Conductance of electrolytic solution

Conductance of Electrolytic Solution

The conductance of an electrolytic solution refers to its ability to conduct electricity through the movement of ions. Electrolytic solutions are formed when ionic compounds dissolve in water, dissociating into positive and negative ions that carry electric current.

Why Conductance Occurs

When a voltage is applied across electrodes immersed in an electrolyte, ions move toward oppositely charged electrodes. This flow of charged particles constitutes electric current. Conductance increases with both the quantity and mobility of ions present in the solution.

Important Terms

• Electrolyte: A substance that conducts electricity when dissolved in water by producing ions.
• Conductance (G): The reciprocal of resistance (G = 1/R), measured in siemens (S).
• Specific Conductance (κ): Conductance of 1 cm³ of the solution placed between two electrodes 1 cm apart. Unit: S·cm^–1.
• Molar Conductance (Λ_m): Conductance of all the ions produced by one mole of an electrolyte in solution. Unit: S·cm²·mol^–1.

Factors Affecting Conductance

• Concentration of the solution: Dilution generally increases molar conductance as ion mobility increases.
• Nature of the electrolyte: Strong electrolytes fully ionize in solution, whereas weak electrolytes undergo only partial ionization.
• Temperature: Higher temperatures increase ion mobility, thus enhancing conductance.
• Nature of solvent: Solvents with high dielectric constant support better ionization and conductance.

Kohlrausch’s Law

Kohlrausch’s Law states that the molar conductance of an electrolyte at infinite dilution is the sum of the individual ionic conductances of its ions.

Λ_m⁰ = λ⁰₊ + λ⁰_–

Applications

• Used to determine the strength and nature (strong/weak) of electrolytes.
• Helps in calculating the degree of dissociation and dissociation constant.
• Important in water purity tests and electrochemical analysis.

Conclusion

In electrochemistry, the conductance of electrolytic solutions is influenced by factors such as ion concentration, ion mobility, temperature, and the type of electrolyte used. Understanding conductance helps explain the behavior of ionic compounds in solution and is essential in practical applications like batteries, electrolysis, and chemical analysis.