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INTRODUCTION TO CONDUCTOMETRIC TITRATIONS
The determination of the end point of titration by means of
conductivity measurement is known as conductometric
titrations. This method is applicable to any titration in which
there is a sharp change in conductivity at the end point.
Conductometric titrations are based on the principle that
the equivalent conductivity depends upon the number and
mobility of ions. Thus conductance method can be used to
follow the course of a titration, provided that there is a
significant difference in specific conductance between the
original solution and the reagent or the products of the
reaction.
Conductance is a non-specific physical property of
electrolyte solutions (depending on all ionic species
present), changes in conductivity are observed when one ion
is substituted by the other if the intrinsic mobilities of these
two ions differ.
Titration apparatus

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A conductivity cell or dip cell is used for conductometric
titration. The dip cell is connected to the conductivity meter
and a pen recorder can be attached to give a plot of the
change in conductance during titration.
The titration apparatus may consist of-
1.A galvanometer with rectifier to provide a visual
indication of balance point.
2.A telephone receiver for an audible indication.
3.An electronic device such as magic cathode ray tube.
4.Magnetic induction apparatus employed by Oliphant
and Freund in 1963.
Measurement- Dilute 25 cm3
of the solution to be
titrated to 100 cm3
with distilled water, and the stirrer
set in motion. The titrating agent (concentration at
least 10 times that of the solution being titrated)
should be placed in a 5 cm3
or 10 cn3
micro burette.
The reagent is stirred after each addition and allowed
to stand for a minute or two. The conductance is
measured. The addition of titrating reagent is

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continued until five readings beyond the equivalence
point have been made.
The conductance is plotted as ordinate against the
volume of the titrating as abscissa. The point of
intersection of the two straight portions of curve is
taken as the equivalence point of the reaction.
Types of conductometric titrations
Some common types of conductivity titrations are-
1.Neutralization titrations
2.Replacement titrations
3.Redox titrations
4.Precipitation titrations
5.Complexometric titrations
Neutralization titrations
Neutralization titrations are also known as Acid-base
titrations. In this method, the conductance of the hydrogen

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ions and hydroxyl ions are compared with the conductivity
of the sample solution.
1.Strong acid with strong base-
For example, take the titration of the HCl with NaOH.
[H+
Cl-
] + [Na+
OH-
] [Na+
Cl-
] + H2O
The initial conductivity of the cell HCl solution is high
because of the protons from the dissociation of the acid.
Then titrating with NaOH dissociates into Na+
and OH-
. This
hydroxyl ion reacts with the H+
ions to form the water. This
shows the decrease in the conductivity. After completion of
the reaction, the excess addition of the NaOH shows the
increase in the conductivity.
The plot between the conductivity and the volume of the
titrant shows the V-shaped curve.

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2.Strong acid with weak base-
For example, titrations of the strong acid such as HCl with
the weak base such as the ammonium hydroxide.
HCl + NH4OH NH4Cl + H2O
Same as the titration of the strong acid with strong base, it
initially shows the increase in the conductivity because of
the H+
ions. This conductivity is decreased by the addition of
the weak base that is with the NH4OH that neutralizes the H+
ions with the OH-
ions and decreases the conductivity. The
excess addition of the NH4OH does not show the change in
the conductivity.
The plot between the conductivity and the volume of titrant
shows the plateau.

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3.Weak acid with strong base-
The weak acid such as acetic acid is titrated with the strong
base such as sodium hydroxide.
CH3COOH + NaOH CH3COONa + H2O
The acetic acid dissociates to produce the H+
ions which
shows the high conductivity and is titrated with the sodium
hydroxide which is dissociated to produce the OH-
ions
which shows slight increase in the conductivity by the
formation of the CH3COONa at the equivalence point. Then
it shows the gradual increase in the conductivity by the
addition of excess titrant.
Plot a graph between the conductivity and the volume of
the titrant which shows the plateau.

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4.Weak acid with weak base-
The weak acid such as the acetic acid is titrated with the
weak base such as ammonium hydroxide.
CH3COOH + NH4OH CH3COONH4 + H2O
The acetic acid is dissociated and it combines with the
ammonium ion after dissociation of the ammonium
hydroxide. This forms the ammonium acetate salt which
shows the increase in the conductivity. After attaining the
equivalence point, the addition of the titrant does not shows
the conductivity changes.
The plot between the conductivity and the volume of the
titrant shows the plateau.

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Redox titrations
In this method, the decrease in the hydrogen ions
concentration shows the decrease in the conductivity at the
end point.
Example: The titration of the ferrous ions with the
dichromate ions.
6Fe+2
+ Cr2O7 + 14H+
6Fe+3
+ 2Cr+3
+ 7H2O

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Since the mobility of H+
ions is high, so a sharp decrease in
the conductance is expected during the initial part of the
titration. After the equivalent point, the addition of the
titrant shows the stability in the conductivity.
References
1.PHARMACEUTICAL ANALYSIS-
P.D. Chaithanya Sudha
2. BASIC CONCEPTS OF ANALYTICAL CHEMISTRY-
S.M. Khopka

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