The molar conductivities of $\mathrm{KCl}, \mathrm{NaCl}$ and $\mathrm{KNO}_3$ are 100,120 and $90…

The molar conductivities of $\mathrm{KCl}, \mathrm{NaCl}$ and $\mathrm{KNO}_3$ are 100,120 and $90 \mathrm{~cm}^2 \mathrm{~mol}^{-1}$, respectively. The molar conductivity of $\mathrm{NaNO}_3$ would be .......... cm $\mathrm{mol}^{-1}$.
  1. 110
  2. 290
  3. 310
  4. 120

Solution

\(\underset{120}{\mathrm{NaCl}}+\underset{90}{\mathrm{KNO}_3} \longrightarrow \mathrm{NaNO}_3+\underset{100}{\mathrm{KCl}}\)
molar conductivity $\Lambda_{\mathrm{m}}^{\circ}$ According to Kohlrausch law,
\(\begin{aligned} \Lambda_{\mathrm{m}}^{\circ}\left(\mathrm{NaNO}_3ight) & =\Lambda_{\mathrm{m}}^{\circ}(\mathrm{NaCl})+\Lambda_{\mathrm{m}}^{\circ}\left(\mathrm{KNO}_3ight)-\Lambda_{\mathrm{m}}^{\circ}(\mathrm{KCl}) \\ & =120+90-100=110 \mathrm{~cm}^2 \mathrm{~mol}^{-1}\end{aligned}\) .

Asked in: JEE-TOPICTESTS-CHEMISTRY

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