Titration in which the end point is determined by measuring the resistance of the solution to an electric current that is passed through it.

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CONDUCTOMETRIC
TITRATION

2. INTRODUCTION OF CONDUCTOMETRY
2
conductometry is a measurement of electrolytic conductivity to monitor a
progress of chemical reaction. Conductometry has notable application in analytical
chemistry, where conductometric titration is a standard technique. In usual
analytical chemistry practice, the term conductometry is used as a synonym
of conductometric titration, while the term conductimetry is used to describe non-
Titrative applications. Conductometry is often applied to determine the total
conductance of a solution or to analyze the end point of titrations that include ions.
In this type of titration, upon the continuous addition of the titrant (and the
continuous recording of the corresponding change in electrolytic conductivity), a
sudden change in the conductivity implies that the stoichiometric point has been
reached. The increase or decrease in the electrolytic conductivity in the
conductometric titration process is linked to the change in the concentration of the
hydroxyl and hydrogen ions (which are the two most conducting ions).
The strength of an acid can be determined via conductometric titration with a
standard solution of a base. An example of a curve plotted for such a titration process
is given below.

3. 3h
The method of conductometric titration is very useful in the titration of homogeneous
suspensions or coloured solutions as these titrations cannot be done with the use of
normal chemical indicators.

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 Conductometry means measuring the conductivity of ionic solutions caused by
mobility of ions towards respective electrodes in presence of an electric field.
 Conductivity is measured by using conductometer.
Units of conductivity is mhos(Ω-1).
 Conductivity is generally measured by using a Wheatstone bridge circuit and a
conductivity cell made of platinum.
𝑅 = 𝑉/𝑖 V-potential difference in volts
i-current in amperes
𝐶 = 1/𝑅
Total conductance of the solution is directly proportional to the sum of the n individual ion
contributions .
G = cim,i

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Ohm’s Law
The magnitude of conductometric titration is based on ohm’s law.
𝒊 = 𝒆/R
where,
i = current in amperes
e = potential difference
R = resistance in ohm’s
Conductivity Measurements
1.Electrodes
Two parallel platinized Pt. foil electrodes or Pt. black with
electrodeposited a porous Pt. film which increases the surface
area of the electrodes and further reduces faradaic polarization.

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2.Primary standard solutions
Primary standard KCl solution ,at 25℃, 7.419g of KCl in 1000g of solution has a specific
conductivity of 0.01286Ω-1/cm.
3. Conductivity Cell :
Avoid the change of temperature during determination.
4.Wheat stone bridge :

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Factors Affecting Conductivity
 Size of ions
 Temperature
 Number of ions
 Charge of ions
 Specific conductivity:-It is conductivity offered by a substance of 1cm length and
1sq.cm surface area. units are mhos/cm.
 Equivalent conductivity:-it is conductivity offered by a solution containing
equivalent weight of solute in it.

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Analytical chemistry studies and uses
instruments and methods used to separate, identify,
and quantify matter. In practice, separation,
identification or quantification may constitute the entire
analysis or be combined with another method. Separation
isolates analytes. Qualitative analysis identifies analytes,
while quantitative analysis determines the numerical
amount or concentration.
Classical qualitative methods use separations such
as precipitation, extraction, and distillation.
Identification may be based on differences in color, odor,
melting point, boiling point, radioactivity or reactivity.
Classical quantitative analysis uses mass or volume
changes to quantify amount. Instrumental methods may
be used to separate samples
using chromatography, electrophoresis or field flow
fractionation. Then qualitative and quantitative analysis
can be performed, often with the same instrument and
may use light interaction, heat interaction, electric
fields or magnetic fields.
Analytical Chemical
Laboratory

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Principle
The principle of the conductometric titration process can be stated as follows –
During a titration process, one ion is replaced with another and the difference
in the ionic conductivities of these ions directly impacts the overall electrolytic
conductivity of the solution.
It can also be observed that the ionic conductance values vary between cations and
anions. Finally, the conductivity is also dependent upon the occurrence of a chemical
reaction in the electrolytic solution.
Theory
The theory behind this type of titration states that the end-point corresponding to the
titration process can be determined by means of conductivity measurement. For a
neutralization reaction between an acid and a base, the addition of the base would
lower conductivity of the solution initially. This is because the H+ ions would be
replaced by the cationic part of the base.
After the equivalence point is reached, the concentration of the ionic entities will
increase. This, in turn, increases the conductance of the solution. Therefore, two
straight lines with opposite slopes will be obtained when the conductance values are
plotted graphically. The point where these two lines intersect is the equivalence point.

