Specific and molar conductance

Specific and Molar Conductance

Specific and molar conductance are two important terms used to describe how well an electrolytic solution conducts electricity. These are fundamental topics in electrochemistry that provide insights into how ions behave in a solution.

Specific Conductance (κ)

Specific conductance, also known as conductivity, refers to the conductance of a solution when placed between two electrodes 1 cm apart and having a cross-sectional area of 1 cm². It is denoted by the symbol κ (kappa).

Unit: S·cm^–1

It depends on the number of free ions present in a unit volume of the solution and is affected by concentration, temperature, and nature of the electrolyte.

Molar Conductance (Λ_m)

Molar conductance is the conductance of all the ions produced by one mole of an electrolyte dissolved in a solution. It gives an idea of how efficiently an electrolyte conducts electricity per mole of solute.

Unit: S·cm²·mol^–1

It is denoted by Λ_m and calculated using the formula:

Λ_m = κ × (1000 / C)

Here, C represents the concentration of the solution expressed in moles per litre (mol·L^–1).

Variation with Dilution

• Specific Conductance (κ): Decreases with dilution because the number of ions per unit volume reduces.
• Molar Conductance (Λ_m): Increases with dilution due to decreased interionic interactions and increased ion mobility.

Conclusion

Specific conductance measures how well a solution conducts electricity per unit volume, while molar conductance measures it per mole of solute. Both are influenced by the concentration of the electrolyte and play a key role in understanding ionic behavior in solutions.