KOHLRAUSCH'S LAW

KOHLRAUSCH'S  LAW :-

     “At infinite dilution, when dissociation is complete, each ion makes a definite contribution towards equivalent conductance of the electrolyte irrespective of the nature of the ion with which it is associated and the value of equivalent conductance at infinite dilution for any electrolyte is the sum of contribution of its constituent ions", i.e., anions and cations.      

 The mathematical expression of molar conductivity of the given solution at infinite dilution is:

#. Application :-

1.) Calculation of degree of ionisation and ionisation constant:

Degree of ionisation ‘∝’ =  Λ_{m /  Λ⁰m}

Λ_m   = molar conductance at any conc.

Λ⁰_m = molar conductance at infinite dilution

∝ =  Λ_{eq /  Λ⁰eq}

ionisation constant= C ∝2 /(1 -∝).

2.) Calculation of solubility product of sparingly soluble salt-

Λ_{eq = K x 1000 /C}

C = conc. of solution or molarity

Since solution is very dilute so,

Λ_{eq =   Λ⁰eq}

  _{Λ⁰eq = K x 1000 / C.}

_{3.) To determine degree of dissociation of weak acid and weak base.}

4.) To determine limiting molar conductance of weak base/ acid/ electrolyte.

#. Uses of Kohlrausch’s law :-

• Calculation of Degree of dissociation.
• Calculation of solubility of sparingly soluble salt.
• Calculation of Dissociation Constant for week electrolytes.
• Calculation of Molar Conductivity for week electrolytes at infinite dilution.