Thermochimica Acta, 140 (1989) 7-11 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands zyxwvutsrqponmlkjihgfedcb STUDY OF THE Ph,SbBPh, ASSUMPTION FOR SINGLE ION FREE ENERGIES IN SOME ORGANIC SOLVENTS ESAM A. GOMAA * Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt) (Received 24 February 1988) ABSTRACT A critical study has been carried out to verify the Ph,SbBPh, electrolyte assumption, in which the standard free energies of transfer of the electrolyte AG* from one solvent to another are divided equally between the cation and the anion. A discussion is presented on the basis of a model which treats the total solvation energy of an ion as a composite of electrostatic and non-electrostatic contributions. The neutral molecules Ph,Sn and Ph,C, are proved to be (from their sizes and structures) neutral analogues of the reference ions Ph$b+ and Ph,B-, respectively. The single free energies of the reference ions Ph$b+ and Ph,B- were also estimated. On plotting the relationship between the free energies of transfer of Ph,SbBPh, against Gutmann’s acceptor and donor numbers, good agreement was obtained, indicating the similarity of the electrostatic charges on the two reference ions. INTRODUCTION zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB The estimation of single ion free energies requires extra thermodynamic assumptions, for which a wide variety of methods have been introduced. The existing methods have been continuously discussed by a number of workers [l-6] and most extensively by Parker [2] and Popovych [3]. The methods [7-lo] that have been used most extensively for single ion thermodynamic determination are based on the assumption that the thermodynamic values for a large reference cation can be equal to those of a reference anion of molecular similarity. Different pairs of large reference ions have been suggested, i.e. TABPh,B (TAB, triisoamyl-n-butylammonium) [ll] and Ph,AsBPh, [12]. It has been proved by Kim [13,14] that Ph,A sBPh, is an asymmetric model. The aim of this work is to study the plausibility of Ph,SbBPh, electrolyte for single ion thermodynamic determination. * Present address: Teachers Training College, Salalah-P.O.19905, Sultanate of Oman. 0040-6031/89/$03.50 0 1989 Elsevier Science Publishers B.V.