The conductivity of a solution is defined as the conductance of a solution of 1 cm length and having 1 sq. cm as the area of cross-section.
Molar conductivity of a solution at a dilution (V) is the conductance of all the ions produced from one mole of the electrolyte dissolved in V cm³ of the solution when the electrodes are one cm apart and the area of cross-section of the electrodes is so large that the whole of the solution is contained between them. It is usually represented by Λ_m.
The conductivity of a solution (both for strong and weak electrolytes) decreases with a decrease in the concentration of the electrolyte, i.e., on dilution. This is due to the decrease in the number of ions per unit volume of the solution on ‘ dilution. The molar conductivity of a solution increases with a decrease in the concentration of the electrolyte. This is because both the number of ions, as well as the mobility of ions, increases with dilution. When concentration approaches zero, the molar conductivity is known as limiting molar conductivity.