Molar Enthalpies Of Dilution Research Articles

Study on the enthalpy of solution and enthalpy of dilution for the ionic liquid [C 3mim][Val] (1-propyl-3-methylimidazolium valine)

A new amino acid ionic liquid (AAIL) [C 3mim][Val] (1-propyl-3-methylimidazolium valine) was prepared by the neutralization method. Using the solution-reaction isoperibol calorimeter, molar solution enthalpies of the ionic liquid [C 3mim][Val] with known amounts of water and with different concentrations in molality were measured at T = 298.15 K. In terms of standard addition method (SAM) and Archer’s method, the standard molar enthalpy of solution for [C 3mim][Val] without water, Δ s H m ∘ = (−55.7 ± 0.4) kJ · mol −1, was obtained. The hydration enthalpy of the cation [C 3mim] +, Δ H + ([C 3mim] +) = −226 kJ · mol −1, was estimated in terms of Glasser’s theory. Using the RD496-III heat conduction microcalorimeter, the molar enthalpies of dilution, Δ D H m( m i → m f), of aqueous [C 3mim][Val] with various values of molality were measured. The values of Δ D H m( m i → m f) were fitted to Pitzer’s ion-interaction model and the values of apparent relative molar enthalpy, φL , calculated using Pitzer’s ion-interaction model.

Enthalpy of Dilution of Aqueous [C4mim][Gly] at 298.15 K

A novel amino acid ionic liquid [C4mim][Gly] (1-butyl-3-methylimidazolium glycine) was prepared by a neutralization method. The molar enthalpies of dilution, ΔDHm(mi→mf), of aqueous [C4mim][Gly] at various molalities were measured at (298.15 ± 0.01) K. The values of the apparent relative molar enthalpy, φL, were calculated by using both the extended Debye−Huckel equation and the Pitzer equation, which were in good agreement within experimental error. In terms of φL, the molar enthalpies of solution of [C4mim][Gly], ΔsHm, at various molalities were estimated. The estimated values of ΔsHm were consistent with the experimental values previously obtained.

Enthalpies of dilution of mono-, di- and poly-alcohols in dilute aqueous solutions at 298.15 K

Abstract The enthalpies of dilution of aqueous solutions of methanol, ethanol, l-propanol, 2-propanol, 1-butanol, l-pentanol, 1-hexanol, cyclohexanol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol and poly-alcohol(cyclohexaamylose) have been determined at high dilution as a function of the mole fraction of alcohol at 298.15 K, by a rocking twin-microcalorimeter of the heat-conduction type. A smoothing equation of the enthalpies of dilution against the mole fractions of alcohols are given. The graphical comparison of experimental results with their smoothed values or literature ones, taking into account the dependence of the mole fractions, are also presented. It has been found for the aqueous solutions of shorter n-alcohols than hexanol that at very high dilution, exothermic values of molar enthalpies of dilution from a definite mole fraction of alcohols to infinite dilution with the change of mole fraction is proportional to carbon number of n-alcohols. The molar enthalpies of infinite dilution of aque...

The enthalpy of dilution and apparent molar heat capacity of NaOH(aq) to 523 K and 40 MPa

The molar enthalpy of dilution Δ dil H m of NaOH(aq) was measured from 6.3 to 0.008 mol · kg −1 at temperatures from 298 to 523 K and pressures from 7 to 40 MPa with a differential flow mixing enthalpy calorimeter. Apparent molar heat capacities C p, φ were measured with a flow heat-capacity calorimeter from 4.0 to 0.1 mol · kg −1 from 323 to 523 K at 7 MPa. These results are correlated with available literature values as functions of temperature, pressure, and molality with the ion-interaction thermodynamic treatment. The extended form of the ion-interaction model, including an approximation for the effect of ion association, was needed to represent the enthalpy results quantitatively above 473.15 K; this additional term does not have a large effect on the activity or osmotic coefficients. Standard heat capacities calculated from this work are consistent with literature values for the heat-capacity change on ionization of water.

Enthalpies of dilution of aqueous electrolytes: The NaCl/H2O system

Analysis of enthalpy of dilution data for the system NaCl/H2O at 298.15°K with correlating equations presently in widespread use shows that these do not satisfactorily fit the data at the lowest available concentrations. A new approach based on the extended Debye-Huckel theory is suggested. It is shown that a plot of the ratio of the apparent molar enthalpy of dilution to the change in ionic strength, ΔϕL/ΔI, versus (I i 1/2 −I f 1/2 )/ΔI, should give a straight line at low enough concentration with a slope 2SH/3. The intercept is related to the Debye distance parameterA′ and the coefficient of the first virial correction term. The quantitySH is the limiting Debye slope as calculated from the properties of the pure solvent. These expectations are substantiated by the fits. Values of the parameters are compared with older estimates, and it is concluded that the choiceA′=0 is reasonable.