Comparison of Models for the Prediction of the Electrical Conductivity of Electrolyte Solutions

Abstract

It has been almost one century since Onsager developed the limiting law of equivalent conductivity of electrolyte solutions. Thenceforth, many models have been developed; however, they have not been assessed thoroughly and systematically. This paper comprehensively investigates the accuracy and reliability of six equivalent conductivity models, namely, the Debye–Hückel–Onsager limiting law (DHOLL), extended law (DHOEE), smaller ion shell (DHOSiS), along with the simplified and full mean spherical approximation (MSA, MSA-Simple), and Quint–Viallard (QV). To this aim, we have prepared a database of experimental data for 126 electrolytes. The accuracy of the models is examined with the help of graphical methods and error analysis over a wide range of concentrations ([0, 18] mol/L) and temperatures ([0, 100] °C). Moreover, the origin of possible errors of models is inspected with a term-by-term analysis of relaxation and electrophoretic effects. It is shown that the absolute average deviation of models depends highly on the electrolyte type, and it is generally smaller for 1:1 salts, especially at low concentrations (less than 5%). The error evolution with concentration also reveals that MSA-Simple and DHOEE are more reliable over a wide range of concentration and electrolyte types. It is concluded that MSA-Simple predicts the equivalent conductivity at lower temperatures and the trend of Λ versus T more satisfactorily than the other models.

New Electrical Conductivity Model for Electrolyte Solutions Based on the Debye–Hückel–Onsager Theory

“…It should be noted that for this comparison, the best available models reliable in a broad range of salt concentrations and temperatures in the literature has been chosen. Less accurate models spotted in our previous study have not been included in this comparison since their reliability and accuracy has been questioned previously.…”

“…This aspect will be the subject of our subsequent study, where we will delve further into the intricacies of such systems. 36 If we make the assumption of a symmetrical single salt solution, the specific conductivity of the solution is simplified to eq 42…”

“…For a comprehensive analysis of arbitrary systems of charged hard spheres that form ion pairs, an electrical conductivity model for mixed electrolytes is required. This aspect will be the subject of our subsequent study, where we will delve further into the intricacies of such systems …”

“…Among all the models developed in the literature based on the DHO theory, only the mean spherical approximation (MSA) − and the DHOSiS models assume different ion size for the prediction of the electrical conductivity. It has been shown that the DHOSiS model is only valid at very low concentrations . The MSA model, on the other hand, predicts accurately the electrical conductivity of unassociated electrolyte solutions even at high ionic strengths.…”

Ionization Difference between Weak and Strong Electrolytes as Perturbed by Conductivity Spectra Analysis

“…This behavior is usually explained by the Kohlrausch law (KL) and the Debye–Hückel–Onsager (DHO) conductivity theory for dilute solutions, which classifies the electrolytes by a degree of dissociation (Figure b). Various modifications of the Debye–Hückel theory have been developed for the past decades. ,− They extend the range of modeling to the high concentrations but still account for the dc data only.…”