Thermodynamic Condition for a Redox Titration Reaction

The thermodynamic condition is an absolute necessity A titration reaction must be as complete as possible, regardless of the kind of titration acid-base, redox, etc. This condition must be satisfied in order to weaken the titration error (see Chap. 7). If the titration reaction is 

K° itself is connected to the potential difference A of both couples 1 and 2 by the relationship 

As we ve already noted, it is rarely realistic to use standard redox potentials to calculate equilibrium constants since the standard conditions often do not prevail. It is more judicious to use apparent standard potentials and formal potentials when they are known. In this case, the calculated equilibrium constants are no longer the thermodynamic ones, but the apparent ones. They are given by the relation 

16 Calculating Equilibrium Potentials of Solutions Containing Several Redox Couples 

In the simple case in which mi =ti2, the condition most often quoted in the literature in order for a redox tittation to be satisfactory is 

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