Showing papers on "Standard molar entropy published in 1989"
TL;DR: The values of the critical micelle concentration, CMC, were determined from the intersections of two straight line portions of the plots of the relationship between adiabatic compressibility of the solutions and surfactant concentration.
89 citations
TL;DR: In this paper, it was shown that the adsorption standard entropy shows a compensation effect with adsorship enthalpy, which is more or less Langmuirian.
Abstract: Joint i.r. and microcalorimetric work has shown that two types of CO adsorb on pure anatase: one (species A) absorbing at 2184–2188 cm–1, has an adsorption heat of ca. 52 kJ mol–1, the other (species B), absorbing at 2203–2208 cm–1, has an adsorption heat of 69 kJ mol–1. When sulphates are present at the surface, left from the process of preparation, species B is suppressed, and species A absorbs at 2190–2196 cm–1, with an adsorption heat of 59 kJ mol–1. The CO species have been characterized also through their molar extinction coefficient and entropy of adsorption at vanishing coverage. By comparison with other data on similar systems it can be shown that, when adsorbing CO on non-d cations, these physical properties are related to one another in simple ways. In particular, it was found that the adsorption standard entropy shows a compensation effect with adsorption enthalpy. The adsorption of species B is more or less Langmuirian, whereas the adsorption on sites A is non-ideal, as shown by several features (i.e. non-Langmuirian isotherms, shifts of the CO stretching frequency, changes on differential heats), probably because inductive effects are readily transmitted through the semiconductive TiO2 solid.
43 citations
TL;DR: In this article, the activity of nickel in solid Cu-Ni alloys has been measured at 1000 K using a solid state galvanic cell incorporating calcia stabilised zirconia as the solid electrolyte.
Abstract: The activity of nickel in solid Cu–Ni alloys has been measured at 1000 K using a solid state galvanic cell incorporating calcia stabilised zirconia as the solid electrolyte. The activity of nickel shows positive deviation from Raoult's law over the entire range of concentration. Partial molar entropy of nickel in solid Cu–Ni alloys has been measured directly using a newly developed twin solid state thermocell apparatus. A consistent set of thermodynamic data for the Cu–Ni system has been 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 and diffuse neutron scattering studies reported in the literature.MST/968
30 citations
TL;DR: The equilibrium solid solubility of antimony in silicon was determined in the range 850°-1300°C by carrier density measurements on polysilicon films doped by ion implantation as mentioned in this paper.
Abstract: The equilibrium solid solubility of antimony in silicon was determined in the range 850°–1300°C by carrier density measurements on polysilicon films doped by ion implantation. Up to 1150°C this property follows very tightly the exponential dependence with and . The values at higher temperatures show a smaller increase, the figures at 1200°, 1250°, and 1300°C being , respectively. The attainment of the two‐phase equilibrium was confirmed by carrier profile measurements on isothermally annealed single‐crystal specimens doped in a wide range of concentrations, as well as by TEM examinations which detected a high density of particles having the hexagonal structure of antimony. It is shown that the new solubility values, unlike the previous ones, fully comply with the conditions for phase equilibrium. According to this treatment, the values of 0.58 eV and of are deduced for the partial molar enthalpy and, respectively, for the excess partial molar entropy of the dopant in silicon relative to the standard liquid state of antimony.
29 citations
TL;DR: In this paper, the solubilities and solubility products of 14 lanthanon trifluorides (LnF3· 0.5H2O) have been determined using conductometric, potentiometric and radiometric techniques.
Abstract: Solubilities and solubility products of 14 lanthanon trifluorides (LnF3· 0.5H2O) have been determined using conductometric, potentiometric and radiometric techniques. The solubilities and the averages of selected pKsp values from literature and from our own work, that do not differ by more than one unit, show three maxima when plotted against the atomic number of lanthanons. Standard enthalpy change measured from the temperature-dependence plots of Ksp and the free-energy change calculated from Ksp of the trifluorides fall within the range 30–60 kJ mol–1 and 78–103 kJ mol–1, respectively, in most cases. Standard entropy change calculated from the enthalpy and free energy changes ranges from –47 to –294 J K–1 mol–1. The stability constants determined for the monofluoride complexes fall within the range of reported values, but those for the difluoride complexes are much higher than the fewer values that are found in literature. Lanthanon trifluorides were found to be least soluble in water at pH 3–4.
27 citations
TL;DR: In this article, light scattering was used to establish the dependence of the critical micelle temperature, CMT, on concentration for solutions of three polystyrene-block-poly(ethylene/propylene) copolymers in decane.
Abstract: Light scattering was used to establish the dependence of the critical micelle temperature, CMT, on concentration for solutions of three polystyrene-block-poly(ethylene/propylene) copolymers in decane. Electron microscopy studies of particles isolated from the solutions showed that the micelles had narrow size distributions and micellization could be treated thermodynamically as a closed association. The light scattering results were used to calculate the standard Gibbs energies of micellization, ΔGφ, and the standard enthalpy, ΔHφ, and entropy contributions, —TΔSφ. The values of ΔHφ were large and negative, and markedly dependent on the molecular weight of the polystyrene block. The values of ΔGφ for the three samples were on the other hand very similar to each other. The standard entropy contributions were unfavourable to micelle formation.
26 citations
TL;DR: In this paper, the enthalpy change associated with the γ-β (orthorhombic to hexagonal) crystal-line transition for a specimen of barium carbonate standard (NBS-SRM 760) which is sold for temperature calibration of differential thermal analyzers was studied.
