Partial molar volume studies of ion-solvent interactions in some mixed solvent media

Abstract

Partial molar volumes <i>φ</i>_v of sodium chloride, sodium acetate, sodium formate, hydrochloric acid, acetic acid and formic acid have been determined dilatometrically in some quasi-isodielectric [water (W) + cosolvent (aprotic dioxane (D), dipolar aprotic (DMF) and protic (FO)] media at 308.15 K and the same have been analysed to evaluate their limiting <i>φ</i><img src='http://www.niscair.res.in/jinfo/equation33.gif' border=0> values. These values have been coupled with the corresponding limiting values in W to compute <img src='/image/spc_char/delta.gif' border=0><i>φ</i><img src='http://www.niscair.res.in/jinfo/equation33.gif' border=0> data which suggest that for a particular HA or NaA, the <img src='/image/spc_char/delta.gif' border=0><i>φ</i><img src='http://www.niscair.res.in/jinfo/equation33.gif' border=0> values generally vary as FD < DMF < D as required by the Gutmann's donor and the electron pair acceptance indices of formamide (FO), N,N-dimethylformamide (OMF) and 1,4-dioxane (D) cosolvents in the present mixed solvent media. The variation of <img src='/image/spc_char/delta.gif' border=0><i>φ</i><img src='http://www.niscair.res.in/jinfo/equation33.gif' border=0> (HA or NaA) within the same mixed solvent media suggest that while the chemical effects of protons of acids on the cosolvent have a dominant influence (based on Ben-Naims approach) on their <img src='/image/spc_char/delta.gif' border=0><i>φ</i><img src='http://www.niscair.res.in/jinfo/equation33.gif' border=0>; data, the electrostriction effects of CH)COO^-, HCOO^- and Cl^-on W play an important role in determiningthe values of <img src='/image/spc_char/delta.gif' border=0><i>φ</i><img src='http://www.niscair.res.in/jinfo/equation33.gif' border=0> of their sodium salts.