Standard potentials of the silver–silver chloride electrode in t-butyl alcohol–water mixtures and the thermodynamics of solutions of hydrochloric acid at different temperatures

Abstract

Electromotive force measurements of cells of the type Pt.H, (g, 1 atm)IHCl(m), ButOH (X),H,O(lOO -X)lAgCl-Ag at 5,15, 25, 35, and 45 "C have been used to evaluate (i) the standard potentials of the Ag-AgCI electrode for X = 10, 20. 40, and 70% (w/w) by a polynomial curve-fitting technique, (ii) the mean molal activity coefficients of hydrochloric acid (0.005-0.2 mol kg-l), (iii) the primary medium effects, (iv) the relative partial molal enthalpies, and (v) the thermodynamic functions for the transfer of HCI from water to the respective solvent media. The values of Emo in each solvent have been represented as a function of temperature. The significance of the results has been discussed in relation to the acid-base properties and the breakdown of the structure of water on the addition of t-butyl alcohol.THE behaviour of electrolytes in aqueous organic mix-tures1-3 is of interest. We chose the binary water-tbutyl alcohol solvent mixtures because these media are frequently used for studies of colloid science,* chemical equilibria,6 viscosity and diffusion coefficients,6 and also in the investigation of electronic transitions.' To our knowledge no potentiometric investigation has been made on the effect of these solvent mixtures in the study of acid-base equilibria.

Computational Techniques of Ionic Processes in Water—Organic Mixed Solvents

“…Thus -AG° = 1SSFE 0 (14) in which E°, the standard potential, is expressed by S° -£obs + ~ In m + ?ψ· lny± (15) with Eob8 being the measured potential of the working Cell I. It should be emphasized here that the standard cell is an imaginary device in which m = a = y± = 1.…”

Ion selective electrodes, potentiometry, and potentiometric titrations

“…The Feakins group has studied transport and free energies of solvation in MeOH-H20 (266)(267)(268). Acidity scales, buffers, and halide reference electrode behavior have been investigated in MeOH-H20 (628,732,911), EtOH-H20 (564, 829-831), methoxyethanol-H20 (792), iso-PrOH-H20 (643,851), <er<-BuOH-H20 (643, (813), Et0H-benzene-H20 (10), glycolic solvents (509, 827), DMS0-H20 (25,473,474), and methylpyrrolidone-tetramethylene sulfone-H20 (583). Free energies of transfer of KC1 between water and EtOH, dioxane and acetone-H20 mixtures have been measured by De Ligny's group (65).…”

Thermodynamics of transfer of hydrogen chloride in water-dimethylformamide mixtures from electromotive force measurements

“…The emf data for the cell 1 in various solvent mixtures corrected for a partial pressure of 1 atm of hydrogen are given in Table II. The standard molal potentials, s£°m, of the cell in the various solvent mixtures were determined by the extrapolation of the function above equation K = RT In 10/F, m is the molality of HCl (mol kg"1), A'and B' are the Debye-Hückel constants on the molal scale, a is the ion size parameter (A), b is the coefficient occurring in the expression for activity coefficient as a function of molality, and is the mean molecular weight of the solvent defined as = 100/{x/Mx + y/My) (3) where x and y are the weight percentages of DMF and water, respectively, and Mx and My are the corresponding molecular weights. In the determination of sE°m, a = 5 A was used in all compositions, as this was found to give good linear plots with the least slope.…”

“…Electromotive force measurements on galvanic cells employing hydrogen and silver-silver halide electrodes have been widely used in recent years (1)(2)(3)(4)(5)(6)(7)(8)(9) to determine the thermodynamics of hydrogen halides in aqueous, mixed aqueous and nonaqueous media. Such studies enable us to understand the electrolyte-solvent interactions and also to evaluate the thermodynamics of ion-solvent interactions employing suitable extra thermodynamic assumptions.…”