The apparent molal volumes of 29 electrolytes have been determined in the medium 0.725 m NaCl from precise density measurements at 25°C. The values of φV have been extrapolated to infinite dilution by using a least-squares fit of the data and by using Young's rule. The two methods yield values of V̄*0 in 0.725 m NaCl that agree to within 0.2 cm3 mol-1. The experimentally determined values of V̄*0 are compared to those predicted from binary solution data by using the ionic strength principle, Young's rule, and the specific interaction model. The values of V̄*0 predicted by using the specific interaction model and Young's rule are similar and in better agreement (±0.3 cm3 mol-1) with the experimental results than those predicted by using the ionic strength principle (±0.4 cm3 mol-1). For electrolytes without a common cation (Na+) or anion (Cl-), the specific interaction model gives the best estimates. The volumes of mixing the electrolytes with a common cation (NaX + NaCl) and anion (MCl + NaCl) at I = 0.725 determined from our results correlate very well with the enthalpies of mixing and various properties of the uncommon ion (M+ and X-).
ASJC Scopus subject areas
- Physical and Theoretical Chemistry