Terms Of Ion-solvent Interactions Research Articles

A conductivity study of dilute aqueous solutions of tetramethylammonium hexacyanoferrate(III), tetraethylammonium hexacyanoferrate(III) and benzyltrimethylammonium hexacyanoferrate(III)

Abstract Electrical conductivities of tetramethylammonium hexacyanoferrate(III), tetraethylammonium hexacyanoferrate(III) and benzyltrimethylammonium hexacyanoferrate(III) in dilute aqueous solutions, in the 278.15 K to 313.15 K temperature range are reported. These conductivities are examined in terms of the molecular model which includes an existence of three ion species in the solution, the principal cation and anion and the additional anion formed by the association between them. Based on this molecular model, the representation of conductances was performed using the Quint-Viallard conductivity equation and the Debye-Huckel expression for activity coefficients. The thermodynamic of ion pair formation is discussed in terms of ion-solvent interactions.

Partial molar volumes and viscosities of aqueous hippuric acid solutions containing LiCl and MnCl2 · 4H2O at 303.15 K

Density (ρ) and viscosity (η) of aqueous hippuric acid (HA) solutions containing LiCl and MnCl2 · 4H2O have been studied at 303.15 K in order to understand volumetric and viscometric behavior of these systems. Apparent molar volume (φv) of salts were calculated from density data and fitted to Massons relation and partial molar volumes (φ v 0 ) at infinite dilution were determined. Relative viscosity data has been used to determine viscosity A and B coefficients using Jones-Dole relation. Partial molar volume and viscosity coefficients have been discussed in terms of ion-solvent interactions and overall structural fittings in solution.

Ion association and solvation behavior of nicotinium dichromate in water-N,N-dimethyl formamide mixtures by a conductometric study

The electrical conductance of nicoitinium dichromate has been measured in water- N , N -dimethyl formamide mixtures of different compositions in the temperature range 283-313 K. The limiting molar conductance, L o and the association constant of the ion-pair, K A have been calculated using Shedlovsky equation. The effective ionic radii ( r i ) of (C 6 H 6 O 2 ) + and (C 6 H 6 O 2 NCr 2 O 7 ) - ions have been determined from L i o values using Gill’s modification of the Stokes law. The influence of the mixed solvent composition on the solvation of ions has been discussed with the help of ‘R’-factor. Thermodynamic parameters are evaluated and reported. The results of the study have been interpreted in terms of ion-solvent interactions and solvent properties.

Electrical conductance of alkali chlorides in mixed solvents : Methanol + carbon tetrachloride and methanol + 1,4-dioxane at 298.15 K

Conductance measurements for selected alkali metal chlorides, MCl (M + = Li, Na, K) are performed in the binary mixtures of methanol with carbon tetrachloride and 1,4-dioxane at 298.15 K. The limiting equivalent conductance (Λ 0 ), the association constant (K A ), and the Walden products (A 0 η 0 ) for the three salts are evaluated at all the mole fractions of the solvent mixtures using the 1978 Fuoss conductance-concentration equation. Analysis of data indicates presence of strong association of the electrolytes in the solvent mixtures studied here. The results have been discussed and interpreted in terms of ion-solvent interactions and structural changes in the mixed solvent systems.

Studies on the changes in interaction energies of salicylic acid and salicylate ion from solubility and dissociation constant measurements of salicylic acid in isopropanol+ water and t-butanol +water mixtures at 298 K

