Standard free energy of formation AGf

These equations are not very useful in practice because, as remarked earlier, we do not know the absolute values of the molar free energies of substances. However, we can use the same technique we used to find the standard reaction enthalpy in Section 6.19, where we assigned each compound a standard enthalpy of formation, AHf°. We can also tabulate free energies of formation of substances and then use them to calculate AGr°. The standard free energy of formation, AGf°, of a substance is the standard reaction free energy per mole for the formation of a compound... 

The chemical basis for the various separations used in this pyrochemical process is the differences in the partitioning of uranium, plutonium, and the fission product elements between molten salt and liquid alloy phases. This difference in partitioning is largely determined by the values of the standard free energy of formation (AGf°) of the chlorides of uranium, plutonium, and the fission product elements. 

Develop a more rigorous equation for Kp as a function of the absolute temperature (K). The following standard free energy of formation (AGf), standard heat of formation, and heat capacity data are provided. 

Standard free-energy of formation (AGf). The free-energy change when 1 mole of a compound is synthesized from its elements in their standard states. (18.4)... 

The standard free energy change for a reaction can be determined from the standard free energies of formation (AGf) of the reactants and products ... 

What is the standard free energy change, AG°, for a reaction What is the standard free energy of formation, AGf, for a substance How are AGf values used to calculate AG° How can you use Hess s law to calculate AG How can you use AN° and AW values to calculate AG Of the functions AN°, AW, and AG°, which depends most strongly on temperature When AG° is calculated at temperatures other than 25°C, what assumptions are generally made concerning AH° and AW ... 

The molecular hydrides, formed by nonmetals and metalloids, are either gases or liquids under standard conditions. The simple molecular hydrides are listed in FIGURE 22.6, together with their standard free energies of formation, AGf. (Section 19.5) In each family the thermal stability (measured as AGf) decreases as we move down the family. (Recall that the more stable a compound is with respect to its elements under standard conditions, the more negative AGf is.)... 

Recall that we defined standard enthalpies of formation, AHf, as the enthalpy change when a substance is formed from its elements under defined standard conditions. oGo (Section 5.7) We can define standard free energies of formation, AGf, in a similar way AGf for a substance is the free-energy change for its formation from its elements under standard conditions. As is summarized in Table 19.2, standard state means 1 atm pressure for gases, the pure solid for solids, and the pure liquid for liquids. For substances in solution, the standard state is normally a concentration of 1 M. (In very accurate work it may be necessary to make certain corrections, but we need not worry about these.)... 

The Standard Free Energy of Formation Another way to calculate is with values for the standard free energy of formation (AGf) of the components AG° is the free energy change that occurs when 1 mol of compound is made/ram its elements, with all components in their standard states. Because free energy is a state function, we can combine AG values of reactants and products to calculate AG xn no matter how the reaction takes place ... 

We use the standard free energy of formation (AGf) to calculate AG° at 298 K. The maximum work a system can do is never obtained from a real (irreversible) process because some free energy is always converted to heat. 

Free-energy changes are often recorded as STANDARD free ENERGIES OF FORMATION, AGf (analogous to AHf, page 65). AGf is AG for the reaction in which 1 mole of tiie substance is formed from its elements in their stable forms. 

Standard free energies of formation, AGf°, for a variety of substances are given in Appendix 2A. 

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