Enthalpy and Gibbs Energy of Formation at

Table B7 Standard enthalpies and Gibbs energies of formation at 298.15 K...

Table C.4 Standard Enthalpies and Gibbs Energies of Formation at 298.15 K (25°C)...

The tables in this section contain values of the enthalpy and Gibbs energy of formation, entropy, and heat capacity at 298.15 K (25°C). No values are given in these tables for metal alloys or other solid solutions, for fused salts, or for substances of undefined chemical composition. 

References (20, 22, 23, 24, 29, and 74) comprise the series of Technical Notes 270 from the Chemical Thermodynamics Data Center at the National Bureau of Standards. These give selected values of enthalpies and Gibbs energies of formation and of entropies and heat capacities of pure compounds and of aqueous species in their standard states at 25 °C. They include all inorganic compounds of one and two carbon atoms per molecule. 

TABLE 2-221 Enthalpies and Gibbs Energies of Formation, Entropies, and Net Enthalpies of Combustion of Inorganic and Organic Compounds at 298.1 5 K... 

Here the standard state for the ionic species is a 1-molal ideal solution the enthalpies and Gibbs energies of formation for some ions in this standard state at 25 C are given in Table 13.1-4. In Eq. 13.1-27 the standard state for the undissodated molecule has also been chosen to be the ideal 1-molal solution (see Eq. 9.7-20), although the pure component state could have been used as well (with appropriate changes in AfG, b aA B ). Finally, we have used the mean molal activity coefficient, y , of Eq. 9.10-11. Also remember that for the 1-molal standard state, y ° 1 as the solution becomes veiy dilute in the component. 

This table contains standard state thermodynamic properties of ions and neutral species in aqueous solution. It includes enthalpy and Gibbs energy of formation, entropy, and heat capacity, and thus serves as a companion to the preceding table, Standard Thermodynamic Properties of Chemical Substances . The standard state is the hypothetical ideal solution with molality m = 1 mol/kg (mean ionic molality in the case of a species which is assumed to dissociate at infinite dilution). Further details on conventions may be found in Reference 1. 

The 1978 publication is a 456 page monograph containing selected values for the entropy, molar volume, and for the enthalpy and Gibbs energy of formation for the elements, 133 oxides, and 212 other minerals and related substances at 298.15 K. Thermal functions are also given for those substances for which heat-capacity or heat-content data are available. The thermal functions are tabulated at 100 K intervals for temperatures up to 1800 K. The monograph includes detailed references to the source literature and a compound index. 

Stull, Westrum, and Sinke have searched the literature up to January 1966 for thermodynamic data. The heat capacity, entropy, enthalpy, and Gibbs energy of formation have been tabulated for 741 organic compounds in the ideal gas state at temperatures from 298 to 1000 K. The entropy, enthalpy, and Gibbs energy of formation are presented as fully as possible for 4400 organic compounds in the ideal gaseous and condensed states at 298 K. 

Ions in solntions are characterized by several thermodynamic quantities, including the standard molar heat capacities (at constant pressure) and entropies. Other important qnantities are the standard molar enthalpy and Gibbs energy of formation of the ions in solntion from the elements. As said earUer, in all these measures, it is possible to deal experimentally only with entire electrolytes or with such sums or differences of ions that are nentral. The assignment of absolute values to individual ions requires the splitting of the electrolyte values by some extra thermodynamic assumption that cannot be proved or disproved within the framework of thermodynamics. 

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