scholarly journals Thermal expansivities of aqueous solutions of 2-butoxyethanol in the water-rich region: transition of mixing scheme

1992 ◽  
Vol 70 (10) ◽  
pp. 2659-2663 ◽  
Author(s):  
James V. Davies ◽  
Frankie W. Lau ◽  
Loanne T. N. Le ◽  
John T. W. Lai ◽  
Yoshikata Koga
Keyword(s):  
Free Energy ◽  
Aqueous Solutions ◽  
Gibbs Free Energy ◽  
Rich Region ◽  
Hydrophobic Solute ◽  
Thermal Expansivities ◽  
Mixing Schemes ◽  
Structure Enhancement ◽  
Derivatives Of ◽  
Transition Of Mixing Scheme

Thermal expansivities of aqueous solutions of 2-butoxyethanol (BE) were measured at concentrations of xBE < 0.04, where xBE is the mole fraction of BE. Thermal expansivity is a second derivative of the Gibbs free energy. The composition derivatives of thermal expansivities, the third derivatives, show peak anomalies at the same loci as the other third derivatives of the Gibbs free energy reported earlier from this laboratory (Can. J. Chem. 67, 671 (1989); J. Phys. Chem. 94, 3879 (1990); J. Phys. Chem. 95, 4119 (1991)). The loci of such anomalies form a boundary that separates two regions of totally different mixing schemes. The mixing scheme in the water-rich region seems to be consistent with the "iceberg formation," the "structure enhancement of H2O by hydrophobic solute," and the "hydrophobic attraction." In the intermediate composition region, the hydrogen bond network of H2O collapses due to the presence of too many molecules of BE, and H2O and BE molecules interact with each other as normal liquid molecules.

Ionic conductivity in the water-rich region of aqueous 2-butoxyethanol

1995 ◽  
Vol 73 (8) ◽  
pp. 1294-1297 ◽  
Author(s):  
Yoshikata Koga ◽  
Virginia J. Loo ◽  
Kataryna T. Puhacz
Keyword(s):  
Hydrogen Bond ◽  
Ionic Conductivity ◽  
Aqueous Solutions ◽  
Infinite Dilution ◽  
Ionic Conductivities ◽  
Molar Conductivity ◽  
Hydrogen Bond Network ◽  
Rich Region ◽  
Mixing Schemes ◽  
Bond Network

Ionic conductivities of HCl, KOH, and KCl were measured in aqueous solutions of 2-butoxyethanol (BE) at 25 °C. The quantity, Λj′ = σ/xj, which is almost proportional to the molar conductivity, was extrapolated to the infinite dilution xj → 0. σ is the conductivity and xj is the mole fraction of j(= HCl, KOH, or KCl). The plots of 0Λj′, the value of Λj′ extrapolated to infinite dilution, against xBE showed a change in slope at xBE = 0.0175. The previous work from this laboratory indicated that the mixing scheme changes qualitatively at the same locus, xBE = 0.0175. By mixing scheme we simply mean the way in which BE and H2O molecules mix with each other. Assuming additivity in 0Λj′ in terms of constituent ions, those values for H+OH− were calculated. Plots of [Formula: see text] thus calculated as a function of xBE in the water-rich region, 0 < xBE < 0.0175, suggest that the hydrogen bond probability decreases in the bulk of solution, as xBE increases. Keywords: aqueous 2-butoxyethanol, ionic conductivities, mixing schemes, hydrogen bond network.

scholarly journals Excess partial molar enthalpies of alkane-mono-ols in aqueous solutions

1996 ◽  
Vol 74 (5) ◽  
pp. 713-721 ◽  
Author(s):  
Steven Hiroshi Tanaka ◽  
Hikari Infinity Yoshihara ◽  
Alice Wen-Chi Ho ◽  
Frankie W. Lau ◽  
Peter Westh ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Key Words ◽  
Mole Fraction ◽  
Composition Range ◽  
Hydrophobic Moiety ◽  
Enthalpic Interaction ◽  
Mixing Schemes ◽  
Small Increments ◽  
Partial Molar Enthalpies ◽  
Transition Of Mixing Scheme

