Showing papers on "Standard molar entropy published in 1975"
TL;DR: The apparent first ionization constant of carbonic acid has been determined by conductivity measurements and found to vary from 4.32×10−7 at 25°C to 1.6 × 10−8 at 250°C.
Abstract: The apparent first ionization constant of carbonic acid has been determined by conductivity measurements and found to vary from 4.32×10−7 at 25°C to 1.6×10−8 at 250°C. The pressure effect to 2000 bar has been measured, and the ratio Kp/K1 is 7.3 at 25°C and 19 at 250°C. The standard partial molar volume change for the ionization at 1 bar,
$$\Delta \bar V_1^0$$
, increases from −27.6 cm3-mole−1 at 25°C to −88 cm3-mole−1 at 250°C. The volume changes are smaller at higher pressures. A linear correlation between
$$\Delta \bar V_1^0$$
and the partial molar compressibility for the ionization reaction has been noted. A similar correlation exists between the partial molar entropy and volume changes for the reaction.
100 citations
TL;DR: The characterization of recently synthesized (Pro‐Pro‐Gly)n, n = 7, 8 is described, along with melting profile studies of its association equilibrium, and thermal quenching studies of the kinetics ofIts association reaction.
Abstract: The characterization of recently synthesized (Pro-Pro-Gly)n, n = 7, 8 is described, along with melting profile studies of its association equilibrium, and thermal quenching studies of the kinetics of its association reaction. The order of the kinetic reaction is about 3, implying that three peptide chains are involved in the activated state of the rate-limiting step. The reaction rate was found to exhibit a negative temperature coefficient. With the (Pro-Pro-Gly)7 peptide, the concentration dependence of the (Pro-Pro-Gly)n association equilibrium was observed for the first time.
Detailed thermodynamic analysis for these n = 7, 8 data, together with literature data for n = 10, 15, 20 were carried out for both the simple “all-or-none” binding model and for a series of complex equilibrium models. For the latter, all of the (Pro-Pro-Gly)n data (in 10% acetic acid) are fit best with a maximally cooperative near-neighbor model with a standard enthalpy change ΔH = −650 cal/mole of residues, and a standard entropy change ΔS = −14.63 −10/n cal/deg-mole of residues, wherein the −10 eu represents an end-effect contribution to the binding free energy.
With regard to optical rotatory properties and thermodynamic parameters, the data for the new n = 7, 8 peptides match rather well with the literature data for the n = 10, 15, and 20 peptides.
The enthalpic stabilization per residue of the triple-helical form of (Pro-Pro-Gly)n was nearly an order of magnitude smaller than the enthalpic stabilization per additional proline obtained from direct calorimetric measurements on native collagens of different (and much lower) proline contents by Privalov and Tiktopulo. [Biopolymers (1970) 9, 127–139.] Possible explanations for this phenomenon are discussed.
27 citations
TL;DR: In this paper, the relative molar entropy of a solution is proportional to the molar enthalpy of solution and a variation of rotational entropy during solution, and the variation of the rotation is dependent on the geometrical structure of solute molecules.
Abstract: Some relationships between enthalpy and entropy changes on selectivities of stationary phases in GLC are derived. It is shown that the relative molar entropy of solution is proportional to the relative molar enthalpy of solution and a variation of rotational entropy during solution. Application of these relationships to systems with simple and complex solute molecules (alkylbenzenes, isoparaffins and some spherical molecules) is discussed. The variation of the rotational entropy depends on the geometrical structure of solute molecules; therefore such a parameter may be used for identification.
21 citations
TL;DR: In this paper, the growth rate vs. temperature relation of Na 2 O · 3SiO 2 has been determined over the temperature range between 600°C and 800°C, with the maximum growth rate (3.3 x 10 -6 cm sec -1 ) observed at 735 °C.
20 citations
TL;DR: The heat capacity of tungsten carbide has been measured by adiabatic and differential scanning calorimetry from 14 to 348 K and by differential scanning from 226 to 995 K, respectively as mentioned in this paper.
17 citations
TL;DR: In this article, the rate of change of the standard chemical potential with solvent composition was calculated from precise vapor-pressure measurements for urea at three temperatures and for thiourea at 298.15°K in water-tetrahydrofuran (THF) mixtures.
