Conductometry
Contents
• Conductometry
• Principle involved
• Measurement of conductivity
• Pros and cons of conductometric titrations
• Precautions to be taken
• Procedure
• Comparison of potentiometry vs conductometry
• Applications
Objectives
By the end of this
session, students will be able to:
• Define conductometry
• Define and explain the principle involved in
conductometric titrations
• Discuss the pros and cons Conductometry
• Explain precautions to be taken for conductometric
titrations
• Brief the applications of conductometric titrations
Conductometry
• Measurement of conductivity of a solution
• Due to mobility of cations and anions towards respective
electrodes
• Conductivity (C) is inversely proportional to resistance
(R) of a solution
C = 1/R
• Unit of conductivity is mhos or ohms-1
• Conductivity of a solution depends upon-
o
Number of ions (concentration)
o
Charge of ions
o
Size of ions
o
Temperature
• Resistance of a solution is given by
R = E/I
Where E = potential difference
I = current which flows through
Unit of resistance (R) is ohms
Potential difference (E) is volts
Current (I) is amperes
• Resistance of a solution depends upon length (l) and cross
resistance (a) of the conductor through which conductivity takes place
R = ρl/a
• ρ is specific resistance
• Specific resistance
(ρ) is the resistance offered by a substance of 1cm length and 1 sq.cm
surface area, Unit of measurement is ohm cm
• Specific
conductivity (kv) is the conductivity offered by a substance of 1cm length
and 1 sq.cm surface area, Unit of measurement is mhos cm-1
• Equivalent
conductivity (λv) is the conductivity of a solution containing equivalent
weight of the solute between electrodes 1 cm and 1 sq.cm, Unit of measurement
is mhos cm-1
• Molar conductivity
(μv) is the conductivity of a solution containing molecular weight of the
solute between electrodes 1 cm apart and 1 sq.cm surface area
• Molar conductivity = specific conductivity x volume of
solution containing one molecular weight of the electrolyte
Measurement
of Conductivity
• Conductivity may be measured by applying an alternating
electrical current (I) to two electrodes immersed in a solution and measuring
the resulting voltage (V)
• Cations migrate to the negative electrode, the anions to
the positive electrode and the solution acts as an electrical conductor
