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Journal of Thermal Analysis and Calorimetry
Authors: J. Galán, J. Del Castillo, A. González-Pérez, V. Fuentes-Vázquez, and J. Rodríguez

Abstract  

The specific conductivities of dodecylpyridinium chloride have been determinated in water-butanol/pentanol/hexanol solutions in the temperature range of 10 to 35C, and butanol, pentanol and hexanol concentrations up to 0.05 mol kg–1. From these data the temperature dependence of the critical micelle concentration, (cmc), was determined. The molar fraction of alcohol in the micelle was estimated using the theory suggested by Motomura et al. for surfactant binary mixtures. The standard Gibbs free energy of solubilization of alcohols in the micelles was worked out using the phase separation model.

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Abstract  

Electrical conductivity of aqueous solutions of dodecylpyridinium chloride and bromide have been determined. From these data the critical micelle concentration (cmc) was determined. The thermal properties as standard Gibbs free energy, enthalpy and entropy of micellization was estimated from a uncharged-phase separation model and enables to obtain another properties like heat capacity of micellization and the relevant parameters in the minimum of temperature dependence of cmc. The enthalpy-entropy compensation was shown for the studied compounds.

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Abstract  

The molality dependence of specific conductivity of pentadecyl bromide, cetylpyridinium bromide and cetylpiridinium chloride in aqueous solutions has been studied in the temperature range of 30–45 °C. The critical micelle concentration (cmc) and ionization degree of the micelles, β, were determined directly from the experimental data. Thermal parameters, such as standard Gibbs free energy
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enthalpy
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and entropy
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of micellization were estimated by assuming that the system conforms to the pseudo-phase separation model. The change in heat capacity on micellization
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was estimated from the temperature dependence of
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An enthalpy–entropy compensation phenomenon for the studied system has been found.
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JBU. The association equilibrium constant values, K a , as a function of free concentration of Cu 2+ , [Cu 2+ ] F , can be calculated as follows: (6) The standard Gibbs free energies as a function of Cu 2+ concentrations can be obtained as

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isotherm, and so on. The value and the sign of the standard Gibbs free energy obtained from any of the isotherm models can be used to evaluate the spontaneity of the corrosion reaction and nature of the bonding as either physisorption or chemisorption. 2

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K. The intersection of curves gives and The change in the standard Gibbs free energy and change in the standard entropy of binding could be calculated by using K a and Δ H values in Eqs. 13 and 14

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standard Gibbs free energy change ΔG° of 237 kJ/mol or 1.23 eV. The band gap energy (E g ) of the photocatalyst should be greater than 1.23 eV to achieve water splitting. However, to use visible light effectively, the band gap energy should be smaller

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