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Conductometric Titration
General Chemistry Lab Assignment
10/10/2016
Rabia Aziz BS-II(Chemistry)

2. Contents:
1. Introduction
Conductance
Electrolytes, Strong Electrolyte, Weak Electrolytes
Specific Conductance
Molar conductance
Equivalent Conductance
Dilution
2. Conductometric Titration
3. Conductometric titrationCurves
Discussion
4. Advantages of Conductometric Titration
5. Application of Conductometric Titration
6. Conclusion

3. Abstract: Conductometric titration is a type of titration in which the electrolytic
conductivity of the reaction mixture is continuously monitored as one reactant is added. The
equivalence point is the point at which the conductivity undergoes a sudden change. Marked
increases or decrease in conductance are associated with the changing concentrations of the
two most highly conducting ions—the hydrogen and hydroxyl ions.The method can be used for
titrating coloured solutions or homogeneous suspension (e.g.: wood pulp suspension), which
cannot be used with normal indicators. The conductometric titration curve is a plot of the
measured conductance or conductivity values as a function of the volume of the solution
added. The titration curve can be used to graphically determine the equivalence point.
1. Introduction:
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.
Conductance:The powerof electrolytesto conductelectriccurrentsistermedconductivityor
conductance.
G = I/R
Unit of Conductance: Siemens(S)
The conductance of the solutionmainly depends on two factors:
1.Size of the ions: The conductivity of the solution is inversely proportional to the size of the
ions .If the size of the ions is increasing then the conductivity of the solution will decrease
because the mobility of the ions will decrease by increasing the size of the ions.
2. Temperature: By increasing the temperature, the mobility of the ions in the solution will
increase. So temperature has a direct effect on conductance of solution. E.g. by increasing the
temperature the conductance will increase and vice versa.
Conductance Increases When:
1. Greater charge of ions
2. Smaller size of ions
3. Higher concentration of ions
4. Lower resistance of the solution

4. Electrolytes:are electrovalent substances that form ions in solution which conduct an
electric current.
Electrolysis: the phenomenon of decomposition of an electrolyte by passing electric
current through its solution is termed electrolysis.
Electrolytic Cell: contains water solution of an electrolyte in which two metallic
rodes(electrodes) are dipped.
Strong Electrolyte:Astrong electrolyteis a solute that completely, or almost completely,
ionizes or dissociates in a solution. Strong acids, strong bases and mostly salts are strong
electrolytes. They are good conductors of electricity and have a high conductanceeven at low
concentration. Example:NaCl , HCl , HNO3, H2SO4, KCl , CuSO4 , ZnSO4 etc.
Weak Electrolyte:A weak electrolyte is a substance which forms ions in an aqueous
solution but does not dissociate completely. When dissolved, a weak electrolyte does not
disperse completely into ions. The solution instead contains both ions and molecules. They
have low value of equivalent conductance. Weak acids, weak bases and few salts are weak
electrolytes. Examples: HF, HC2H3O2 (acetic acid), H2CO3 (carbonic acid), H3PO4 (phosphoric
acid),
Specific Conductance (K): It is defined as “The conductance of one centimeter cube(cc)
of a solution of an electrolyte.”
Specific Conductance Increases with:
1. Ionic concentration
2. Speed of the ions
Units of Specific Conductance: ohm-1 cm-1, S cm-1
Molar conductance(u):it is defined as the conductance of all ions produced by one mole
(one gram molecular weight) of an electrolyte when dissolved in a certain volume (cc).
U= K*100/ M
Equivalent Conductance (A): it is defined as the conductance of an electrolyte
obtained by dissolving one gram equivalent of it in volume (cc) of water.
A = K V

