Titrations can be based on redox reactions. The objective here is to do a simple titration and use the titration curve to deduce the concentration and standard potentials of the redox couples—a potentiometric titration. The reaction considered is .
The following shows how to determine equivalence by colorimetry using a color indicator.
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 .
When , the concentration of the couple is negligible, so the potential measured is that of the couple /:
.
When , the couple determines the measured potential:
.
The change of the 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 was based on the electrochemistry course (Cours LC102) for first-year students at University Pierre Marie Curie (Paris).
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