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:
(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 the couple
is negligible, so the potential measured is that of the couple
, 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
This Demonstration was based on the electrochemistry course (Cours LC102) for first-year students at University Pierre Marie Curie (Paris).