Question

State and explain Kohlrausch's Law and its applications in calculating molar conductivity at infinite dilution.

Hint:

Remember: At infinite dilution, ions act independently—this is the key idea of Kohlrausch’s Law.

Answer 1

Concept: Kohlrausch’s Law states that at infinite dilution, each ion contributes independently to the total molar conductivity of an electrolyte.
Answer:
Kohlrausch’s Law:
At infinite dilution, the molar conductivity of an electrolyte is equal to the sum of the individual ionic conductivities of its cations and anions. \[ \Lambda_m^\circ = \lambda_+^\circ + \lambda_-^\circ \] where \( \Lambda_m^\circ \) is molar conductivity at infinite dilution, and \( \lambda_+^\circ \), \( \lambda_-^\circ \) are ionic conductivities.
Explanation:
At infinite dilution, ions are so far apart that interionic interactions are negligible. Hence, each ion contributes independently to conductivity.
Applications:

• Calculation of molar conductivity of weak electrolytes: Using values of strong electrolytes.
• Determination of degree of dissociation: Helps in finding dissociation of weak electrolytes.
• Calculation of solubility of sparingly soluble salts.
• Determination of ionic conductivities.

Thus, Kohlrausch’s Law is important in understanding ionic behavior in dilute solutions.