Q11 / 155 · WBJEE 2023 · Chemistry

The equivalent conductance of \(\mathrm{NaCl}, \mathrm{HCl}\) and \(\mathrm{CH}_3 \mathrm{COONa}\) at infinite dilution are \(126.45,426.16\) and 91 \(\mathrm{ohm}^{-1} \mathrm{~cm}^2 \mathrm{eq}^{-1}\) respectively at \(25^{\circ} \mathrm{C}\). The equivalent conductance of acetic acid (at infinite dilution) would be

  • A
    \(461.61 \mathrm{~ohm}^{-1} \mathrm{~cm}^2 \mathrm{~eq}^{-1}\)
  • Correct answer
    B
    \(390.71 \mathrm{~ohm}^{-1} \mathrm{~cm}^2 \mathrm{~eq}^{-1}\)
  • C
    cannot be determined from the given data
  • D
    \(208.71 \mathrm{~ohm}^{-1} \mathrm{~cm}^2 \mathrm{~eq}^{-1}\)

Solution

Hint : According to Kohlrausch's law \(\begin{aligned} & \wedge_{\mathrm{CH}_3 \mathrm{COOH}}^0=\wedge_{\mathrm{CH}_{3}\mathrm{COONa}}^0 +\wedge_{\mathrm{HCl}}^0-\wedge_{\mathrm{NaCl}}^0 \\ & \wedge_{\mathrm{CH}_3 \mathrm{COOH}}^0=(91+426.16-126.45) \mathrm{~ohm}^{-1} \mathrm{~cm}^2 \mathrm{~eq}^{-1} \\ & \wedge_{\mathrm{CH}_3 \mathrm{COOH}}^0=390.71 \mathrm{~ohm}^{-1} \mathrm{~cm}^2 \mathrm{~eq}^{-1} \end{aligned}\)

Hence, the correct answer is option: 'B'.

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