Study of the Comparative Solvation Behaviour of Na⁺ and Cu⁺ Cations in Acetonitrile + N,N-Dimethylformamide Mixtures at 298.15 K

Abstract

Viscosity and molar conductance of Bu 4 NBPh 4 , Bu 4 NClO 4 , [Cu(CH 3 CN) 4 ]ClO 4 , NaClO 4 and NaBPh 4 have been measured in the concentration ranges 0.02 - 0.5 mol dm −3 and 0.0005 - 0.0065 mol dm −3 at 298.15 K in AN + DMF mixtures containing 0, 10, 20, 40, 60, 75, 80, 90, and 100 mol % DMF. The viscosity data have been analyzed by the extended form of the Jones-Dole equation in the form: (η/η0) = 1+AC 1/2 +BC+DC 2 to evaluate B and D parameters and the conductance data by the Shedlovsky equation to evaluate Λ o and K A values of the salts. Ionic viscosity B-coefficients (B ± ) and ionic molar conductances (λ◦ i ) have been calculated by using Bu 4 NBPh 4 as a reference electrolyte. Solvated radii (r i ) for Na + , Cu + and ClO 4 − have been estimated by using Gill’s modification of Stokes’ law. The variation of B ± and r i as a function of mol % DMF shows that both Na + and Cu + are highly solvated in AN + DMF mixtures over the entire composition region. The solvation passes through a maximum between 40 to 80 mol % DMF. Both Na + and Cu + are more strongly solvated between 40 to 80 mol % DMF. Cu + is relatively more strongly solvated than Na + in AN + DMF mixtures. ClO 4 − shows poor solvation in AN + DMF mixtures.