Details

The following shows how to determine the solubility constant of the precipitation reaction.

With the volume of (in mL) added to the solution of at the unknown initial solution , we have the following results:

Here (in mL) is the volume of the solution of .

(in mol/L) is the unknown concentration of that we need to find.

(in mol/L) is the known concentration of .

(in mL) is the volume of used to reach equilibrium with .

The concentration of is then deduced by the potential of the couple /Ag. When , the potential measured depends on the concentration of in the solution:

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When , we have ; then . One can use the potential at the equilibrium to calculate the solubility constant .

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When , :

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The change of potential near the equivalence point can be used to determine the equilibrium volume . Then the unknown concentration can be calculated using (mol/L).

This Demonstration is based on the electrochemistry course (Cours LC102) for first-year students at University Pierre Marie Curie (Paris).