Thermodynamics of the cell {Li-amalgam|LiX(m)|AgX|Ag} (X = Cl, Br) and medium effects upon LiX in (acetonitrile + water), (1,4-dioxane + water), and (methanol + water) solvent mixtures with related solvation parameters

The electromotive forces E of the amalgam cells {LixHg1-x|LiCl(m)AgCl|Ag} and {LixHg1-x|LiBr(m)|AgBr|Ag} were measured as a function of the mole fraction x of Li metal in amalgams and of the molalities m of LiCl as well as LiBr at T = 298.15 K. For LiCl, the solvents studied were (acetonitrile + water), (1,4-dioxane + water), and (methanol + water) mixts. contg. up to mass fraction 0.8 of the org. component, but only (acetonitrile + water) mixts. for LiBr. The std. molal electromotive forces Emo were detd. and, for all the solvent systems explored, they appear to vary linearly with the mole fraction y of the org. component involved, according to the following equations: Emo(LiCl)/V = 2.4169-0.2961yA; Emo(LiCl)/V = 2.4175-0.5951yD; Emo(LiCl)/V = 2.4163-0.1749yM; Emo(LiBr)/V = 2.2672-0.2092yA, where A denotes acetonitrile, D is 1,4-dioxane, and M is methanol. The relevant mean molal activity coeffs. as functions of the LiCl and LiBr molalities also were detd. The primary medium effects upon LiCl and LiBr, analyzed in terms of the Feakins-French theory, lead to primary hydration nos. of ≈5 for LiCl and ≈4 for LiBr. These are somewhat lower than those obtained by other methods, but their difference is expected considering the known primary hydration nos. of the anions Cl- and Br-.