Chemistry - Electrochemistry Question with Solution | TestHub

According to the Debye-Huckel-Onsager equation for strong electrolytes:

${\Lambda }_m={\Lambda }_m^0-A\sqrt{c}$

The slope of the plot of ${\Lambda }_m$ versus $\sqrt{c}$ is $-A$.

Given slope $=-90.0$, we have $A=90.0$.

At $c=0.01$ M, $\sqrt{c}=0.1$ M${}^{1/2}$.

Substituting the given values into the equation:

$145.0={\Lambda }_m^0-90.0\times 0.1$

$145.0={\Lambda }_m^0-9.0$

${\Lambda }_m^0=154.0$ S cm${}^2$ mol${}^{-1}$

According to Kohlrausch's law of independent migration of ions:

${\Lambda }_m^0(\text{XY})={\lambda }_{{\text{X}}^{+}}^0+{\lambda }_{{\text{Y}}^{-}}^0$

$154.0=74.0+{\lambda }_{{\text{Y}}^{-}}^0$

${\lambda }_{{\text{Y}}^{-}}^0=154.0-74.0=80.0$ S cm${}^2$ mol${}^{-1}$

Answer: $80.0$