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1. Conductometry

2. Introduction to Conductometry
Conductometry is the simplest electroanalytical techniques to measure the
conductivity of an analyte where conductivity is the ability of a medium to
carry electrical current.
The progress of a chemical reaction can be monitored to analyze ionic
species and to monitor a chemical reaction by measuring its electrolytic
conductivity.
Conductivity measurement can be performed directly by using a conductivity
meter or by performing conductometric Titrations.
Conductors are usually of 2 types:
Metallic : (flow of electrons)
Electrolyte : (movement of ions)
Conductance of electricity is the migration of positively charged ions towards
cathode and negatively charged ions towards anode. As current is carried out
by ions that’s why conductance depends on number of ions in the solution.
Conductivity is usually carried out by using a wheatstone bridge circuit and a

3. Principle
 To measure the ability of a solution to pass an electrical current
carried by cations and anions
 In solution: current is carried out by cations or anions (ions)
 In metals: current is carried out by electrons
 A solution conduct electricity depending upon many factors like
 Concentration of a solution
 Mobility of ions
 Temperature
 The solutions of electrolytes conducts electric current like a metallic
conductor thus they are said to follow Ohm’s Law.

4. Ohm’s Law
 Ohm’s law states the relationship between electric current and potential difference. The
current that flows through most conductors is directly proportional to the voltage applied.
 Ohm’s law states that the voltage across a conductor is directly proportional to the current
flowing through it, provided all physical conditions and temperatures remain constant.
 From Ohm’s law
V = IR
it is apparent that the
 Electric current (I) is inversely proportional to the resistance (R), and directly proportional to
the voltage applied (V) only if the provided temperature and the other physical factors remain
constant.

5. Conductance
 The measure of opposition/obstruction provided by a material through which current is flowing
is known as resistance.
 Conductance is the inverse of resistance, which means that it is a measure of how easily the
current will flow through the material.
 The factors on which the Conductance depends upon are as follows:
Length of the Conductor.
 When the length of the Conductor increases, the Resistance increases. Hence the Resistance is
directly proportional to the length of the Conductor and is inversely proportional to Conductivity.
R I
∝
where l is the length of the Conductor
Area of cross-section of the Conductor.
 The area of cross-section is inversely proportional to the Resistance.
R 1A
∝
where A is area of cross-section
 Principle or the process of conductance is dependent on
 Concentration of ions
 Movement of ions
 Replacement of ions (can be increased or decreased)

6. Types of Conductance

9. Conductivity Measures
 Titrant: A solution used in titration whose concentration is known and is added to another
solution of unknown concentration to determine its concentration.
 Analyte or titrand: The solution used in titration whose concentration is unknown.
 Equivalence Point: The point in conductometric titration at which conductivity undergoes a
sudden change.
 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
 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.
 Current Source: High frequency alternating current generators are used to apply potential
difference across electrodes
 Conductivity Cell: Avoid the change of temperature during determination
 Wheat stone bridge: Specific conductance is determined by using a Wheatstone bridge in
which a variable resistance is adjusted so that it is equal to the resistance of the unknown
solution between platinized electrodes of a standardized conductivity cell.
 Conductivity Meter: Measures the conductivity of the solution to confirm the end point of a
reaction. Usually these are of wide mouth and of 2 types

11. Factors affecting conductance
 Temperature: 1°C increase in temperature causes 2% increase in
conductance.
 Nature of ions: size, molecular weight and number of charges.
 Concentration of ions: by increasing number of ions conductance increases.
 Size of electrodes: conductance is directly proportional to the cross sectional
area.

12. Conductometric Titrations
 The determination of end point of a titration by means of conductivity
measurements is known as conductometric titration.
 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).
 It can be noted that the electrical conductivity of an electrolytic solution is
dependent on the number of free ions in the solution and the charge
corresponding to each of these ions.
 In this titration conductometer is used for measuring conductance. This is the
reason it does not require any indicator as conductance or

13. 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.
 Conductometric titration is based on the measurement of conductance of the solution.
The conductance of the solution (analyte + titrant) depends on following three factors:
• Number of free ions
• Charge on free ions
• Mobility of the free ions
 During titration one of the ions is replaced by the other and these two different ions
differ in their ionic conductance as well. So, conductivity of the solution differs
during the course of titration. A graph is plotted between change in conductance and
volume of titrant added. By this graph an equivalence point can be detected.