Excess partial molar enthalpies, HAE, of methanol, ethanol, and 1- and 2-propanols in aqueous solutions were measured directly, accurately, and in small increments in mole fraction at 25 °C. From these data, the solute–solute enthalpic interactions, HAAE≡N(∂HAE/∂nA), were evaluated for each alcohol. These data indicate that three distinctively different mixing schemes, I, II, and III exist, as was the case for aqueous 2-butoxyethanol previously studied in our laboratory. The transition from mixing scheme I to II appears to take place gradually within a small composition range. As the hydrophobic moiety becomes smaller from 2-butoxyethanol to methanol, the locus of the transition moves to a higher value in mole fraction of the alcohol. At the same time, the range of transition becomes wider and the solute–solute enthalpic interaction weaker. Key words: excess partial molar enthalpies in aqueous solutions, methanol, ethanol, 1-propanol, 2-propanol, enthalpic interaction, transition of mixing scheme.

scholarly journals Cobalt electrodeposition onto polycrystalline gold from ammoniacal solutions

2013 ◽  
Vol 11 (8) ◽  
pp. 1381-1392 ◽  
Author(s):  
Luis Mendoza-Huizar ◽  
Clara Rios-Reyes
Keyword(s):  
Free Energy ◽  
Aqueous Solutions ◽  
Transfer Coefficient ◽  
Gibbs Free Energy ◽  
Nucleation Rate ◽  
Nucleation Sites ◽  
Linear Voltammetry ◽  
Polycrystalline Gold ◽  
Cobalt Electrodeposition ◽  
Saturation Number

AbstractIn the present work, the cobalt electrodeposition onto polycrystalline gold electrodes from aqueous solutions containing 0.01M CoSO4 + 1 M (NH4)2SO4 at pH=7 was analyzed. Linear voltammetry results suggested a change in the kinetic of the cobalt electrodeposition. In all cases, the nucleation rate (A), the number of active nucleation sites (N 0) and the saturation number of nuclei (N s ) values were potential dependent. The calculated Gibbs free energy (ΔG) for this system was 1.88×10−20 J nuclei−1 and the transfer coefficient for the Hydrogen Electroreduction Reaction (HER) was 0.47.

Excess partial molar enthalpies in the water-rich region of the isobutyric acid – water system

1991 ◽  
Vol 69 (7) ◽  
pp. 1065-1069 ◽  
Author(s):  
William W. Y. Siu ◽  
Terrance Y. H. Wong ◽  
Lisa C. F. Chao ◽  
Yoshikata Koga
Keyword(s):  
Phase Separation ◽  
Water System ◽  
Isobutyric Acid ◽  
Acid Water ◽  
Rich Region ◽  
Two Phase ◽  
Fourth Derivative ◽  
Mixing Schemes ◽  
Partial Molar Enthalpies ◽  
Structure Enhancement

The excess partial molar enthalpies of isobutyric acid (IBA), HmE(IBA), and those of H2O, HmE(H2O), were measured in aqueous solutions of IBA. The temperature dependence of HmE(IBA) at the infinite dilution suggested that the structure enhancement of the solvent H2O by IBA is weaker than those by tert-butanol (TBA) or 2-butoxyethanol (BE). The concentration dependence of HmE(IBA), and that of the enthalpic IBA–IBA interaction, N{∂HmE(IBA)/∂nB}, shows that there are two distinct mixing schemes bounded at about xB = 0.03, before reaching the two phase separation. Namely, the IBA–IBA interaction is repulsive below this boundary, while above this boundary it becomes attractive leading eventually to phase separation at a higher concentration. The transition between the two schemes is associated with a peak(negative) anomally in the fourth derivative of the free energy, N2 {∂2HmE(IBA)/∂nB2}.Key words: excess partial molar enthalpies, isobutyric acid – water, transition in mixing scheme.

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