If the molar conductivity $\left(\Lambda_m\right)$ of a $0.050 \mathrm{~mol} \mathrm{~L}^{-1}$ solut

Question

If the molar conductivity $\left(\Lambda_m\right)$ of a $0.050 \mathrm{~mol} \mathrm{~L}^{-1}$ solution of a monobasic weak acid is $90 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}$, its extent (degree) of dissociation will be 
[Assume $\Lambda_{+}^{\circ}=349.6 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}$ and $\Lambda_{-}^{\circ}=50.4 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}$ ]

Professor PC Thomas Classes · Answer

(a) : Given : Concentration of solution $=0.050 \mathrm{~mol} \mathrm{~L}^{-1}$
$
\begin{aligned}
& \Lambda_m=90 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1} \
& \Lambda_m^{\mathrm{o}}=\Lambda_{+}^{\mathrm{o}}+\Lambda_{-}^{\mathrm{o}}
\end{aligned}
$
$\begin{aligned} & =349.6+50.4=400 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1} \ & \alpha=\frac{\Lambda_m}{\Lambda_m^{\circ}}=\frac{90}{400}=0.225\end{aligned}$