Transport and compressibility studies of some copper(I) perchlorates in binary mixtures of benzonitrile and acetonitrile

Abstract

Transference numbers of ClO^–₄ and Cu⁺ ions in copper(I) perchlorate have been measured in the concentration range 0.02–0.22 mol dm^–3 in benzonitrile(BN)–acetonitrile(AN) mixtures at 298 K by the modified Hittorf method. The limiting transference numbers of Cu⁺(t^o+_Cu) in various solvent systems were evaluated by the modified Longsworth method. Molar conductances, ultrasonic velocities and densities of CuClO₄· 4CH₃CN and [Cu(DMPhen)₂]ClO₄ were measured at 298 K in BN–AN mixtures. The limiting molar conductances (Λ_o) of the electrolytes were obtained by analysis of the conductance data using the Shedlovsky equation. Limiting ionic conductances (λ^o_i) for Cu⁺, [Cu(DMPhen)₂]⁺ and ClO^––₄ ions and hence their solvated radii (r_i) were calculated. The variation in solvated radii of ions as a function of solvent composition showed no preferential solvation of any ion by AN or BN. From the ultrasonic velocity and density measurements, the isentropic compressibilities (κ_s) and the limiting apparent molal isentropic compressibilities (κ^o_ϕ) for CuClO₄· 4CH₃CN and [Cu(DMPhen)₂] ClO₄ were evaluated. That κ^o_ϕ values for the copper(I) salts became less negative or more positive with increasing BN mole fraction indicating that both these copper(I) salts are structure makers in AN and that the structure-making tendency of the salts decreased with increasing BN mole fraction.