Argentometric Titration by Precipitation of Silver Salts

Argentometric titrations are based on the use of silver cation as a precipitating agent. The objective here is to do a simple titration by precipitation and to use the titration curve to determine the solubility constant of AgI. The reaction considered is . In this Demonstration, you can change the initial concentration of , the volume of added, and the solubility product to see the changes in the titration curve.

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).