Thermodynamics of the amalgam cell {KxHg1 − x| KCl (m)| AgCl | Ag }and primary medium effects upon KCl in { ethylene glycol + water }, { acetonitrile + water }, and { 1,4-dioxane + water } solvent mixtures

Abstract

The electromotive force E of the amalgam cell {KxHg1−x| KCl(m)|AgCl|Ag} has been measured as a function of the mole fraction x of K metal in amalgams and of the molality m of KCl in (ethylene glycol + water), (acetonitrile + water), and (1,4- dioxane + water) solvent mixtures containing up to 0.8 mass fraction of the organic component, at the temperature 298.15 K. The respective standard electromotive forces Emohave been determined, together with the relevant activity coefficients γ±as a function of KCl molality. A new scheme is here implemented for verification of the internal consistency of the γ±results in terms of complementary pairs of concentration cells with transference. For interpolation purposes, the Emodependence on the mass fraction w of the organic component of the solvent mixture within the range explored may be expressed by:(the subscripts denoting G = ethylene glycol, A = acetonitrile, and D = 1,4-dioxane, respectively) which reproduce the observed Emovalues to within ±0.3 mV. Analysis of the relevant primary medium effects upon KCl leads to a primary hydration number of 6.6 for KCl, in good agreement with previous results based on different methods.