ELECTRICAL CONDUCTION OF ELECTROLYTIC SOLUTION

ELECTRICAL CONDUCTION OF ELECTROLYTIC SOLUTION

1.1 Resistivity and Conductivity of Electrolyte Solutions

Like solid conductors, the conduction of electric current by electrolytic solutions obeys Ohm’s Law. The resistance, R of any electrical conductor is proportional to its length, l and inversely proportional to its cross-sectional area, A, i.e.

R                                                                                                                     (1)

or

R                                                                                                                     (2)

where the proportionality constant  is called the resistivity of the conductor of cell of unit length and unit cross-section area.

Re-writing eqn. (2)

                                                                                                            (3)

Hence the units of are (resistance) (length)

In chemistry in general and in electrochemistry in particular, the main interest is. the conductance rather than the resistance of electrolytic solutions. Conductance (L) and resistance R are reciprocally related, i.e.

L=                                                                                                                   (4)

The units of conductance are (ohm)^-1 sometimes called Mho or Siemens S. Similarly, we may define conductivity (or specific conductance), K, as the reciprocal of resistivity, i.e.

K=                                                                                                                   (5)

K therefore has units (resistance)^-1 (length)^-1. The specific conductivity is the current flowing through a solution placed between electrodes one unit apart and of unit cross-sectional area