Question

The ionization constant of a weak electrolyte $\left(HA\right)$ is $25\times {10}^{-6}$, while the equivalent conductance of its $0.01\text{M}$ solution is $19.6\text{Scm}2{\text{eq}}^{-1}$. The equivalent conductance of the electrolyte at infinite dilution (in ${\text{S cm}}^2{\text{eq}}^{-1}$) will be:

• A. $250$
• B. $196$
• C. $392$
• D. $384$

Answer 1

The correct option is C $392$

Given,
$\text{Ionization constant}{K}_a=25\times {10}^{-6}$
$\text{Equivalent conductance}{\Lambda }_{\text{eq}}=19.6\text{Scm}2{\text{eq}}^{-1}$
$\text{Concentration (C)}=0.01\text{M}$
Here, $K_a=C{\alpha }^2$
$25\times {10}^{-6}=0.01\times {\alpha }^2$
$\Rightarrow \alpha =5\times {10}^{-2}$
Therefore, the equivalent conductance of the electrolyte at infinite dilution ${\Lambda }_{eq}^o=\frac{{\Lambda }_{\text{eq}}}{\alpha }=\frac{19.6}{5\times {10}^{-2}}=392{\text{Scm}}^2{\text{eq}}^{-1}$