Molar Conductivity:

In order to compare quantitatively the conductivities of electrolytes, a quantity called molar conductivity is frequently used.  The molar conductivity, Λm (capital lambda) is the conductivity per unit molar concentration of a dissolved electrolyte.  It is related to conductivity, κ by the relation:

Λm  = κ/c

 where c is the concentration in mol m^-3. The molar conductivity is usually expressed in S m2 mol^-1 or S cm²  mol^-1. It may be remembered that S m2 mol-1 = 10,000 s cm² mol^-1.

It is to be remembered that c in Eq. 4.8 is to be expressed in mol m^-3 unit. If the concentration is given in terms of Molarity (mol dm^-3), then the following conversion is to be carried out

c (mol  m^-3)  =  Molarity  ×  1000

Earlier equivalent conductivit y (Λeq), which is given by the following expression, was in use

Λ_eq 1000 × κ /c

 where c is the concentration expressed in terms of normality of the solution. Unit of Λ_eq is ? ^-1 cm ² eq^-1. However, IUPAC recommends the use of molar conductivity only.