Question

What will be the molar conductivity of $AL^{3+}$ ions at infinite dilution if molar conductivity of $Al_2(SO_4)_3$ is $858\, S \,cm^2 \,mol^{-1}$ and ionic conductance of $SO^{2-}_4$ is $160\, S\, cm^2\, mol^{-1}$ at infinite dilution?

• A. $189\,S\,cm^{2}\,mol^{-1}$
• B. $698\,S\,cm^{2}\,mol^{-1}$
• C. $1018\,S\,cm^{2}\,mol^{-1}$
• D. $429\,S\,cm^{2}\,mol^{-1}$

Answer 1

Answer: (A)

$\Lambda^{\circ}_{Al_2\left(SO_4\right)_3}=2\Lambda^{\circ}_{Al^{3+}}+3\Lambda^{\circ}_{So^{2-}_{4}}$
$\Lambda^{\circ}_{Al^{3+}}=\frac{\Lambda^{\circ}_{Al_2}\left(SO_{4}\right)_{3}-3\Lambda^{\circ}_{SO^{2-}_{4}}}{2}$
$=\frac{858-\left(3\times160\right)}{2}$
$=189\,S\,cm^{2}\,mol^{-1}$