Ultrasonic vibration potentials, apparent molal volumes, and apparent molal heat capacities of 1:1 electrolytes in acetonitrile

Abstract

The ultrasonic vibration potentials and apparent molal volumes for many inorganic and organic electrolytes were measured in acetonitrile at 25°C and combined to obtain ionic contributions to the standard partial molal volumes V°(ion). Monatomic cations and anions of the same size essentially have the same V°(ion). Their size dependence can be interpreted through Hepler's equation. The apparent molal heat capacities were also measured in acetonitrile and used to derive standard values. Various methods of estimating Cp0(ion) were investigated and an ionic scale is proposed. It is concluded that Cp0(ion) of large organic ions are very close to the intrinsic heat capacities of the ions, and the solvation contribution to monatomic ions is positive for both cations and anions.