (II) AND BARIUM (II) COMPLEXES IN AQUEOUS SOLUTION

Document Type : Original Article

Authors

¹ Chemistry Department, Faculty of Science, Al–Azhar University, Nasr City, Cairo, Egypt

² Chemistry Department, Faculty of Science, Sana'a University, Sana'a, Republic of Yemen.

10.21608/absb.2009.7544

Abstract

The ionic association constants, K_A, of Mg, Ca and Ba metal ions with succinate, malate and tartrate ligands were conductometrically determined in water at 25–40^oC. The conductometric data were analysed by the Shedlovsky extrapolation method. The K_A values tend to decrease with the cation size in the order Ca > Ba for all the salts under study with the exception of Mg salts, whereas the K_A values for the ligands increase in the order succinate < malate < tartrate. For the salts under study, standard thermodynamic functions, H^o and S^o for the association were evaluated and discussed. The positive values of both H^o and S^o in all the systems indicate the ionic association processes are the reactions of unfavorable enthalpy and favorable entropy changes in aqueous solution. The thermodynamic metal gradient, , was evaluated and its significance of ion association of all salts under investigation was discussed. On the other hand, the results of limiting molar conductance, _o, are discussed on the light of Walden product.

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