Question

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

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

Answer 1

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

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