Gibbs function increment

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. 

This relationship identifies the surface energy as the increment of the Gibbs free energy per unit change in area at constant temperature, pressure, and number of moles. The path-dependent variable dWs in Eq. (2.60) has been replaced by a state variable, namely, the Gibbs free energy. The energy interpretation of y has been carried to the point where it has been identified with a specific thermodynamic function. As a result, many of the relationships that apply to G also apply to y ... 

Obviously, the evaluation of as a function of N depends decisively on the assumptions we make concerning the interactions between B neighbors or, more generally, those concerning K (n). If we let K = kn, which means that, each increment Ag in the Gibbs energy is the same if one B is added to B , independent of n, then... 

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... 

Fio. 6. The Gibbs energy difference of the native and denatured states of myoglobin and ribonuclease A calculated per mole of amino acid residues under the same conditions as indicated in Fig. 4. The dot-and-dash lines represent functions obtained in the assumption that the denaturation heat capacity increment is temperature independent. 

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. 

If the Gibbs energy or the equilibrium constant of a reaction is determined experimentally at a temperature >298.15 K (e.g. by emf measurements), then every measurement yields a value of A//r (298.15). However, a condition for this is that 5(7 ) and [//(T)-//(298.15)] are known. This precondition means that the increment of the Gibbs energy, i.e. G(r)-G (298.15) must be known. This reveals that the function G T) is sufficient for analysis by the Third Law method . Nevertheless, the changes in G T) and AG(T) are greater than is the case for Gef(T) and AGeffT), so that these latter are often preferred for a Third Law analysis. 

Figure 6. Computed vibration-rotation contributions to the Gibbs free energy and 4th-order polynomial curve fits for H20, HDO, and D20 as a function of temperature. AH computations were carried out using the AOSS-U Monte Carlo method in mass-weighted Jacobi coordinates. Three hundred Fourier coefficients were used per degree of freedom and 106 Monte Carlo samples were used for each calculation. Error bars at the 95% confidence level, as weU as all free energy fluctuations, are smaller than the width of the lines showing the curve fits. An increment of 10 was used over the temperature interval (1000-4000 K).

Discontinuities resulting from phase transitions in the reference elements can pose difficulties when interpolating from RHF-type tables, where enthalpies and free energies of formation are usually tabulated for temperature increments of 100°C. The problem can be circumvented to some extent by using the Gibbs energy function or Giauque function, —(G - H2 g)/T, which is listed in the fourth coltunn of these tables. The G and H symbols in this function refer to the absolute properties of the compound itself (not to the reference elements). Neither the G nor the H term is known, but the difference can be determined ( 7.5.4), and since 7/ 98 constant... 

Heat capacity measurements of sodium alkoxides (methoxide, ethoxide, n-propoxide and iso-propoxide) were carried out using DSC in die temperature range 240-550 K by Chandran and coworkers [219]. From the heat capacity values, odier thermodynamic functions, such as endialpy increments, entropies and Gibbs energy fimctions of these compounds were derived. The Cp 9g values of sodium medioxide, sodium ethoxide, sodium n-propoxide and sodium iso-propoxide were measured and reported. 

Gibbs energies, enthalpies, entropies, heat capacities, and volumes, as well as intensive properties, such as permitlivities or viscosities. The excess functions of extensive properties over those for ideal mixtures of the components, symbolized by y (or the respective increments for intensive quantities, symbolized by AT), are usually defined in terms of the mole fraction composition with respect to the pure components ... 

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