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Process
For the conductometric titration of an acid with a base, the general process is as follows:
10 ml of the acid must be diluted with approximately 100 ml of distilled water (so that the
changes in the conductance brought on by the addition of the base become small).
A burette must now be filled with the base and the initial volume must be noted.
In this step, a conductivity cell must be inserted into the diluted acid solution in a way
that both the electrodes are completely immersed.
Now, the conductivity cell can be connected to a digital conductometer in order to obtain
an initial reading.
The base must now be added drop wise into the acid solution. The volume of base added
must be noted along with the corresponding change in the conductance.
A sharp increase in the conductance of the solution implies that the endpoint has been
reached. However, a few more readings must be taken after the endpoint of the titration.
These observed values must now be plotted graphically. The equivalence point can be
obtained from the point of intersection between the two lines.
The strength of the acid can now be calculated via the formula S2 = (V1S1)/10; where S2 is
the strength of the acid, V1 is the volume of base added (as per the equivalence point on
the conductometric titration graph), and S1 is the strength of the base (already known).
Here, the volume of the acid (V2) is equal to 10 ml.

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Advantages and Disadvantages of Conductometric
Titration
Some advantages of the conductometric titration process are listed below.
This process is very useful in the titrations of very dilute solutions and weak acids.
The end-point of this method of titration is very sharp and accurate when compared to a
few other titration processes.
This type of titration is applicable for solutions that are coloured or turbid, and for which
the endpoint of the titration with normal indicators cannot be observed easily by the
human eye.
Conductometric titration has numerous applications in acid-base titrations, redox
titrations, precipitation titrations, and complex titrations.
The two major disadvantages of this type of titration include:
Only a few specific redox titrations can be done with the help of this process. This is
because the conductivity of the solution is masked by relatively high hydronium ion
concentration.
The accuracy of conductometric titration is low when the concentrations of the
electrolyte are high, making the titration process unsatisfactory.

12. APPLICATIONS OF CONDUCTOMETRY
It can be used for the determination of:-
 Solubility of sparingly soluble salts
 Ionic product of water
 Basicity of organic acids
 Salinity of sea water (oceanographic work)
 Chemical equilibrium in ionic reactions
 Conductometric titration
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Conductometric Titration-:
 Introduction.
 Types of conductometric tiration.
 Advantages of conductometric tiration.

13. CONDUCTOMETRIC TITRATIONS:
 The determination of end point of a titration by
means of conductivity measurements are known
as conductometric titrations.
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14. ACID-BASE TITRATIONS
• Titration of strong acid
(a) with strong base e.g. HCl with NaOH
(b) with weak base e.g. HCl with NH4OH
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Types of conductometric titrations:

15. • Titration of weak acid
(c) with strong base e.g. CH3COOH with NaOH
(d) with weak base e.g. CH3COOH with NH4OH
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16. PRECIPITATION TITRATIONS:-
[K++Cl-]+[Ag++No3
_]
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17. REPLACEMENT TITRATIONS
 Salt of strong acid and weak base vs.
strong base
Ex: ammonium chloride vs. sodium
hydroxide
 Salt of strong base and weak acid vs.
strong acid
Eg: sodium acetate vs. hydrochloric acid
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18. 0
50
100
150
200
250
0 10 20 30 40 50
a)Salt of strong acid, weak base vs. strong base
NH4Cl+NaOH→NH4OH+NaCl
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19. 0
50
100
150
200
250
0 10 20 30 40 50
b)Salt of strong base and weak acid vs. strong acid
CH3COONa+HCl→CH3COOH+NaCl
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20. REDOX TITRATION
Titration of ferrous ions with dichromate ions:
6 Fe2++Cr2O7
2-+14H+→6Fe3++2Cr3++7H2O
0
50
100
150
200
250
300
350
400
0 10 20 30 40 50 60
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21. COMPLEXOMETRIC TITRATION
Ex.:-KCl vs. Hg(ClO4)2
 Non-aqueous titrations can also be measured
using conductometry.
Ex:-
a)titration of weak bases vs. perchloric acid in
dioxan-formic acid.
b)Titration of weak organic acids in methanol vs.
tetra methyl ammonium hydroxide in methanol-
benzene.
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RECENT DEVLOPEMNTS
In refinary industries.
Estimation of polyelectrolytic solution.
Biotechnology.
Microbiosensors for enviromental monitoring.

23. THANK YOU
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