Free energy of formation from the elements

To calculate the reaction s equilibrium constant, we note that the free energy change A Gsw of each of the swap reactions in Equation 11.1 is the negative free energy of formation from the elements of the corresponding species... 

Note that the Gibbs free energy of formation from the elements of the fictive constituent oxides does not correspond to the actual thermodynamic value. It differs from it by an empirical term (4G) siiioifioation) that accounts for the structural difference between the oxide in its stable standard form and as a formal entity present in the layered silicate (cf. table 5.58). 

Table 5.59 lists Gibbs free energies of formation from the elements of mica end-members obtained with the procedure of Tardy and Garrels (1974). For comparative purposes, the same table lists Gibbs free energies of formation from the elements derived from the tabulated and S% p values (same sources as in table 5.57) by application of... 

Table 8.13 Standard partial molal Gibbs free energy of formation from the elements cal/mole), standard partial molal... 

Table 8.16 Standard molal Gibbs free energies of formation from the elements for aqueous ions and complexes and condensed phases, partly adopted in constructing the Eh-pH diagrams in figure 8.21. Data in kcal/mole. Values in parentheses Shock and Helgeson s (1988) tabulation. Sources of data (1) Wagman et al. (1982) (2) Garrels and Christ (1965) (3) Pourbaix (1966) (4) Berner (1971)...

The standard partial molal volumes (V ), heat capacities (C >), and entropies (S ) of aqueous /i-polymers, together with their standard partial molal enthalpies AHj) and Gibbs free energies of formation from the elements AGf), are linear functions of the number of moles of carbon atoms in the alkyl chains (figure 8.28). 

Table 16-1 compiles some data for S°, the molar entropy, and AGp the free energy of formation from the elements. All values in Table 16-1 are presented at 25°C and at standard states. Notice that the units of entropy and free energy are stated per mole, mol-1. This means that the moles used to balance a chemical reaction are included by the multiplication of the coefficient (mol in balanced equation) and the value from the table so that unit mol cancels. This is also the way in which we handled calculations involving AH values. 

Strategies for preparation are numerous and invoh widely differing starting metallic compounds, as we as different carbon and nitrogen sources. It is then fore instructive to consider the thermodynamics [2. of various kinds of transformations. The heats an free energies of formation from the elements at 2981 and 1000K are presented in Table 1 for carbides an Table 2 for nitrides. For illustration, different transfo mations to molybdenum carbide are presented at 2981 in Table 3 and at lOOOK in Table 4. 

Table 1. Heat and free energy of formation from the elements of transition metal carbides (Mmol-1) calculated from data in Ref. 22.

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