Free Gibbs energy of formation

A recent article reported equations to help calculate the heat of reaction for proposed organic chemical reactions. In that article, enthalpy equations were given for 700 major organic compounds. 

equations are given to identify whether the reactions are thermodynamically favorable. The method uses Gibbs free energy of formation for the reactants and products. 

FORMULA NAME A B c DEL GF 29aK NO. FORMULA NAME A B c DEL GF 298K 

2 CCL3F TRICHLORO- -284.764 1.3487E-01 -5.3707E-06 -245.18 47 C2H2CL2 TRANS-1.2-DI- -0.772 7.4474E-02 5.8258E-06 22.01 

3 CCL2F2 DICHLORODI -481.826 1.4482E-01 4.3398E-06 -438.06 48 C2H2CL4 1.1,2,2-TETRA- -153.859 2.2902E-01 -5.6905E-07 -85.56 

4 CCLF3 CHLOROTRI- -694.327 1.3545E-01 6.8525E-07 -653.96 49 C2H2F2 1,1-DIFLUORO- -337.271 7.8515E-02 7.9741 E-06 -313.09 

CARBON-TETRACHLORIDE TRICHLORO-FLUOROMETHANE OICHLORODI FLUOROMETHANE CHLOROTRI-FLUOROME7HANE CARBON-TETRAFLUORIDE CARBON MONOXIDE CARBON DIOXIDE CARBONYL-SULFIDE CARBON-DISULFIDE CHLOROFORM DICHLORO-FLUOROMETHANE CHLORODI-FLUOROMETHANE TRIFLUORO-METHANE TRIIODOMETHANE ISOTHIOCYANIC-ACID 

OICHLORO-METHANE CHLOROFLUORO-METHANE DIFLUORO-METHANE DIIODOMETHANE FORMALDEHYDE FORMIC-ACID BROMOMETHANE CHLOROMETHANE FLUOROMETHANE IODOMETHANE NITROMETHANE METHYL-NITRfTE METHYL-NITRATE METHANE METHANOL METHANETHIOL METHYLAMINE TETRA 

CHLOROETHENE HEXACHLORO-ETHANE 112TRICHLORO-TRIFLUOROETHANE 12DICHLORO-TETRAFLUORO-ETHANE CHLOROPENTA-FLUOROETHANE TETRAFLUORO-ETHENE HEXAFLUORO-ETHANE CYANOGEN TRICHLOROETHENE -9.886 PENTACHLORO- -143.234 ETHANE TRIFLUORO-ETHENE ACETYLENE (ETHYNE) 

---

Sodium Chlorite. The standard enthalpy, Gibbs free energy of formation, and standard entropy for aqueous chlorite ions ate AH° = —66.5 kJ/mol ( — 15.9 kcal/mol), AG = 17.2 kJ/mol (4.1 kcal/mol), and S° = 0.1883 kJ/(molK) (0.045 kcal/(molK)), respectively (107). The thermal decomposition products of NaClO, in the 175—200°C temperature range ate sodium chlorate and sodium chloride (102,109) ... 

Gibbs free energy of formation of ideal gas (AGf, kjoule/g-mol) is calculated from the tabulated coefficients (A, B, C) and the temperature (T, °K) using the following equation ... 

The change in Gibbs free energy for the reaction is determined from Equation 2 and the Gibbs free energy of formation for the products and reactants ... 

A copy (5V4 inch floppy disk) of a menu-driven computer program to calculate Gibbs free energy of formation and change in Gibbs free energy for reactions (including random access data file of compound coefficients) is available for a nominal fee. For details, contact C. L. Yaws, Dept, of Chem. Eng. Lamar University, P.O. Box 10053, Beaumont, Texas 77710, USA. 

With reference to rule (3) (Sec. 7.1.3) regarding metal atom mobility, we note that the Gibbs free energies of formation (AG( ) at 298 K for LaNi s and for LaH2 are about -67 and -171 kJ mol-1 respectively. Thus the following disproportionation reaction is highly favored [29] ... 

To find a numerical value for AHi, we need to know ArH° at one temperature, while evaluation of I requires ArG° at one temperature. The usual choice is to obtain ArH° and ArG° at T = 298.15 K from standard molar enthalpies of formation and standard molar Gibbs free energies of formation. Earlier in this chapter we referred to examples of these quantities. It is now time to define AfH° and AfG° explicitly and describe methods for their measurement. 

Standard molar enthalpies of formation, AfH°m, and standard molar Gibbs free energies of formation, Af(7, are useful, since they can be used to calculate ArH° and ArG°. The relationships are... 

Table 9.1 Standard heat capacities, entropies, enthalpies of formation, and Gibbs free energies of formation at T = 298.15 K. ...

Gibbs Free Energies of Formation A common method for obtaining AfG° makes use of the equation... 

The Gibbs free energy of formation of Cl(aq) is obtained from the following steps (again in kJ). 

We obtain K from the standard Gibbs free energies of formation. For reaction (9.85) we get... 

TABLE 7.6 Examples of the TABLE 7.7 Standard Gibbs Free Energies of Formation at 25°C (kJ-mol Ij ... 

Standard Gibbs free energies of formation can be determined in various ways. One straightforward way is to combine standard enthalpy and entropy data from tables such as Tables 6.5 and 7.3. A list of values for several common substances is given in Table 7.7, and a more extensive one appears in Appendix 2A. 

EXAMPLE 7.14 Calculating a standard Gibbs free energy of formation from enthalpy and entropy data... 

Calculate the standard Gibbs free energy of formation of HI(g) at 25°C from its standard molar entropy and standard enthalpy of formation. 

FIGURE 7.27 The standard Gibbs free energy of formation of a compound is defined as the standard reaction Gibbs free energy per mole of formula units of the compound when the compound is formed from its elements. It represents a "thermodynamic altitude" with respect to the elements at "sea level." The numerical values are in kilojoules per mole. 

The standard Gibbs free energy of formation of HI is therefore +1.69 kj-mol in good agreement with the value of +1.70 kj-tnol-1 quoted in the text. Note that, because this value is positive, the formation of pure HI from the elements at 1 bar is not spontaneous. 

Just as we can combine standard enthalpies of formation to obtain standard reaction enthalpies, we can also combine standard Gibbs free energies of formation to obtain standard Gibbs free energies of reaction ... 

---