Question

The molar conductance of a $0.01M$ solution of acetic acid was found to be $16.30\times {10}^{-4}S{m}^{2}mo{l}^{-1}$ at ${25}^{\circ }C$. The molar ionic conductance of $H^{+}$ and $C{H}_{3}CO{O}^{-}$ ions at infinite dilution are $349.8\times {10}^{-4}$ and $40.9\times {10}^{-4}S{m}^{2}mo{l}^{-1}$, respectively, at the same temperature. What percentage of acetic acid is dissociated at this concentration?

Answer 1

$C{H}_{3}COOH⟶C{H}_{3}CO{O}^{-}+H^{+}$

Let ${\lambda }_{\infty }$denote molar conductance at infinite dilution.

${\lambda }_{\infty }\left(C{H}_{3}COOH\right)={\lambda }_{\infty }\left(C{H}_{3}CO{O}^{-}\right)+{\lambda }_{\infty }\left(H^{+}\right)$

$\therefore {\lambda }_{\infty }\left(C{H}_{3}COOH\right)=390.7\times {10}^{-4}S{m}^{2}mo{l}^{-1}$

$\%$ Dissociation $=\frac{molarConductanceof0.01MSolution}{molarconductanceatinfinitedilution}\times 100$

$=\frac{16.3\times {10}^{-4}}{390.7\times {10}^{-4}}\times 100=4.17\%$