Ultrasonic velocities and isentropic compressibilities of some tetraalkylammonium and copper(I) salts in acetonitrile and benzonitrile

Abstract

Ultrasonic velocities and densities of Bu₄NBPh₄, Pr₄NBPh₄, Et₄NBPh₄, Bu₄NClO₄, Pr₄NClO₄, Et₄NClO₄, Bu₄Nl, CuClO₄· 4CH₃CN and [Cu(DMPhen)₂]ClO₄ in acetonitrile and benzonitile have been measured at 298, 308 and 318 K. The isentropic compressibilities (κ_s) and apparent molal compressibilities (κ_ϕ) of various electrolytes have been evaluated. The limiting apparent molal compressibilities (κ^o_ϕ) for all electrolytes have been obtained by extrapolation of the plots of κ_ϕvs. square root of molality (m^1/2) and split into limiting ionic compressibilities (κ^o_ϕ±). κ^o_ϕ± is positive in benzonitrile except for Et₄N⁺ and is negative in acetonitrile except for Bu₄N⁺, Ph₄B^– and Pr₄N⁺. The results indicate stronger solvation of ions in acetonitrile than in benzonitrile.