8 citations
TL;DR: In this article, the heat capacities of the cluster compounds [Ag6M4P12]Ge6 (M=Ge, Sn) have been measured in the temperature range from 2 K to 310 K. Thermal decomposition into the elements was carried out under Knudsen conditions on a thermobalance combined with a mass spectrometer.
Abstract: The heat capacities of thecluster compounds [Ag6M4P12]Ge6 (M=Ge, Sn) have been measured in the temperature range from 2 K to 310 K. Thermal decomposition into the elements was carried out under Knudsen conditions on a thermobalance combined with a mass spectrometer. The thermodynamic functions standard entropy, enthalpy, and the Debye temperatures were calculated from the heat capacity data. The vapour pressure functions derived from the Knudsen effusion data, served to calculate the third law heat of formation.
6 citations
TL;DR: A new equation for gas adsorption on microporous solids is proposed in this article, which is generated by the virial expansion of the spreading pressure of spreading pressure.
5 citations
TL;DR: The heat capacity of uranium at constant pressure was determined between 17.2 and 263.8 K in 100 steps and corrected to the heat capacity at constant volume C v. Taking into account the contribution C el by free electrons C v values could be calculated rendering a mean Debye temperature of 216.4 J K −1 mol −1 ; the c p value to 27.8 J K−1 mol−1.
4 citations
01 Jan 1989
TL;DR: In this article, 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.
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.
TL;DR: In this article, the solubility products and thermodynamic functions for the praseodymium and ytterbium fluoride-water systems have been measured using different analytical techniques for comparison among the measured values as well as with values reported in literature.
Abstract: The solubility products and thermodynamic functions for the praseodymium and ytterbium fluoride-water systems have been measured using different analytical techniques for comparison among the measured values as well as with values reported in literature. Although there is not much difference among our values obtained by potentiometric, conductometric and radiometric methods, the values for PrF3 disagree with at least two of the reported values. The effects of precipitant, aging of the precipitate and pH of the saturated solutions on the solubility product were studied and found to be significant. The standard enthalpy and free energy changes for the dissolution of both fluorides were found to be positive although the enthalpy for YbF3 is about twice as high as that for PrF3. The standard entropy change for PrF3 is negative, but that for YbF3 is positive. The overall stability constants for the mono- and difluoride complexes of both Pr and Yb have also been measured potentiometrically using a simplified approach.
TL;DR: In this paper, the electromotive force of liquid Hg-Na alloys was measured in detail below 15 at.% Na as functions of Na concentration and of temperature, and anomalous changes were observed in the concentration dependence curve of the excess partial molar entropy.
Abstract: The electromotive force (EMF) of liquid Hg-Na alloys was measured in detail below 15 at.% Na as functions of Na concentration and of temperature. On the basis of observed EMF values, thermodynamic functions of mixing were obtained at 398 K and 448 K. At 2-8 at.% Na anomalous changes were observed in the concentration dependence curve of the excess partial molar entropy, SPi,E (i=Na or Hg), and on that of the partial molar enthalpy of Na, HPNa,E. These anomalies indicate higher-order correlation effects arising from the characteristic changes in the concentration derivatives of n-body (n>or=2) correlation function galpha beta gamma (n). . . ( delta galpha beta gamma (n). . ./ delta ci)V,T,cj( not=i), which could be derived explicitly to be the function of the higher-order (n+1)-body correlation function galpha beta gamma (n) (n+1). . /sub /.
01 Dec 1989
TL;DR: In this paper, the authors used the theory of the adsorption potential to correlate the data of ethene, propene and 1-butene on a mesoporous Sc2O3 sample, at pressures up to 55 kPa.
Abstract: Adsorption data of ethene, propene and 1-butene on a mesoporous Sc2O3 sample are reported. Measurements were carried out in a volumetric apparatus and cover the range 213–373 K, at pressures up to 55 kPa. The theory of the adsorption potential has been applied to correlate adsorption data of olefins. Use has also been made of a multilayer adsorption approach, which takes into account the surface heterogeneity and makes it possible to calculate the parameters of an exponential distribution function of the sites according to their energies. Thermodynamic interfacial quantities (isosteric heat of adsorption and differential molar entropy) are determined from the adsorption data. A relationship between the isosteric heat of adsorption and the energetic parameter of the multilayer adsorption model is established and verified.
TL;DR: In this paper, the maximum possible lithium form of clinoptilolite (K1) with an ion exchange capacity of 2.3 mEq/g, corresponding to 85% Kl in nature, was prepared.
Abstract: The maximum possible lithium form of clinoptilolite (K1) with an ion-exchange capacity of 2.3 mEq/g, corresponding to 85% Kl in nature, was prepared. The isotherm of adsorption of water vapors on LiKl at 25°C in the region of maximally low equilibrium pressures (10−10 torr) was calculated by the adsorption-isostere method and permits determining the complete thermodynamic functions of the system. The adsorption isotherm is completely described by the two-term equation from the theory of volume filling of micropores (TVFM). The wavy-stepwise shape of the curve of the heat of adsorption permitted establishing the stoichiometric correlation between the adsorption values and concentration of Li+ in LiKl. The energy of the Li+-OH2 adsorption complex is 97 kJ/mole for a zero degree of filling. The integral average molar entropy of adsorption is 20 J/(mole·K) less than the entropy of a normal liquid. The state of the H2O molecules in LiKl is ice-like.