Effects of Temperature and Pressure on Equilibrium Position

The relation of Eq. 11.8.23 does not apply to an ion, because we cannot write a formation reaction for a single ion. Instead, the relation between AfG°, AfH° and 5° is more complicated. 

Consider first a hypothetical reaction in which hydrogen ions and one or more elements form H2 and a cation M + with charge number z+  

For this reaction, using the convention that A H°, S, and AfG° are zero for the aqueous H+ ion and the fact that AfH° and AfG° are zero for the elements, we can write the following expressions for standard molar reaction quantities  

For example, the standard molar Gibbs energy of the aqueous mercury(I) ion is found 

For an anion X with negative charge number z, using the hypothetical reaction z /2 H2(g) + elements z H+(aq)-F X (aq) we find by the same method 

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CHAPTER 11 REACTIONS AND OTHER CHEMICAL PROCESSES 11.9 Effects of Temperature and Pressure on Equilibrium Position... 

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