Solubility of inert gases and liquid hydrocarbons in water
- Univ. of Parma (Italy); and others
The thermodynamic statistical model based on the distribution of molecular populations among energy levels has been employed for the analysis of the solubility of hydrocarbons and other inert gases or liquids in water at different temperatures. The statistical distribution is described by a convoluted partition function Z{sub G}{center_dot}{zeta}{sub s}. The product of a grand canonical partition function Z{sub G} represents the distribution of the species in the reaction while the canonical function {zeta}{sub s} represents the properties of the solvent. The first derivative of the logarithm of the partition function with respect to 1/T is the apparent enthalpy which is the result of the contributions of the separate partition functions, [{Delta}H{sub app}]{sub T} = {Delta}H{degrees} + n{sub w}C{sub p,w}T, where [{Delta}H{sub app}]{sub T} refers to Z{sub G}, n{sub w}C{sub p,w}T = -{Delta}H{sub w} to {zeta}{sub s}, and {Delta}H{degrees} is the change in enthalpy of hydrocarbon-water reaction. The plot [{Delta}H{sub app}]{sub T} vs. T results in a straight line with slope n{sub w} at constant C{sub p,w}. The apparent enthalpy is obtained from the coefficients of the polynomial fitting of the solubility data, as a function of 1/T. Alternatively, the apparent enthalpy can be determined calorimetrically. The enthalpy thus obtained is a linear function of the Kelvin temperature. The values of n{sub w} range from 1.6, 1.9, 5.6 to 5.8 for helium, hydrogen, butane and hexane, respectively. For fluorocompounds the range of n{sub w} is 10.1 to 11.1 indicating that n{sub w} is a function of the number of water molecules expelled from the cage of solvent to form a cavity to host the solute molecule. The analysis of several sets of calorimetric or solubility data with the present molecular thermodynamic model yields values of {Delta}H{degrees} and n{sub w} consistent with the size of the dissolved molecules.
- OSTI ID:
- 245499
- Journal Information:
- Journal of Solution Chemistry, Vol. 24, Issue 7; Other Information: PBD: Jul 1995
- Country of Publication:
- United States
- Language:
- English
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