The solubilities and dissociation constants of salicylic acid in isopropanol (2-propanol) + water and t-butanol (2-methyl-2-propanol) + water mixtures have been determined. The changes in Gibbs energies of transfer of neutral salicylic acid are coupled with the changes in Gibbs energies of transfer for the dissociation processes to determine the Gibbs energy changes of transfer for salicylate ion from water to aquo-organic solvents. ΔG t (HSal - ) is positive and passes through minima at ∼34 mass% of isopropanol and ∼25 and 65 mass% of t-butanol. The results arc interpreted in terms of ion-solvent interactions and the characteristic changes in the solvent properties in these regions. In order to comprehend the ion-solvent interactions in a better way, attempts have been made to calculate the interaction energies of benzoic acid, benzoate ion, salicylic acid and salicylate ion utilizing the scaled particle theory and the data obtained from the present work and the previous works. The Gibbs energy changes due to interaction for neutral acid, ΔG t ( i n t ) water → org. solv.] are negative and favorable but ΔG t ( i n t ) due to OH group is increasingly positive indicating that OH group in the ortho-position hinders dissolution process. The ΔG t ( i n t ) (BZ - ) and ΔG t ( i n t ) (HSal - ) are positive and ΔG t ( i n t ) (BZ - ) > ΔG t ( i n t ) (HSal - ). The ΔG t ( i n t ) due to OH group in the anion is seen to he increasingly negative which can he correlated with the fact that the salicylate ion is stabilized due to hydrogen bonding leading to an increased dissociation of salicylic acid. The behavior of OH group in case of neutral acid and charged anions have been found to be exactly opposite.

Solvent Effect on the Kinetics of Oxidation of [Co(en) 2 SCH 2 CH 2 NH 2 ] 2+ by S 2 O 8 2−

The effect of the solvent on rate of the oxidation of [Co(en)2SCH2CH2NH2]2+ by S2O8 2− in aqueous mixtures of methanol (MeOH), tert-butyl alcohol (Bu t OH), acetonitrile (AN), ethylene glycol (EG) and ethylene carbonate (EC) has been analysed as regards initial and transition state contributions. From kinetic measurements and solubilities of the reactants, the Gibbs transfer functions, ΔG t°, corresponding to transfer of reactants and activated complex from water to water-organic mixtures were evaluated. The trends of the transfer functions are discussed in terms of ion-solvent interactions and the structural effects in the solvent mixtures.

Ion solvation in carbonate-based lithium battery electrolyte solutions

Partial molar volumes at infinite dilution V MX ∞ of three electrolytes (LiClO 4, LiCF 3SO 3 and LiPF 6) have been determined by vibrating-tube densimetry in pure propylene carbonate (PC), ethylene carbonate (EC) and dimethylcarbonate (DMC) and, for LiClO 4, in some mixtures of EC with DMC and PC. V mx ∞ are strongly dependent of the nature of the pure or mixed solvents. Absolute ionic molar volumes of the Li ion and associated anions have been deduced from the partial molar volume of tetra-alkylammonium salts in the same solvents. For this purpose the concept of van der Waals volume and packing density proposed by King has been employed. In all solvents under investigation, the volume of the Li ion has similar values: V Li + ∞ ≈ 5 cm 3/mol. This result is different from what is obtained using the tetraphenylarsonium tetraphenylborate assumption. The differences among polyatomic anions volumes are greater than expected and strongly dependent on the solvents' nature. These effects are discussed in terms of ion-solvent interactions: ion solvation, packing effect in the solvation shell and electrostriction. Implication of these findings for Li batteries is briefly discussed.

Conductance of selected alkali metal salts in aqueous binary mixtures of 2-methoxyethanol at 25°C

Precise conductance measurements have been performed for lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, sodium perchlorate, and sodium tetraphenylborate in 2-methoxyethanol–water mixtures at four different mole fractions, i.e., 0.056, 0.136, 0.262, and 0.486 of 2-methoxyethanol (69.73 ≥ D ≥26.55) at 25°C in the concentration range 0.0004–0.0642 mol-dm−3. The limiting molar conductivity Λ°, the association constant KA, and the association distance R for the solvent mixtures have been evaluated from the conductance concentration data using the 1978 Fuoss conductance equation. The single-ion conductances have been estimated using the “reference electrolyte” tetrabutylam-monium tetraphynylborate(Bu4NBPh4). The analysis of the data indicates that for most salts ion association is appreciable in the solvent mixtures with a mole fraction of the cosolvent of 0.262 or higher. The results have been interpreted in terms of ion-solvent interactions and structural changes in the mixed solvent media.

