Chemistry - Electrochemistry Question with Solution | TestHub

According to Kohlrausch's law of independent migration of ions, the molar conductivity of an electrolyte at zero concentration is given by the sum of the molar ionic conductivities of its constituent ions, each multiplied by the number of ions present in one formula unit.

The chemical formula for aluminium sulphate is ${\mathrm{Al}}_2({\mathrm{SO}}_4{)}_3$. It dissociates as:

${\mathrm{Al}}_2({\mathrm{SO}}_4{)}_3\to 2{\mathrm{Al}}^{3+}+3{\mathrm{SO}}_4^{2-}$

The molar conductivity at zero concentration for aluminium sulphate is:

${\Lambda }_m^{\circ }=2{\lambda }_{{\mathrm{Al}}^{3+}}^{\circ }+3{\lambda }_{{\mathrm{SO}}_4^{2-}}^{\circ }$

Substituting the given values:

${\Lambda }_m^{\circ }=2(189)+3(50.1)$

${\Lambda }_m^{\circ }=378+150.3$

${\Lambda }_m^{\circ }=528.3{\Omega }^{-1}{\mathrm{cm}}^2{\mathrm{mol}}^{-1}$

Answer: $528.3$