Potentiometric and Colorimetric Titration

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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 .
Contributed by: Quang-Dao Trinh (March 2011)
Open content licensed under CC BY-NC-SA
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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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