Enthalpy increment function

Enthalpy increment measurements to derive the high-temperature heat capacity have been reported for all lanthanide trifluorides except PmF3, as summarised in table 7. The results of the various authors are compared using the reduced enthalpy increment function ... 

The heat capacity of thiazole was determined by adiabatic calorimetry from 5 to 340 K by Goursot and Westrum (295,296). A glass-type transition occurs between 145 and 175°K. Melting occurs at 239.53°K (-33-62°C) with an enthalpy increment of 2292 cal mole and an entropy increment of 9-57 cal mole °K . Table 1-44 summarizes the variations as a function of temperature of the most important thermodynamic properties of thiazole molar heat capacity Cp, standard entropy S°, and Gibbs function - G°-H" )IT. 

Figure 14 shows a plot of this function for LaF3. It can be seen that the data for the enthalpy increment by Spedding and Henderson (1971) and Lyon et al. (1978) are in good... 

The JANAF Thermochemical Tables consist of thermal functions and formation functions, both of which are temperature dependent. The thermal functions consist of heat capacity, enthalpy increments, entropy, and Gibbs en-... 

The layout of the tables and the functions quoted correspond to conventions which are also used in standard works such as the JANAF Tables and the Tables of the U.S. Bureau of Mines. The following thermochemical functions are tabulated heat capacity Cp, entropy S, Gibbs energy function —Gef = - [C-//(298.15)1 / 7] enthalpy H, enthalpy increment //-//(298.15), Gibbs energy G = H-TS, and the formation quantities AH(,AG and logA f. The formation reactions refer to the reference states of the elements, which are given in a separate table. 

Subsequently, Huntelaar et al. [95HUN/COR] measured the heat capacity and related thermochemical properties of SrZrSi207(s). The heat capacity was measured between 10 and 320 K using adiabatic calorimetry whereas enthalpy increments relative to 298.15 K were determined between 400 and 850 K using drop calorimetry. After correction for a zirconia impurity and estimation of the heat capacity below 13 K using the function A.T (where A is 0.000251 J-moP ), the heat capacity and entropy at... 

Since (Hj-H s) values (Meyers and Graves, 1977a Krasnov and Danoliva, 1969) are only reported for a limited set of temperatures, the enthalpy increments reported by Meyers and Graves for the 298-2000 K range have been fit to a polynomial function of temperature. Interpolated results for SCF3 and YF3... 

Ideal gas values for the heat capacity, enthalpy increment, and entropy can be computed from the partition function Q. 

C2H6O), methanol (CH4O) and acetone (CsHeO) at a constant content of water (0.5 mol.fr.) (Wormald and Vine, 2000 Wormald and Yerlett, 2000, 2002). The enthalpy increments (AH), measured with a cormter-current water-cooled flow calorimeter, were plotted as a function of pressure and represented as a set of isothermal p-AH curves. If these curves cross a two-phase region, they have two breaks at the dew and bubble point pressures, and the straight lines between them. In this way the values of the molar enthalpy of the saturated vapor and the molar enthalpy of the saturated liquid were obtained, as well as the molar enthalpy of flash vaporization of the mixtures. 

Fig. 71 Polystyrene the changes in resistance to deformation (a), energetic state (AH) and IR spectral characteristics as a function of pre-straining on compression at 20°C [15] (1) the stress-strain curve for annealed samples (2) ditto for quenched samples (3) enthalpy increment AH (DSC) (4) the extinction coefficient i602 of the IR band of deformation vibrations of the benzene rings at 1,602cm" as a measure of universal IMI (5) increment in mechanical loss (internal friction) A5ip (6) the ratio of optical densities of the IR bands at 560 and 542 cm" as a criteria of changes in the conformational composition...

Values rounded off from Chappell and Cockshutt, Nat. Res. Counc. Can. Rep. NRC LR 759 (NRC No. 14300), 1974. This source tabulates values of seven thermodynamic functions at 1-K increments from 200 to 2200 K in SI units and at other increments for two other unit systems. An earlier report (NRC LR 381, 1963) gives a more detailed description of an earlier fitting from 200 to 1400 K. In the above table h = specific enthalpy, kj/kg, and = logio for m isentrope. In terms of... 

The liquid enthalpy of formation difference between 1-hexyl and 1-heptyl hydroperoxides is almost twice that of a normal enthalpy of formation methylene increment of about 25 kJmol . But which of these two, if either, is correct For hydrocarbon snb-stituents bonded to electronegative functional groups, the secondary isomers are more stable than the n-isomer. Accordingly, either the 1- or 4-heptyl hydroperoxide, or both, have an inaccurate enthalpy of formation because the primary isomer is reported to have the more negative enthalpy of formation. All of the enthalpies of formation for the Cg and C7 hydroperoxides cited in Reference 2 come from a single source. There is a reported value for the gas phase enthalpy of formation of fert-butyl hydroperoxide that is 11 kJ mol less negative than the value in Reference 2. 

The linear correlation of enthalpies of formation with the number of carbon atoms is a useful and well-known feature of homologous series of functionalized organic compounds. The slope of the regression line for the gaseous n-alkanes (CH3—(CH2)j —H), —20.6 kJmol-, and the similar values of the slopes for other CH3—(CHi) —Z series is often called the universal methylene increment . In the liquid phase, the increment for the n-alkanes is —25.6 0.1 klmoD. The most accurate determination of the increment... 

The AG of the reaction is then calculated in one of two ways (1) the appropriate addition and substraction of AGf for reactants and products, or (2) the calculation of Gibbs energy functions for reactants and products from enthalpy and entropy increments... 

Abstract Enantioselection in a stoichiometric or catalytic reaction is governed by small increments of free enthalpy of activation, and such transformations are thus in principle suited to assessing dendrimer effects which result from the immobilization of molecular catalysts. Chiral dendrimer catalysts, which possess a high level of structural regularity, molecular monodispersity and well-defined catalytic sites, have been generated either by attachment of achiral complexes to chiral dendrimer structures or by immobilization of chiral catalysts to non-chiral dendrimers. As monodispersed macromolecular supports they provide ideal model systems for less regularly structured but commercially more viable supports such as hyperbranched polymers, and have been successfully employed in continuous-flow membrane reactors. The combination of an efficient control over the environment of the active sites of multi-functional catalysts and their immobilization on an insoluble macromolecular support has resulted in the synthesis of catalytic dendronized polymers. In these, the catalysts are attached in a well-defined way to the dendritic sections, thus ensuring a well-defined microenvironment which is similar to that of the soluble molecular species or at least closely related to the dendrimer catalysts themselves. 

Fig. 4. Temperature dependence of the specific enthalpy of denaturation of myoglobin and ribonuclease A (per mole of amino acid residues) in solutions with pH and buffer providing maximal stability of these proteins and compensation of heat effects of ionization (see Privalov and Khechinashvili, 1974). The broken extension of the solid lines represents a region that is less certain due to uncertainty in the A°CP function (see Fig. 2). The dot-and-dash lines represent the functions calculated with the assumption that the denaturation heat capacity increment is temperature independent.

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