Standard molar entropy

About: Standard molar entropy is a research topic. Over the lifetime, 1586 publications have been published within this topic receiving 29886 citations.

Adsorption of 1-Monoglycerides at the Hexane/Water Interface.

Abstract: The interfacial tension of a hexane solution of 1-monolaurin against water was measured as a function of temperature and concentration under atmospheric pressure. The thermodynamic quantity changes associated with the adsorption of 1-monolaurin were evaluated and compared with those of the previously reported 1-monomyristin. The decrease of two carbon atoms in the hydrocarbon chain results in a slight expansion of the 1-monolaurin adsorbed film and in a slight decrease in entropy and energy changes compared with those of the 1-monomyristin system. The large negative value of the entropy change at a high concentration is related to the restricted orientation of the polar head group of 1-monolaurin at the hexane/water interface due to the strong interaction between the large hydrophilic group of 1-monolaurin and the water molecules, as in the 1-monomyristin system. The origin of the distinction in the entropy change behavior between the adsorption from the hexane phase and water phase was discussed. The usefulness of an easier calculation process for the partial molar entropy change is verified by comparison with the usual reliable value and with the entropy of adsorption.

Potentiometric Study of Intermolecular Interactions in Cationic-Nonionic Mixed Surfactant Systems

Abstract: The nature and thermodynamics of interactions of the cationic surfactant dodecyltri methylammonium bromide (DTA) with the nonionic surfactant Triton X-100 (TX100) in mixtures are studied using the potentiometric method. We investigate the influence of temperature, the addition of KBr, and the concentrations of DTA and TX100 on the complex formation between free DTA cations and TX100 nonionic micelles in solution. Binding isotherms, distribution coefficients Kx, and stoichiometric equilibrium constants K1 are determined from the experimental data. The standard free energy change (ΔG1°), the standard enthalpy change (ΔH1°) and the standard entropy change (ΔS 1°) are calculated for transferring the free DTA cation from the aqueous bulk phase to the TX100 nonionic micelle phase. Our results support the assumption that hydrophobic interactions are the most important in this binding process.

Thermodynamic properties of copper-nickel alloys: measurements and assessment

Abstract: The activity of Ni in solid Cu-Ni alloys was measured at 1000 K using a solid state galvanic cell incorporating CaO-stabilized $ZrO_2$ as the solid electrolyte. The activity of Ni shows positive deviation from Raoult's law over the entire range of concentration. Partial molar entropy of Ni in solid Cu-Ni alloys was measured directly using a newly developed twin solid state thermocell apparatus. A consi-stent set of thermodynamics data for the Cu-Ni system was derived by combining the results of the present study with selected data on enthalpy and free energy of mixing of liquid alloys and the phase diagram. The miscibility gap and the chemical spinodal boundaries obtained from the evaluated data are in good agreement with x-ray & diffuse neutron scattering studies reported in the literature.