Ion association and solvation in solutions of Mg 2 + , Ca 2 + , Sr 2 + , Ba 2 + and Ni 2 + perchlorates in acetonitrile: Conductometric study

Abstract

Conductance data for perchlorates of Mg 2 + , Ca 2 + , Sr 2 + , Ba 2 + , and Ni 2 + in acetonitrile solution at 5, 15, 25, 35, 45 and 55 °C are reported. Data were treated by using extended Lee-Wheaton equation. The total limiting equivalent conductivities ( Λ eq 0), and the first step (primary) association constants ( K A I ), were derived. The primary association constants, K A I (KtClO 4 +), and their temperature dependences are discussed in terms of contact and solvent separated ion pairs and the role of non-Coulombic forces caused by cation solvation. The single limiting equivalent conductivities ( λ eq 0) of 1 2 Kt 2 + (Kt = Mg, Ca, Sr, Ba and Ni), ClO 4 – and KtClO 4 + in acetonitrile were evaluated from Λ eq 0 and conventional transference number of 1 2 Kt 2 + obtained in the framework of the developed method of conductometric data processing. Variation in λ eq 0 were interpreted in terms of spatial-time ion-molecular correlations in the nearest environment of solvated ions.