14. Theory
 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 the 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.

15. Types of Conductometric Titration
1. Precipitation Titration
 Precipitation titration is a type of titration in which the titrant is made to
react with an analyte to form a precipitate.
 During this experimentation of titration, an insoluble substance is formed
after the analytical procedure is completed and every drop of the analyte
is used for the formation of the precipitate.
 In case the titrant is in excess, it will automatically react with indicators like
potassium chromate, silver nitrate or fluorescein ions, and provide a signal
to terminate the titration procedure.
 Basically, the principle on which the precipitation titration method works is
that the amount of reagent added should be equal to the amount of the
precipitate formed.
 It is used in many pharmaceutical industries and food industries to measure
the level of the content of salt in different food and drinks.
 The precipitation titration is not conducted with just a single method. In
fact, there are three types of distinct methods that are used to carry out
this titration, namely Volhard’s method, Fagan’s method, and Mohr method.

16. Complexometric Titration
 Commonly known as chelatometric titration & is used to specify an
endpoint of a titration through the formation of a colored complex by
volumetric analysis.
 The reason replacement titration is also termed volumetric analysis is that it
involves the measurements of volumes of titrants that are reacted. The
process involves the tracing of a mixture of metal ions in the solution.
 The reaction is brought to equilibrium by adding drops of titrants in the
solution in succession.
 The most common titrant that is used is the EDTA
(ethylenediaminetetraacetic acid) titrant.
 Complexometric titration is one of the most widely used types of titrations
because it gives a very accurate identification of the equivalent points.
For the most part, this titration is used to titrate phosphates, oxalates,
and benzoates.
 The commonly used indicators in this titration method are Calmagite and
Eriochrome Black T (EBT).

17. 3. Redox Titration
 Redox titration is the type of titration which applies the oxidation-
reduction reaction. The analyte and the titrate react through this
reduction or redox technique.
 Similar to acid-base titration, the endpoint or the equivalent point in the
redox titration is known through the use of an indicator, also called a
potentiometer.
 Redox titration is one of the usual techniques used to determine and
identify the concentration of various unknown analytes in a given
solution.
 Instead of examining the concentration, it is proven to be more convenient
to examine the potential of the reaction in redox titration. Hence, it is
crucial to obtain the shape of the correlated titration curve.

18. 4. Acid Base Titrations:
Titration of strong acid
 with strong base, e.g. HCl with NaOH
 with weak base, e.g. HCl with NH4OH
Titration of weak acid
 with strong base, e.g. CH3COOH with NaOH
 with weak base, e.g. CH3COOH with NH4OH

20. 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 colored 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.

21. Applications of Conductometric Titration
Since conductometric titration is exclusively used in analytical chemistry, it
has various applications.
Mentioned below are some of its major applications:
 Conductometric titrations are used to determine water purity. It is used
to check the levels of pollution present in different small water bodies like
lakes, ponds or rivers.
 Conductometry can also be used to examine the salinity of seawater and
the alkalinity of freshwater.
 This type of titration is used by food microbiologists, to trace various
microorganisms.
 Conductometric titration can be used in determining deionized and
distilled water purity or freshness by examining the equilibrium of
chemicals in ionic reactions.
 It is also used largely in the pharmaceutical industries to detect many
antibiotics and to check the levels of basicity in various organic acids.

23. Limitations of Conductometric Titration
With various advantages, conductometric titration has few limitations as well
which are listed below
• By conductometric titration technique, only a few specific redox titrations can
be carried out.
• It shows less accurate results when the total electrolytic concentration is high
in solution. It makes it less satisfactory.
• It shows less accurate results when the total electrolytic concentration is high
in solution. It makes it less satisfactory.
• Failure to properly measure the volumes of the solutions used.