Question

The equivalent conductances of two strong electrolytes at infinite dilution in $H_{2}O$ (where ions move freely through a solution) at $25^{\circ }C$ are given below :
${\Lambda }_{C{H}_{3}COONa}^{\circ }=91.0Sc{m}^2/$ equivalent
${\Lambda }_{HCl}^{\circ }=426.2Sc{m}^2/$ equivalent.
What additional information/quantity one needs to calculate ${\Lambda }^{\circ }$ of an aqueous solution of acetic acid?

• A. ${\Lambda }^{\circ }$ of chloroacetic acid $ClC{H}_{2}COOH$
• B. ${\Lambda }^{\circ }$ of $NaCl$
• C. ${\Lambda }^{\circ }$ of $C{H}_{3}COOK$
• D. The limiting equivalent conductance of $H^{+}{\lambda }_{H^{+}}^0$

Answer 1

Answer: (B)

According to Kohlrausch's law, the molar conductivity at infinite dilution ${\Lambda }^{\circ }$ for weak electrolyte, $C{H}_{3}COOH$ is
${\Lambda }_{C{H}_{3}COOH}^{\circ }={\Lambda }_{C{H}_{3}COONa}^{\circ }+{\Lambda }_{HCl}^{\circ }-{\Lambda }_{NaCl}^{\circ }$
So, for calculating the value of ${\Lambda }_{C{H}_{3}COOH}^{\circ }$, value of ${\Lambda }_{NaCl}^{\circ }$ should also be known.