Limiting Conductances of Electrolytes and the Walden Product in Mixed Solvents in a Phenomenological Approach

Abstract

The applicability of the Quint-Viallard conductivity equation to the representation of electrical conductivities in mixed solvents is examined. The concept of the modified Walden product is introduced, and the benefits compared with the ordinary Walden product are discussed. The universal curve of limiting conductances for all electrolytes (or for all ions) in a given pair of solvents is introduced and examined in a number of mixtures which include methanol, ethanol, 1-propanol, tert-butyl alcohol, 1,4-dioxane, N, N-dimethylformamide, sulfolane, tetrahydrofuran, and ethylene carbonate with water. Also examined are nonaqueous mixtures of acetone-ethanol, acetone-1-propanol, dimethyl sulfoxide-propylene carbonate, acetonitrile-methanol, acetonitrile-carbon tetrachloride, and acetonitrile-propylene carbonate. Many electrolytes were involved in the evaluation of the universal curves, but the majority are alkali-metal halides, tetraalkylammonium halides, tetraalkylammonium tetraphenylborides, and potassium xanthates (inorganic and organic acids are treated separately). If in a given mixed solvent system the limiting conductance of electrolyte is unknown, the universal curve permits estimating its value and gives an indication about the quality of performed conductivity measurements. The existence of universal curves of limiting conductances indicates that the properties of electrolytes in pure solvents are, to a great extent, preserved also in the mixture of solvents due to the simple dilution effect.

Densities, Viscosities [from (278.15 to 318.15) K], and Electrical Conductivities (at 298.15 K) of Aqueous Solutions of Choline Chloride and Chloro-Choline Chloride

“…Since the values obtained for the h parameter of eq suggest only weak ion association it is therefore surprising to find a rather large decrease of Λη with increasing m for both ChCl(aq) and Cl-ChCl(aq) (Figure ). However, it should be kept in mind that also changes in ion solvation with rising concentration may cause deviation from Walden's rule . To clarify this issue, dielectric relaxation studies are currently under way to obtain molecular-level information on ion hydration and association in these systems.…”

Interplay of Ion-Specific and Charge-Density Effects in Aqueous Solutions of Weakly Charged Ionenes as Revealed by Electric-Transport Measurements

“…This trend mostly results from the fact that the viscosity of water, η, decreases with increasing temperature. According to Walden’s rule, , the product of the viscosity of the solvent and the conductivity of a solution, ηΛ, for a particular salt should be approximately constant at all temperatures (note that strictly speaking Walden’s rule is defined at infinite dilution). For ionene solutions studied here, Walden’s rule is only approximately satisfied (see Figures S5 and S6 in the Supporting Information).…”

Diffusion coefficients and electrical conductivities for calcium chloride aqueous solutions at 298.15K and 310.15K

“…Table 5. Another way to obtain this limiting value at 310.15 K is from the Walden product (or Walden rule): 0 (T) Á(T) = cte, being Á(T) the viscosity of the pure solvent at temperature T. Recently, Apelblat has extensively illustrated, by using different electrolytic solutions [20], the usefulness of this empirical relationship, which considers the changes of the solvent viscosity are the responsible of the changes in the conductivity of the ions. From it, a value of 350.12 × 10 −4 m 2 mol −1 −1 was estimated by using 0.8903 (cP) and 0.6909 (cP) for the viscosity of pure water at 298.15 K and 310.15 K, respectively [21].…”