Solvation of Electrolytes and Nonelectrolytes in Aqueous Solutions

Abstract

A new theory of electrolyte and nonelectrolyte solutions has been developed which, unlike the Debye-Hückel method applicable for small concentrations only, makes it possible to estimate thermodynamic properties of a solution in a wide range of state parameters. One of the main novelties of the proposed theory is that it takes into account the dependence of solvation numbers upon the concentration of solution, and all changes occurring in the solution are connected with solvation of the stoichiometric mixture of electrolyte ions or molecules. The present paper proposes a rigorous thermodynamic analysis of hydration parameters of solutions. Ultrasound and densimetric measurements in combination with data on isobaric heat capacity have been used to study aqueous solutions of electrolytes NaNO3, KI, NaCl, KCl, MgCl2, and MgSO4 and of nonelectrolytes urea, urotropine, and acetonitrile. Structural characteristics of hydration complexes have been analyzed: hydration numbers h, the proper volume of the stoichiometric mixture of ions without hydration shells V(2h), compressibility β(1h), and the molar volume of water in hydration shells V(1h), their dependencies on concentration and temperature. It has been shown that for aqueous solutions the electric field of ions and molecules of nonelectrolytes has a greater influence on the temperature dependence of the molar volume of solution in hydration shells than a simple change of pressure. The cause of this effect may be due to the change in the dielectric permeability of water in the immediate vicinity of hydrated ions or molecules. The most studied compounds (NaCl, KCl, KI, MgCl2) have been studied in a wider range of solute concentrations of up to 4-5 mol/kg. Up to the complete solvation limit (CSL), the functions V(1h) = f(T) and β(1h) = f(T) are linear with a high correlation factor, and the dependence Y(K,S) = f(β1V1*) at all investigated concentrations of electrolytes and nonelectrolytes up to the CSL enables h and β(h)V(h) to be determined on the basis of relationships obtained in the study. The behavior of nonelectrolyte solutions is no different from that of electrolyte solutions, although it is possible to trace the difference between hydrophobic and hydrophilic interactions.

Ratiometric detection of Raman hydration shell spectra

“…The decreasing of hydration number demonstrated that Na + and NO 3 − aggregated into CIP with increasing the concentration of salt. The similar concentration dependent hydration numbers were also observed in some theoretical calculations, and the population of ion pairs were also observed to be increased with increasing the concentration in previous micro‐Raman spectra of NaNO 3 droplets . The hydration number at the concentration 0.1 M of aqueous NaNO 3 agrees with the hydration number of free NO 3 − from MD; thus, CIP is absent in the diluted concentration.…”

Analisis Termodinamika Molekul Magnesium Sulphate (MgSO4)

“…Garam mandi (61)(62)(63)(64) Kapasitas Kalor (72)(73)(74)(75) Sintesis organik (16; 76-78) Pengering (34)(35)(36)(37) Pertanian (38)(39)(40) Farmasi (18)(19)(20)(21) Elektrolit pada sintesis (85)(86)(87) Koagulan (31)(32)(33) Mobilitas Ion (65)(66)(67) Bentuk dan struktur (11; 46; 80; 81) MgSO4 umumnya dapat dijumpai dalam garam epsomite yakni MgSO4.7H2O. Di alam senyawa ini terdapat dalam bentuk mineral sulfat.…”

Temperature independence of solvation numbers of electrolytes determined by the adiabatic compression technique up to the complete solvation limit

“…In a series of works [5][6][7][8], we show that in the temperature range from 5°C to 50°C, the isoconcentration pattern…”

“…As has previously been shown, the model itself assumes the temperature independence of solvation number. Therefore, the last two options in relation (8) can be discarded as inconsistent with the model, and relation (8) takes the form…”