Abstract: The rate of change of the standard chemical potential with solvent composition,
$$\partial \bar G_0 /\partial Z$$
, has been calculated from precise vapor-pressure measurements for urea at three temperatures and for thiourea at 298.15°K in water-tetrahydrofuran (THF) mixtures. From these results the standard free energy of transfer ΔG
t
o
of the solutes from water to various water-THF mixtures has been obtained together with the standard molar entropy ΔS
t
o
and the standard molar enthalpy ΔH
t
o
of transfer at 298.15°K in the case of urea. The quantity ΔG
t
o
for urea is negative in the water-rich region and positive for mole fractions THF>0.2. There is a nearly complete compensation between ΔH
t
o
andTΔS
t
o
at 298.15°K up to mole fraction THF=0.5. These phenomena can be partly related to the structure in H2O-THF mixtures.
11 citations
TL;DR: Results show that insolubilization has no effect on the standard enthalpy change but lowers the value for the standard entropy change, and this effect appears to be independent of the concentration of the gel matrix to which the cytochrome c is bound, but dependent on the ionic strength of the surrounding solution.
Abstract: A method is described for computer analysis of simple spectrophotometric changes in particulate systems, and this has been applied to the bleaching of the 695 nm band of insoluble ferricytochrome c by temperature. The results show that insolubilization has no effect on the standard enthalpy change but lowers the value for the standard entropy change. This effect appears to be independent of the concentration of the gel matrix to which the cytochrome c is bound, but dependent on the ionic strength of the surrounding solution.
9 citations
TL;DR: It has been shown that sodium dodecyl sulfate (SDS) is capable of forming stable complexes with amylose and that fractionation of short-chain amyloses can be effected by SDS-gel electrophoresis.
Abstract: It has been shown that sodium dodecyl sulfate (SDS) is capable of forming stable complexes with amylose and that fractionation of short-chain amyloses can be effected by SDS-gel electrophoresis. Using a well-defined smylose fraction (molecular weight 4,000), the thermodynamic parameters pertaining to SDS-amylose interaction have been evaluated by means of frontal gel chromatography. The results are as follows: association constant (K)=5.0 times 10-3-M-minus 1 at 25 degrees (pH 9.4); standard free energy change (delta G degrees)=-5.1 kcal/mole; standard enthalpy change (delta H degrees)=-5.8 kcal/mole; standard entropy change (delta Sdegrees)=-2.3(e.u.) and the maximum number of binding sites for SDS (n)=1. In the presence of 0.5--1 percent SDS, amylose migrates toward the anode upon gel electrophoresis, giving a compact band. High resolution of amylose fractions (released by treatment of amylopectin with debranching enzyme) has been attained using pore-size gradient gel electrophoresis.
8 citations
6 citations
TL;DR: In this article, the standard enthalpy of formation, ΔH f 0 (CsNO 3, c, 298.15 K) was calculated to be −(120.88 ± 0.12) kcal th mol −1.
5 citations
TL;DR: In this article, the authors measured thermodynamic stability and entropy changes in six solubilized solutions containing lauric acid, palmitic acid and myristic acid at 35, 45, 55°C.
Abstract: Thermodynamic stability and entropy changes were measured in six solubilized solutions containing lauric acid, palmitic acid, myristic acid, stearic acid, behanic acid and their corresponding sodium salts dissolved in water at 35, 45, 55°C, using the partial molar volume method. It was inferred that clusters or loose combinations of molecules were formed during solubilization (supporting von BUZOOH'S view). Thermodynamic stability and entropy changes decreased with the increase of carbon atoms or temperatures, making the solubilized solutions heterogeneous and thermodynamically unstable, contrary to the views of McBain who called these solutions thermodynamically stable.
TL;DR: In this paper, it was shown that in mixtures containing K components, K states of maximal stability can be defined, each of them corresponding to the case when one component disappears from the mixtures.
Abstract: It is shown that in mixtures containingK componentsK states of maximal stability can be defined, each of them corresponding to the case, when one component disappears from the mixtures. On the ground of the thermostatic theory of stability it can be stated that these states like states of maximal stability in general, can be approximated arbitrarily, but cannot be reached, so that they have properties analogous with the state of absolute zero temperature.