Free energy change of reaction standard

Calculate the standard free energy change of reaction ( AG ) at 873K. 

The electrical work done by Cell I under standard and reversible conditions is a measure of the standard free energy change of Reaction 13. Thus... 

In this case, however, the ISi jO component is at infinite dilution in a host of essentially pure YSi cO. Now we assume that Goldschmidt s first rule applies, i.e., we assume that if I and Y " " had exactly the same ionic radius then the standard free energy changes of reactions (1) and (4) would be the same. The actual difference between the standard free energy changes is assumed to be due to the work done in straining crystal and melt by introducing a cation which is not the same size as the site. This is a reasonable assumption for closed-shell ions such as Ca, Sr, and Mg " " and it also appears to work in those cases, such as the lanthanides, where crystal field effects are small (Blundy and Wood, 1994). For first row transition ions such as Co, and Cu, however,... 

Particular attention is paid to AG°, the standard free-energy change of reactions at pH = 7. When the sign of AG° is +, the reaction is endergonic when the sign of AG° is —, the reaction is exergonic. 

Equation 13.2 is the fundamental equation of equilibrium electrochemistry. It is derived by equating electrical and chemical work or alternatively from Nernst equation. 37-39 j( (j)a( (jjg standard free-energy change of reaction 1 can be... 

The standard free-energy change of reaction 17 can be computed from the free energy for dissociating a Hj molecnle in H atoms and the ionization potential of H". Denoting this energy by and snbstituting in Equation 13.16. we have... 

According to the definition of standard free energy of formation, the standard free energy change of reaction (2.17) is also equal to the standard free energy of formation of MO, and hence,... 

Hence, the composition of the gas mixture at equilibrium will be somewhat different from the original. As is evident from reaction (5.C.1), H2O will also be present at the equilibrium. Thus, the problem reduces to one of finding the standard free energy change of reaction (5.C.1) and calculating... 

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