Showing papers on "Standard molar entropy published in 1977"

Interpretation of the thermodynamic, spectroscopic and dielectric properties of solutions of ethanol in cyclohexane in terms of association

Abstract: A model is proposed to explain the thermodynamic, spectroscopic and dielectric properties of dilute solutions of ethanol in cyclohexane in terms of association into both open-chain and cyclic hydrogen bonded groups, with allowance for a Van der Waals interaction term. It proves necessary to specify: two standard enthalpies for formation of the H-bonds, h2=–21.2 kJ mol–1 for the dimer and h=–23.5 kJ mol–1 for all larger groups; three standard entropies of stepwise formation (for the dimer, trimer and all higher open-chain forms); and a standard entropy of formation from open-chain to cyclic groups, which are assumed to be present to a significant extent only for groups of more than four molecules. This model gives a quantitative reproduction of the activity coefficients, enthalpies of mixing and i.r. spectroscopic behaviour, and accounts for the initial decrease in the apparent dipole moment.

Die Thermodynamik der Verdampfung der Kupfer(I)‐Halogenide

Abstract: Die Verdampfungsgleichgewichte der Kupfer(I)-halogenide wurden mit einer statischen Methode gemessen. Der Dampf besteht uberwiegend aus Trimeren. Folgende Verdampfungsenthalpien und -entropien bei 1 100 K wurden bestimmt (in kcal/Mol bzw. Clausius): CuCl: 42,7; 23,8; Cu2Cl2: 43,1; 19,7; Cu3Cl3: 18,4; 10,0; Cu4Cl4: 15,5; 5,9; Cu3Br3: 19,6; 11,3; Cu4Br4: 24,0; 7,8; Cu3J3: 25,1; 14,8. Unter Hinzuziehung der Beobachtungen beim chemischen Transport von Cu mit Jod wurde die Standardentropie bei 298 K fur Cu3J3,g erhalten zu 130 cl und die Bildungsenthalpie zu 20 kcal/Mol. Thermodynamics of the Vaporization of Copper(I) Halides The equilibria of the vaporization of copper(I) halides were measured by means of a static method. The predominant species in the vapour are the trimeric ones. The enthalpies and entropies of vaporization (kcal/mol and e. u./mol) at 1 100 K were determined to be 42.7 and 23.8 fur CuCl, 43.1 and 10.7 for Cu2Cl2, 18.4 and 10.0 fur Cu3Cl3, 15.5 and 5.9 for Cu4Cl4, 10.6 and 11.3 for Cu3Br3, 24.0 and 7.8 for Cu4Br4, 25.1 and 14.8 for Cu3I3, respectively. Taking into account the results of chemical transport experiments concerning the transport of copper by means of iodine, the standard entropy at 298 K of Cu3I3(gas) was found to be 130 e. u./mol and the fusion enthalpy at 298 K was determined to be 20 kcal/mol.

Zersetzungsgleichgewicht und Bildungsenthalpie von Te6O11Cl2

Abstract: Das Zersetzungsgleichgewicht des Te6O11Cl2 wurde im Membrannullmanometer gemessen. Neben festem TeO2 und Te6O11Cl2 liegen in der Gasphase TeOCl2, TeCl4, TeCl2 und Cl2 vor. Aus dem Zersetzungsgleichgewicht wurde die Bildungsenthalpie zu −472,5 ± 10 kcal/Mol und die Standardentropie zu 126 ± 10 cl abgeleitet. Die Losungswarme des Te6O11Cl2 wurde durch Losen in KOH ermittelt. Es folgt die Bildungsenthalpie ΔH°(Te6O11Cl2, 298) = −473,4 ± 8 kcal/Mol. The Decomposition Equilibrium and the Enthalpy of Formation of Te6O11Cl2 The decomposition equilibrium of Te6O11Cl2 has been investigated in a membrane manometer. TeOCl2, TeCl4, TeCl2 and Cl2 exist in the gas phase over solid TeO2 and Te6O11Cl2. From the decomposition equilibrium the enthalpy of formation −472.5 ± 10 kcal/mol and the standard entropy 126 ± 10 cl were derived. The enthalpy of solution in KOH gives the enthalpy of formation ΔH°(Te6O11Cl2, 298) = −473,4 ± 8 kcal/mol.

Thermodynamics of the binding of flavin adenine dinucleotide to D-amino acid oxidase.

Abstract: The enthalpy of binding, ΔH b , of flavin adenine dinucleotide to the apoenzyme of D-amino acid oxidase was determined by flow calorimetry at pH 8.5 to be +3.8, −4.1 and −11.0 kcal mol −1 at 10 °, 25 ° and 38 °, respectively. These values correspond to a heat capacity change, ΔCp, of −530 cal K −1 mol −1 . From the binding constant reported by Dixon and Kleppe (1965a) and the above enthalpies, the standard free energy and standard entropy of binding are evaluated. These thermodynamic data are interpreted in terms of hydrophobic and vibrational contributions ( Sturtevant, 1977 ). The product of the assay reaction ( Fonda and Anderson, 1967 ), benzoylformic acid, is a non-competitive inhibitor of the enzyme with a value for k i of 1.4 × 10 −4 M at 25 °.