Question

Define limiting molar conductivity.

Answer 1

Molar conductivity $\;{\Lambda _m}$ gives the conductance of a solution that contains one mole of an electrolyte and the entire solution is kept in the cell containing electrodes that are one centimeter apart.
$\;{\Lambda _m} = \dfrac{{1000 \times \kappa }}{C}$
Here, $\kappa$ is the conductivity and C is the molar concentration of the electrolyte.

Complete answer:
The molar conductivity at infinite dilution is called the limiting molar conductivity. The infinite dilution is the approximately zero concentration of the electrolyte. The molar conductivity at approximately zero concentration of the electrolyte is called the limiting molar conductivity. At infinite dilution, the electrolyte is almost hundred percent ionized.
To determine the limiting molar conductivity of a strong electrolyte, you can extrapolate the graph of molar conductivity vs concentration. The limiting molar conductivity of a strong electrolyte is less than unity.
You cannot determine the limiting molar conductivity of a weak electrolyte by this method of the extrapolation of the graph. You can apply Kohlrausch law for this purpose.
Kohlrausch law states that
$\;{\Lambda _m} = \Lambda _m^0 - K\sqrt c$​
where, $\;{\Lambda _m}$ represents the molar conductivity
$\Lambda _m^0$​ represents the molar conductivity at infinite dilution
K is the Kohlrausch coefficient
and c is the concentration of the electrolyte.

Note:
A term very similar to the molar conductivity is the equivalent conductivity.
It is the conductance of a solution that contains one gram equivalent of an electrolyte and the entire solution is kept in the cell containing electrodes that are one centimeter apart.