Excess partial molar entropy of alkane-mono-ols in aqueous solutions at 25°C

In the preceding paper, we reported the values of model-free chemical potentials for aqueous methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-hexanol at 25°C over the entire compositional region. Using alcohol excess partial molar enthalpies, HEAL, determined earlier in this laboratory (Can. J. Chem. 74, 713 (1996)), we have calculated excess partial molar entropies for the alcohols, SEAL, where AL stands for an alcohol. We then calculated, numerically, the entropic interaction, SEAL–AL = N([Formula: see text]SEAL/[Formula: see text]nAL)p,T,nW, where nAL is the amount of AL, nW is the amount of H2O, and N is the total amount of solution. SEAL–AL signifies the effect of addition of AL upon the entropic situation of existing AL in solution. Using these quantities, the mixing schemes in aqueous alcohols have been studied. The earlier conclusions, which used HEAL and HEAL–AL alone, are confirmed. Furthermore, the order of the relative hydrophobic nature of alcohols is established from the behaviour of SEAL–AL and of HEAL–AL as methanol < ethanol < 2-propanol < 1-propanol. Key Words: aqueous alcohols, excess partial molar entropies, entropic interaction mixing schemes, hydrophobicity ranking.

Thermodynamic stability field of the 123 and 124 phases in the Y2O3–BaO–Cu–O system

The partial molar entropy of solution of oxygen in YBa2Cu3Ox, δsO, has been computed using equilibrium data and the recently measured partial molar enthalpy of oxygen. While δhO is independent of oxygen content (6 < x < 7), δsO depends on x. The po2, T location of phase equilibrium between the 123 and 124 superconducting phases is calculated. The standard free energies of interactions of the superconducting phases with carbon dioxide (CO2) and water vapor (H2O) have been assessed. The free energies of carbonation of the fully oxidized 123 and 124 phases are −323 ± 22 kJ mol−1 and −291 ± 32 kJ mol−1, respectively. The free energies of hydration of the 123 and 124 are −397 ± 22 kJ mol−1 and −469 ± 32 kJ mol−1, respectively. These large exothermic values show that degradation of these superconductors at ambient conditions is thermodynamically favorable.