Question

What is Kohlrausch's law? Explain any two applications of Kohlrausch's law.

Answer 1

Kohlrausch's law :
The value of molar conductance at infinite dilution is give by the sum of the contributions of ions (Cation and anion)
${\lambda }_m^{\infty }=x{\lambda }_{+a}^{\infty }+y{\lambda }_{-e}^{\infty }$
${\lambda }_{+2}$ and ${\lambda }_{-e}$ ionic conductance of cation and anion x and y = no. of ions.
Two applications
(i) Calculation of molar conductance at infinite dilution for weak electrolytes
${\lambda }_m^{\infty }\left(C{H}_{3}COOH\right)={\lambda }^{\infty }C{H}_{3}COO+{\lambda }_{H+}^{\infty }$
(ii) Determination of degree of dissociation of weak electrolyte. If at any concentration C the value of molar conductance is ${\lambda }_m^e$ then
$a=\frac{\lambda m^e}{{\lambda }_m^{\infty }}$
d = degree of dissociation
(iii) Dissociation constant for weak electrolvte.
(iv) Determination of solubility of sparingly soluble salt.
(v) Determination of ionic product of water.