Conductometry is an electrochemical method of analysis involve the measurement of the electrical conductivity of a solution. The conductance is defined as the current flow through the conductor. In other words, it is defined as the reciprocal of the resistance.

1. Presentation
on
CONDUCTOMETRY
by
Mr. A. B. Roge
Department of Pharmaceutical Chemistry
NANDED PHARMACY COLLEGE,
NANDED-431605

2. Contents
• Introduction
• Principle
• Important terms
• Conductometric titration
Principle
Neutralization titrations
• Applications
• References
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3. Introduction
• Conductometry is an electrochemical method of analysis involve the
measurement of the electrical conductivity of a solution. The conductance is
defined as the current flow through the conductor.
• In other words, it is defined as the reciprocal of the resistance.
• The unit for the conductance is Seimens (S) which is the reciprocal of Ohm's
(Ω−1).
• Electric conductivity of an electrolyte solution depends on:
Type of ions
Cations, anions, singly or doubly charged
Concentration of ions
Temperature
Mobility of ions
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4. Principle
 The main principle involved in this method is that the movement of the
ions creates the electrical conductivity. The movement of the ions is mainly
depended on the concentration of the ions.
 A+B− + C+D− AD + C+B−
 Where A+B− is the solution of strong electrolyte; C+D− is the solution of the
reagent.
 This replacement of the ions with the other ions shows the conductance
increase or decrease.
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5. Important Terms
 Ohms law: The law stating that electric current is directly proportional to
voltage and inversely proportional to resistance.
I = V ⁄ R
 Conductance (G): An ease with which current flows per unit area of
conductor per unit potential applied & is reciprocal to resistance(R)
G = I ⁄ R o
 Specific conductance (K): Conductance of the body of uniform length 1
cm(L) & uniform area cross section(A) 1 cm2
K = L ⁄ A
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6.  Molar conductance: (^) : Conductance of a solution containing 1 mole of the
solute in 1000 cm3 (mL) of the solution which placed between two parallel
electrodes which are 1 cm apart .
^ = 1000 ⁄ C
 Equivalent conductance: (^eq) Specific conductance of the solution containing
1gm equivalent of solute in 1000cm3(mL) of solution.
^eq =1000K ⁄ Ceq
 Resistance (R): It is a measure of the conductors oppose to the flow of electric
charge
R =1/G
 Specific resistance :(ρ) It is resistance offered by a conductor of unit length (1
cm) and having unit cross section 1 cm2.
R ∞ l ⁄ A
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7. Conductometric titration is based on the measurement of conductance of the solution. The
conductance of the solution (analyte + titrant) depends on following three factors –
The number of free ions
The charge on free ions
The mobility of the free ions
When solution of an electrolyte (Titrant) is added to solution of another electrolyte (Titrate),
overall conductance will change due to substitution of one ion of titrate(replaced ion) with ion of
titrant (replacing ion). Change in conductance depends upon mobility of replacing ion in relation
to replaced ion.
If the mobility of replacing ion is greater / lesser than replaced ion, conductance will increase /
decrease. Conductance continuously vary in same order with addition of titrant until the end of
reaction, then conductance may suddenly increased due to the excess titrant if it is strong
electrolyte and remains constant for weak electrolyte.
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Principle:

8. Neutralization titration
Strong Acid-Strong Base (HCL Vs NaOH)
• Initial fall in conductance due to replacement of high mobility Hydrogen
ions by less mobility sodium ions till end point
• Further, rise in conductance due to increase in hydroxyl ions
HCl + NaOH NaCl + H2O
Fig.1 Conductometric titration of strong acid (HCl) Vs. strong base
(NaOH)
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9. Strong acid- weak base (HCL Vs NH4OH)
• Initial fall in conductance due to replacement of high mobility hydrogen
ion by less mobility ammonium ions.
• Conductance remain constant due to suppression of NH4OH by NH4CL
HCl + NH4OH NH4Cl + H2O
Fig.2 Conductometric titration of a strong acid (HCl) Vs. weak base
(NH4OH)
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10. Weak acid –Strong base (CH3COOH Vs NaOH )
• Initial decrease in conductance followed by increase due to dissociation of salt
sodium acetate result in increase in ionic concentration
• Steep rise due to excess of NaOH
CH3COOH + NaOH CH3COONa + H2O
Fig.3 Conductometric titration of a weak acid (CH3COOH) Vs. strong base
(NaOH)
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11. Weak acid- weak base (CH3COOH Vs NH4OH)
• Initial decrease in conductance followed by increase due to dissociation of salt
sodium acetate result in increase in ionic concentration
• Constant conductance due to suppression of NH4OH by CH3COOH
CH3COOH + NH4OH CH3COONH4 + H2O
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Fig. 4 Conductometric titration of a weak acid (CH3COOH) Vs.
weak base (NH4OH)

12. • Titration of mixture of mixture of strong acid and weak
acid with as strong base:
In the presence of strong acid, the dissociation of a weak acid is completely
suppressed due to common ion effect. Therefore, addition of a base to such a
mixture will first result in the neutralization of the strong acid. The weak acid starts
reacting only after neutralization of strong acid. In the titration graph, the curve AB
represents the neutralization of strong acid, the curve BC represents the
neutralization of weak acid and curve CD represents the excess base added.
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Fig. 5 Conductometric titration of mixture of strong & weak acid
weak acid Vs. strong base

13. Applications
• Determination of solubility of an electrolyte
• Determination of water purity & salinity of sea water
• Study of chemical kinetics
• Determination of basicity of organic acids
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14. References:
• Kasture A.V. and Mahadik K.R.; (2010), Pharmaceutical Analysis. Vol. II.
Instrumental methods;19th ed. Nirali Prakashan, 124-131.
• Chatwal G. R, and Sham K. A.; (2002), Instrumental Methods of Chemical
Analysis ; 5th ed. Mumbai: Himalaya publishing house, 2.626-2.636.
• https://en.wikipedia.org/wiki/Conductometry
• https://www.tau.ac.il/~chemlaba/Files/conductometry-titrations.pdf
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