Standard molar entropy

About: Standard molar entropy is a research topic. Over the lifetime, 1586 publications have been published within this topic receiving 29886 citations.

Pore morphological identification of hydrotalcite from nitrogen adsorption

Abstract: The characteristic energy of nitrogen adsorption in a meso-porous hydrotalcite at 77 K demonstrates the fractality over wider range of pore sizes including meso and macro-pores. More irregular, wider pore-size distribution exhibits higher adsorption potential than that with more regular, narrower pore-size distribution. The changes in differential molar entropy during the adsorption indicate that an irreversibly chaotic process associated with transition from a disordered gaseous state to a more ordered adsorbed state occurs. The differential entropy of adsorption decreases at increasing fractality. The increase in ‘pure’ isosteric enthalpy of adsorption with increasing fractality indicates that the energy is closely related to the pore-size distribution.

Gel electrophoresis of amylose in the presence of sodium dodecyl sulfate.

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.

Thermodynamic properties of triphenylantimony dibenzoate

Abstract: The temperature dependence of the heat capacity of triphenylantimony dibenzoate Ph3Sb(OC(O)Ph)2 is studied in the range of 6–480 K by means of precision adiabatic vacuum calorimetry and differential scanning calorimetry. The melting of the compound is observed in this temperature range, and its standard thermodynamic characteristics are identified and analyzed. Ph3Sb(OC(O)Ph)2 is obtained in a metastable amorphous state in a calorimeter. The standard thermodynamic functions of Ph3Sb(OC(O)Ph)2 in the crystalline and liquid states are calculated from the obtained experimental data: C ° (T), H°(T)–H°(0), S°(T), and G°(T)–H°(0) for the region from T → 0 to 480 K. The standard entropy of formation of the compound in the crystalline state at T = 298.15 K is determined. Multifractal processing of the low-temperature (T < 50 K) heat capacity of the compound is performed. It is concluded that the structure of the compound has a planar chain topology.

Solubility and dissolution thermodynamics of phthalic anhydride in organic solvents at 283–313 K

Abstract: The solubility of phthalic anhydride was measured at 283–313 K under atmospheric pressure in ethyl acetate, n-propyl acetate, methyl acetate, acetone, 1,4-dioxane, n-hexane, n-butyl acetate, cyclohexane, and dichloromethane. The solubility of phthalic anhydride in all solvents increased with the increasing temperature. The Van’t Hoff equation, modified Apelblat equation, λh equation, and Wilson model were used to correlate the experimental solubility data. The standard dissolution enthalpy, the standard entropy, and the standard Gibbs energy were evaluated based on the Van’t Hoff analysis. The experimental data and model parameters would be useful for optimizing of the separation processes involving phthalic anhydride.