Kholraush law

Kohlrausch law of independent migration of ions

• The Kohlrausch law of independent migration of ions states that limiting molar conductivity of an electrolyte can be represented as the sum of the individual contributions of the anion and cation of the electrolyte.

• Limiting equivalent molar conductivity of an electrolyte is the algebraic sum of limiting molar equivalent conductivities of its constituent ions.

• Mathematically,

Where λ_o⁺ = limiting equivalent conductivities of cation

λ_o^- = limiting equivalent conductivities of anion.

Kohlrausch’s law of independent migration of ions states molar conductivity of an electrolyte at infinite dilution can be expressed as the sum of the contribution of individual ions. If molar conductivity of cations and anions are represented by λ^∞₊ and λ^∞_– respectively.



where v₊ and v_– are number of cations and anions per formula of electrolyte e.g.,

Λ^∞ CaCl₂ = λ^∞ (Ca²⁺) + 2 λ^∞ (CI^–)
Λ = KCl = λ^∞ (K⁺) + λ^∞ (CI^–)

Uses 1. It is used to find molar conductivity of weak electrolyte at infinite dilution which
cannot be obtained by extrapolation.

2. It is used to calculate degree of dissociation of weak electrolyte at a particular concentration.
Degree of dissociation 
where Λ^e_m is molar conductivity of weak electrolyte at a particular concentration and Λ^e_mis molar conductivity of weak electrolyte at infinite dilution.