Thermodynamic Studies on Ion Association of Lithium Chloride and Lithium Nitrate in Acetonitrile + Water Mixed Solvents at Different Temperatures

The present study reports the ion association of lithium chloride (LiCl) and lithium nitrate (LiNO3) electrolytes in acetonitrile + water (AN+W) mixtures at 283.15 K to 311.15 K. Their limiting molar conductance (Λo), the association constant values (KA) for their different mole fractions, i.e. 0.0000, 0.0588, 0.1233, 0.1942, 0.2727, 0.3600, 0.4576, 0.5676, 0.6923, 0.8351 and 1.0000 have been evaluated using Shedlovsky technique. The KA and Walden products (Λoηo) for LiCl and LiNO3 salts have been calculated in the acetonitrile-water solvent at experimental temperatures. The calculated values qualitatively examined the possible nature of the solvent-solvent, their ion-ion, and ion-solvent and interactions of the two selected compounds mixed solvents of (acetonitrile + water). Then dependence of KA temperature has also been investigated to obtain the thermodynamic functions of different parameters, such as ΔGº, ΔSº, ΔHº and Ea, as a function of the mixed composition of the composition solvents AN+W (acetonitrile + water).

Electrochemical behaviour of the Zn(II)–Zn(Hg) system in aqueous ethylene glycol solutions

The electrochemical behaviour of the Zn(II)–Zn(Hg) system in aqueous ethylene glycol (EG) solutions containing 5.0 × 10−2 M LiClO4 has been studied by polarography and cyclic voltammetry. The reversible half-wave potentials, the diffusion coefficients and the Walden products for Zn(II) have been polarographically determined. The standard free energies of transfer of 1 mol of Zn(II) ions from water to EG–water mixtures, [Formula: see text], obtained from the reversible half-wave potentials vs. the ferrocene electrode scale, are always negative, indicating a greater stability of Zn(II) in EG–water mixtures than in pure water. The splitting of the [Formula: see text] values into electrostatic and chemical contributions shows that the mixtures are more basic than water. The analysis of the variation of the Walden product with solvent composition indicates an enhancement of the solvent structure in the water-rich region. The diffusion coefficient for Zn in mercury, the transfer coefficients for Zn(II) electroreduction, and the apparent standard rate constants of the Zn(II)–Zn(Hg) system have been determined by cyclic voltammetry. The change in the kinetics with solvent composition is discussed in terms of existing models.

Conductance studies in amide–water mixtures. VI. Nitrates of sodium, potassium, and ammonium in N,N-dimethylformamide–water mixtures at 25 °C

Conductance data for the nitrates of sodium, potassium, and ammonium in N,N-dimethylformamide (DMF) – water mixtures (74.39 ≥ D ≥ 36.11) at 25 °C are reported for the concentration range 0.0003–0.06 mol dm−3. Also densities, viscosities, and dielectric constants of the solvent mixture (DMF–water) are reported at the same temperature. The data have been analysed by the Fuoss (1978) equation excluding the term α. The existence of a maximum in the viscosity at a 1:3 mol ratio of DMF and water is attributed to the formation of a solvated complex DMF•3H2O. The Walden products for all the three salts pass through a maximum while the equivalent conductances show a minimum with the change of DMF content in the solvent mixtures. In any given solvent mixture, the limiting equivalent conductances show the trend NaNO3 < KNO3 < NH4NO3. The existence of a maximum in Walden product is attributed to the dehydration of ions due to presence of the cosolvent (DMF). For all the three salts, the association constant was negligible (KA < 10) in all the solvent mixtures studied.