Activity coefficients of electrolyte solutions in the modified mean spherical approximation

✍ Scribed by L.M. Varela; M. Garcı́a; V. Mosquera

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 169 KB
• Volume: 323
• Category: Article
• ISSN: 0378-4371
• DOI: 10.1016/s0378-4371(03)00054-2

✦ Synopsis

The Helmholtz free energy of ionic solutions is calculated in the dressed-ion theory (DIT) using a Gibbs-Helmholtz relation. The obtained expression naturally takes into account the occurrence of a process of renormalization of charges and screening length in the bulk which is described by means of the modiÿed mean spherical approximation (MMSA). This process is shown to provoke a decreasing of the electrostatic attractions in the bulk. The chemical potentials and activity coe cients are also a matter of study and a c 3=2 dependence on molar concentration is predicted for the deviations from Debye-H uckel limiting law (DHLL) values of these magnitudes, recovering the classical results of Fowler and Guggenheim. Finally, theoretical predictions for the mean activity coe cients of 1:1 restricted primitive model (RPM) electrolytes are seen to ÿt actual hypernetted chain calculations (HNC) and ÿrst-and second-order mode expansions.