Question

Which of the following expressions correctly represents the equivalent conductance at infinite dilution of $A{l}_2(S{O}_4{)}_3$? Given that ${\Lambda }_{A{l}^{3+}}^o$ and ${\Lambda }_{S{O}_4^{2-}}^o$ are the equivalent conductances at infinite dilution of the respective ions.

• A. $2{\Lambda }_{A{l}^{3+}}^o+3{\Lambda }_{S{O}_4^{2-}}^o$
• B. ${\Lambda }_{A{l}^{3+}}^o+{\Lambda }_{S{O}_4^{2-}}^o$
• C. $({\Lambda }_{A{l}^{3+}}^o+{\Lambda }_{S{O}_4^{2-}}^o)\times 6$
• D. $\frac{1}{3}{\Lambda }_{A{l}^{3+}}^o+\frac{1}{2}{\Lambda }_{S{O}_4^{2-}}^o$

Answer 1

The correct option is B ${\Lambda }_{A{l}^{3+}}^o+{\Lambda }_{S{O}_4^{2-}}^o$

At infinite dilution, when dissociation is complete, each ion makes a definite contribution towards molar conductance of the electrolyte irrespective of the nature of the other ion with which it is associated.
Hence, ${\Lambda }_{A{l}_2(S{O}_4{)}_3}^o={\Lambda }_{A{l}^{3+}}^o+{\Lambda }_{S{O}_4^{2-}}^o$