Partial molar volumes of tetraalkylammonium hydroxides in aqueous solution at 25°C

The densities of aqueous solutions of tetramethylammonium, tetraethylammonium, tetra-n-propylammonium and tetra-n-butylammonium hydroxide have been measured at 25°C in the concentration range 0.1–1.0 mol-kg-1 . The apparent and partial molar volumes are calculated from the density measurements. The apparent molar volumes of the solutes show considerable deviation from the Debye-Hulckel limiting law, even at high dilution. The relation for the concentration dependence of the apparent molar volume is given in an analytical form. The limiting apparent molar volumes of the solutes are split into their ionic components by an extrathermodynamic approach and are discussed in terms of ion-solvent interactions. In this way, the limiting partial molar ionic volume for the hydroxide ion is found to be 2 cm3-mol-1.

Solvation of HCI in Water-Acetone Mixtures

Activity coefficients of HCl in water-acetone mixture and thermodynamic quantities for the transfer of HCl from water to the mixed solvents at 25°C were determined by EMF measurements of the cell: H1+ glass electrode HCl in mixed solvent AgCl-Ag. These thermodynamic quantities were tentatively divided into the contribution of solvation layer consisting of solvent molecules reoriented to ions and that of the bulk region arising from the difference in dielectric constants, and the quantities of the latter were estimated from the electrostatic model by taking the value of 0.41 nm for the radius of solvated ion. The contribution of solvation layer to entropies and enthalpies of the transfer of HC1 from water to water-acetone mixture decreases with an increase in the concentration of acetone, but the contribution of solvation layer to free energies of transfer gradually increases, because of the quantities of the former being always larger than those of the latter. The thermodynamic quantities were discussed in terms of ion-solvent interactions as well as the structual changes of the solvents.

Ionization and dissociation equilibriums in liquid sulfur dioxide. 13. The behavior of singly charged spherical and planar ions

Electrolytic conductance in liquid sulfur dioxide was measured for NaI, KI, KSCN, and CsI at 273.15 K. Limiting equivalent conductances and dissociation constants were determined for these solutes by Shedlovsky's procedure. Utilizing the data of this and other investigations, we calculated thermodynamic quantities for the dissociation equilibria. Values of the Bjerrum a value, the contact distance parameter, were calculated from the equilibrium data by means of Bjerrum's equation and compared to sums of estimated ionic radii. Limiting ionic conductances based on a Fuoss-Coplan division of the limiting equivalent conductance of (i-Am)/sub 4/NB(i-Am)/sub 4/ have been evaluated. Stokes radii were calculated for the ions employed. The results obtained here for the four salts NaI, KI, KSCN, and CsI, as well as results previously published for salts containing planar ions, Ph/sub 3/CClO/sub 4/, C/sub 7/H/sub 7/Br, MePyrPc, MePyrClO/sub 4/, MePyrI, are discussed and interpreted in terms of ion-solvent interactions.

Ionic enthalpies of transfer from water to water-sulfolane mixtures

NaCl, NaBr, NaI, NaClO4, KCl, KClO4, NaBPh4, and Ph4PBr solution enthalpies were measured in water-sulfolane mixtures at 30°C. Ionic enthalpies of transfer from water to mixed solvents were calculated on the basis of the assumption ΔΔH s o (BPh 4 − )=ΔΔH s o (Ph4P+). The variation of the ionic enthalpies of transfer with solvent composition is discussed in terms of ion-solvent interactions and of the effects caused by sulfolane on the structure of water.

