Gibbs energy of formation

The entropy increase when 1 mol of liquid water evaporates to give vapor at 0.9 atm pressure is. thus 

Since this is a negative quantity, the vaporization process is spontaneous. 

In Chapter 4 we dealt with enthalpy changes in chemical reactions and found that it was very useful to determine enthalpies of formation of compounds the standard enthalpy of formation, AH, is the enthalpy increase for the process in which a compound is formed, at one atmosphere pressure, from the elements in their standard states. If we know the standard enthalpies of formation of all compounds in a chemical reaction it is a simple matter see equation 4.31) to calculate the enthalpy change in the reaction. 

The standard Gibbs energies of formation of glucose, ethanol, and carbon dioxide are given in Table 4.1. 

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Table 6.1 Enthalpies and Gibbs Energies of Formation, Entropies, and Heat...

ENTHALPIES AND GIBBS ENERGIES OF FORMATION, ENTROPIES, AND HEAT CAPACITIES... 

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. 

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