Question

Define limiting molar conductivity.

Hint:

At infinite dilution: Interionic forces → Zero Conductivity → Maximum \(\Lambda_m^\circ = \lambda_+^\circ + \lambda_-^\circ\)

Answer 1

Concept:
Molar conductivity (\( \Lambda_m \)) increases as the solution is diluted because interionic interactions weaken. At infinite dilution, ions move independently of each other, allowing the conductivity to reach its maximum value.

Definition:
Limiting molar conductivity (\( \Lambda_m^\circ \)) refers to the molar conductivity of an electrolyte at infinite dilution. At this point, each ion contributes independently to the total conductivity, with no interionic interactions affecting their movement.
Mathematically, it is expressed as: \[ \Lambda_m^\circ = \lambda_+^\circ + \lambda_-^\circ \] where:

• \( \lambda_+^\circ \) = limiting molar conductivity of the cation
• \( \lambda_-^\circ \) = limiting molar conductivity of the anion

Explanation:
At infinite dilution:

• The attraction between ions becomes negligible.
• The ions attain their maximum mobility, moving independently.
• The total conductivity is the sum of the individual contributions of the ions.

Therefore, \( \Lambda_m^\circ \) represents the maximum molar conductivity of an electrolyte.