Variations of activity coefficients in concentrated electrolyte solutions at constant lonic strength

Measurements of different types on various (trace) electrolytes in HClO4−Na(Li)ClO4 solutions at several (constant) values of the ionic strength have been used to determine the variation of their activity coefficients with changing amount of perchloric acid in the solution. These variations (with respect to the hydrogen ion) differ considerably among different cations and anions. The results for the alkali metal ions and the anions are interpreted in the light of the recent work of Pitzer on short-range ionic interactions. The results for the cations with outerd-electrons and the alkaline earth metal ions are interpreted in terms of ion-solvent interactions. It is concluded that the use of HClO4−NaClO4 solutions of high ionic strength (rather than the use of HClO4−LiClO4 solutions) is advisable in studies where the variation in activity coefficients must be accounted for. Finally, it is shown that the usual interpretation of the influence of the salt medium in studies of complex equilibria and reaction kinetics is sometimes questionable.

Partial molal heat capacities and volumes of electrolytes in nonaqueous solvents and ion–solvent interactions

A flow heat capacity calorimeter and a flow vibrating tube densimeter have been used to measure the apparent molal heat capacities and volumes of several alkali metal and tetra-alkylammonium halides in anhydrous N,N-dimethylformamide (DMF), and the standard state partial molal heat capacities and volumes, text-decoration:overlineC0p2 and text-decoration:overlineV02, have been evaluated. A comparison of the data with similar data in water and methanol show that text-decoration:overlineC0p2 for electrolytes in the three solvents behaves quite differently. The alkali metal halides generally exhibit negative heat capacities in water and methanol and positive heat capacities in DMF at 25°C. The temperature dependence of text-decoration:overlineV02 in the three solvents is similar to that of text-decoration:overlineC0p2. Both text-decoration:overlineC0p2 and text-decoration:overlineV02 have been divided into ionic contributions and the values discussed in terms of ion-solvent interactions.

Electrode kinetics in aprotic media

Kinetic data relating to the reduction at mercury of a number of metal cations in dimethyl sulphoxide and in propylene carbonate are presented. The rate constants are discussed in terms of ion-solvent interactions.

Electrode kinetics in aprotic media

Kinetic data relating to the reduction at mercury of a number of metal cations in dimethyl sulphoxide and in propylene carbonate are presented. The rate constants are discussed in terms of ion-solvent interactions.

Effect of alkali halides on the ultrasonic absorption in D2O and H2O

Ultrasonic absorption has been studied in D2O and H2O in the presence of alkali halides in the frequency range (30/100) MHz by means of the pulse technique at 25 ‡C. The effect of salts on the viscous and the structural absorptions of both the solvents is explained in terms of ion-solvent interactions.

Solvation spectra. Part 41.—Absolute proton magnetic resonance shifts for water protons induced by cations and anions in aqueous solutions

Nuclear magnetic resonance salt shifts have been determined for a wide range of electrolytes in water at 273 and 298 K. Salt shifts for alkali metal chlorides have also been determined at 313, 333 and 353 K. Two independent methods are discussed for assigning an absolute shift to the chloride ion. The absolute values so derived are used to set up scales of absolute ionic shifts, which are discussed in terms of ion-solvent interactions. Although we do not discount the possibility of long-range effects, we can explain our results by reference only to the primary solvation layers. The anion shifts were mainly dependent on the basicity of the anion, but various anomalous cases are discussed.

Vibrational spectra of halomercurate(II) complexes in solution

The Raman spectra of solutions in acetone of crystalline salts with anionic stoicheiometries HgX3-, HgX42-, Hg2X5-, and Hg3X82- (where X = Cl, Br, or I) were determined. The dominant species identified in all cases except (pyH)2HgI4 was HgX3- which probably had a bent (C3v) configuration. The species Hg2I5- was also identified in solutions of Me4NHg.2I5. The disproportionation reactions are discussed in terms of ion-solvent interactions.

Densities and Molar Volumes of Electrolytes in Mixed Solvents

The densities of Na2SO4, MgSO4, MnCl2, NaOCOCH3, KOCOCH3, Mg(OCOCH3)2, and Ba(OCOCH3)2 have been determined at 25°C in ethanol—water and acetone—water mixtures. All the salts have been shown to follow Root's equation. The apparent molar volumes have been calculated and results interpreted in terms of ion solvent interactions and solvated molar volumes as function of the bulk dielectric constant of the solvent.