Showing papers on "Standard molar entropy published in 1980"

Adsorption of proteins at the polar oil—water interface

Abstract: Adsorption isotherms of BSA and gelatin at the polar peanut oil—water interface have been studied as a function of biopolymer concentration, ionic strength of the medium, pH, and temperature For BSA, the maximum amount adsorbed at saturation (Γ p m ) is found to be affected appreciably by the presence of various neutral salts such as KSCN, Na 2 SO 4 , LiCl, and CaCl 2 Ionic strength has little effect on the isotherms near the isoelectric pH 50 Γ p m for BSA is affected by the change in pH, and the extent of adsorption decreases with temperature increase However, the isotherm for gelatin is insensitive to change in pH and temperature After initial saturation, Γ p for gelatin further increases sharply without limit even when the equilibrium protein concentration has been brought to 16% The values of the standard free energy change for adsorption have been calculated on the basis of the Gibbs equation The standard entropy and enthalpy changes calculated therefrom are positive

Experimental heat capacities of LaNi5, α‐LaNi5H0.36, and β‐LaNi5H6.39 from 5 to 300 °K. Thermodynamic properties of the LaNi5–H2 system

Abstract: The heat capacities of LaNi5, α‐LaNi5H0.36, and β‐LaNi5H6.39 were measured from 5 to 300 °K, and in the case of LaNi5 also from 300 to 350 °K. Various special techniques and unusual circumstances involved in the measurements and calculations are described. A slight enhancement of the heat capacity of β‐LaNi5H6.39 was observed in the temperature range 120 to 160 °K. The standard entropies of LaNi5, α‐LaNi5H0.36, and β‐LaNi5H6.39 at 298.15 °K were found to be 209.9±0.5, 214.1 ±0.5, and 271.7±0.7 J °K−1 mole−1, respectively. These results together with other thermochemical data were used to calculate the entropy and enthalpy of formation of β‐LaNi5H6.39 at 298.15 °K. The partial molar entropy of hydrogen in β‐LaNi5H6.39 was derived from our results and used to estimate the configurational entropy at 298.15 °K.

Thermodynamic study on mixed monolayers of butyl eicosanedioate and tetradecanoic acid.

Abstract: In order to clarify the behavior of mixed monolayers of butyl eicosanedioate and tetradecanoic acid, the surface pressure was measured as a function of mean area at various compositions and temperatures. Four types of phase transition were observed. By use of the thermodynamic treatment previously developed, the apparent molar entropy and energy changes associated with the phase transition were evaluated. It was concluded on thermodynamic considerations that the butyl eicosanedioate and tetradecanoic acid monolayers are immiscible in condensed states and their phase diagram has a two-dimensional eutectic point.

Adsorption of 4 He on neon-coated exfoliated graphite

Abstract: Adsorption isotherms of 4He on Grafoil coated with a monolayer of neon were made for the temperature range of 2–10 K and in the pressure range of 0.10–15.00 Torr, using a standard volumetric method. From these isotherms the isosteric heats of adsorption were calculated as a function of coverage. The binding energy of 4He on Ne was obtained from the isosteric heat for V → 0, yielding a value of 39.4 K. The differential molar entropy and the internal molar energy were calculated as a function of coverage. A comparison of monolayer coverage obtained by analyzing different procedures is presented. Whenever possible the results are compared with theoretical evaluations and previous experimental data.

New approach for the elucidation of the ipso- and .ALPHA.-13C substituent induced chemical shifts by the linear combination of the empirical parameters.

Abstract: ^ C substituent chemical shift (S.C.S.) of the aromatic ipso- and aliphatic α- positions can be expressed by the linear combination of the substituent constants σi, σπ and the standard entropy difference ΔS°. [numerical formula] ΔS°+ and ΔS°- denote the standard entropy difference of the electron donating and electron attracting substituent groups.

Studies on 13C magnetic resonance spectroscopy. XVI. On the introduction of the entropy term .DELTA.S.DEG. for the elucidation of Ipso- and .ALPHA.-13C substituent-induced chemical shifts by an empirical approach.

Abstract: ^ C Substituent-induced chemical shifts (SCS) at the ipso and α positions of monosubstituted benzenes or methanes can be expressed by a linear combination of three kinds of empirical parameters, σi, σπ, and ΔS°. ΔS° represents the difference of the entropy (due to the substituent) between the standard entropy S°of the substituted compound and that of the parent one. The following results were obtained. SCSipso=63.9·σi-3.9·σπ+0.6ΔS°+-0.4·ΔS°-+3.8 (r=0.927, SD=4.9 ppm, n=13) SCSα=162.1·σi-10.1·σπ+1.2·ΔS°+-0.3·ΔS°-+2.3 (r=0.976, SD=4.9ppm, n=13) where + and - subscripts of ΔS° indicate electron-donating and -attracting groups, respectively. This treatment is also applicable for elucidation of the 13C SCS of analogous positions of many substituted aromatics and heteroaromatics, including ortho-disubstituted benzenes, and provides a reasonable and explicit chemical basis for the origin of the 13C SCSipso and SCSα. The same treatment also provides an explicit chemical basis for Mulliken's electronegativity scale and the steric substituent constant, Es.

Molare Entropien von Salzschmelzen zwischen 600 K und 3000 K

Abstract: Die molare Entropie geschmolzener Salze einer Gruppe des Periodensystems mit einem gemeinsamen Anion hangt in sehr guter Naherung linear vom Kationenradius ab. Die Extrapolation der molaren Entropie fur gegen Null gehenden Kationenradius (rk 0) liefert den Anteil der molaren Entropie fur dieses gemeinsame Anion, aus dem sich mit experimentellen Daten die zugehorigen Kationenanteile der Entropie und weitere Anionenanteile berechnen lassen. Mit diesen Ionenanteilen last sich die molare Entropie einer grosen Anzahl von geschmolzenen Salzen in einem Temperaturbereich von 600 K bis 3000 K je nach dem Schmelz- und Siedepunkt bzw. der Zersetzungstemperatur mit einer Abweichung von etwa 2,5% abschatzen. The molar entropy of molten salts which consists of cations of one group of the periodic table and of a common anion, depends linearly on the cation radius in very good approach. The extrapolation of the molar entropy for rk 0 (rk = cation radius) gives the anion contribution of molar entropy from which together with experimental data the corresponding cation contributions of entropy and further anion contributions can be evaluated. By means of these ion contributions of entropy the molar entropies of a great number of molten salts can be estimated within a mean deviation of about 2.5% in temperature ranges between 600 K and 3000 K according to the melting and boiling points and the decomposition temperature of the melt.