5. Dilution: The volume of water in which a certain amount of the electrolyte is dissolved is
always measured in cubic centmeters (cc) and this is known as dilution.
2. Conductometric Titration:Conductometric titration is a type of titration
in which the electrolytic conductivity of the reaction mixture is continuously monitored as
one reactant is added. The equivalence point is the point at which the conductivity
undergoes a sudden change.
The principle of conductometric titration is based on the fact that during the titration, one of
the ions is replaced by the other and invariably these two ions differ in the ionic conductivity
with the result that conductivity of the solution varies during the course of titration. The
equivalence point may be located graphically by plotting the change in conductance as a
function of the volume of titrant added.
In order to reduce the influence of errors in the conductometric titration to a minimum, the
angle between the two branches of the titrationcurve should be as small as possible. If the
angle is very obtuse, a small error in the conductance data can cause a large deviation. The
following approximate rules will be found useful.
•The smaller the conductivity of the ion which replaces the reacting ion, the more
accurate will be the result.
•The larger the conductivity of the anion of the reagent which reacts with the
cation to be determined, or vice versa, the more acute is the angle of titration
curve.
•The titration of a slightly ionized salt does not give good results, since the conductivity
increases continuously from the commencement. Hence, the salt
present in the cell should be virtually completely dissociated; for a similar
reason; the added reagent should also be as strong electrolyte.
Conductometric Titration Curves are:
1.Strong Acid with a Strong Base, e.g. HCl with NaOH:
Before NaOH is added, the conductance is high due to the presence of highly mobile hydrogen
ions. When the base is added, the conductance falls due to the replacement of hydrogen ions
by the added cation as H+ions react with OH− ions to form undissociated water. This decrease in
the conductance continues till the
equivalence point. At the equivalence point, the solution contains only NaCl. Afterthe
equivalence point, the conductance increases due to the large conductivity of OH-ions.

6. 2. Weak Acid witha Strong Base,e.g. acetic acid with NaOH:
Initially the conductance is low due to the feeble ionization of acetic acid. On the addition of
base, there is decrease in conductance not only due to the replacement of H+ by Na+ but also
suppresses the dissociation of acetic acid due to common ion acetate. But very soon, the
conductance increases on adding NaOH as NaOH neutralizes the un-dissociated CH3COOH to
CH3COONa which is the strong electrolyte. This increase in conductance continuesraise up to
the equivalence
point. The graph near the equivalence point is curved due the hydrolysis of salt CH3COONa.
Beyond the equivalence point, conductance increases more rapidly with the addition of NaOH
due to the highly conducting OH−.
Conductometric titration of a weak acid (acetic acid) vs. a strong base (NaOH)

7. 3. Strong Acidwith a Weak Base, e.g. sulphuric acid with dilute ammonia:
Initially the conductance is high and then it decreases due to the replacement of H+. But after
the endpoint has been reached the graphbecomes almost horizontal, since the excess aqueous
ammonia is notappreciably ionised in the presence of ammonium sulphate.
4. Weak Acid witha Weak Base:
The nature of curve before the equivalence point is similar to the curve obtained by
titratingweak acid against strong base. After the equivalence point, conductance virtually
remains same as the weak base which is being added is feebly ionized and, therefore, is not
much conducting.
Conductometric titration of a weak acid (acetic acid) vs. a weak base (NH4OH)

8. Discussion: Upon dilution specific conductance decreases, while equivalent conductance
and molar conductance increases.
Increase in equivalent conductance in case of a weak electrolyte is due to increase in the
number of ions.
Advantages of Conductometric Titration:
The main advantages to the conductometric titration are its applicability to very dilute, and
coloured solutions and to system that involve relative incomplete reactions.
Application of Conductometric Titration:
It can be used for acid base, redox, precipitation, or complex titrations.
Determination of sulphur dioxide in air pollution studies.
Determination of soap in oil.
Determination of accelerators in rubber.
Determination of total soap in latex.
Specific conductance of water.
Conclusion:
The electrical conductance of a solution is a measure of the solution’s ability to conduct
electricity. The ability of a solution to conduct electric current decreases as the resistance of the
solution increases. Electricity is conducted in a solution by ions of electrolytes. Conductance of
electrolytes increases with the increase of temperature and concentration of electrolytes. The
conductance of a solution is the sum of the conductance of all the ions in the solution. The
conductance of an ion in solution is related to the charge, size and concentration of the ion.
Conductometry can be used to locate the end point of the titration. Conductometric titration is
useful for acid-base, precipitation, and complexation titrations.
REFERENCE:
1. Introduction to Chemical Analysis, Robert D.Braun
2. Fundamental of Analytical Chemistry, Skoog,west.
3. Essentials of Physical Chemistry,Arun Bahl,B.S.Bahl,G.D.Tull
4. www.tau.ac.il/.../Files/conductometry-titrations.pdf
5. https://www.reference.com/.../definition-weak-electrolyte-3b8e99e7130207...
6. https://www.stolaf.edu/depts/chemistry/courses/.../elec.htm
7. www.citycollegiate.com/chapter3b.htm
8. https://en.wikipedia.org/wiki/Molar_conductivity