Question

The equivalent conductivity of N/10 solution of acetic acid at ${{25}^{0}}C$ is $14.3oh{{m}^{-1}}c{{m}^{2}}e{{q}^{-1}}$. Calculate the degree of dissociation of acetic acid if ${{\wedge }_{\infty }}C{{H}_{3}}COOH$ is 390.71.

Answer 1

Hint: “The degree of dissociation is the fraction of original solute molecules that have dissociated”. Degree of dissociation is usually indicated by the symbol $\alpha $. In detail, degree of dissociation refers to the amount of solute dissociated or ionized into ions or radicals per mole.

Complete Solution :
- Given that the equivalent conductivity of 0.1 N acetic acid solution at ${{25}^{0}}C~ is ~14.3 oh{{m}^{-1}}c{{m}^{2}}e{{q}^{-1}}$ .
- Given that the equivalent conductivity of acetic acid at infinite dilution is 390.71.
- Degree of dissociation is going to be denoted with the symbol $\alpha $.
\[\alpha =\dfrac{{{\wedge }_{v}}}{{{\wedge }_{\infty }}}\]
${{\wedge }_{v}}$ = equivalent conductance acetic acid at dilution v = $14.3oh{{m}^{-1}}c{{m}^{2}}e{{q}^{-1}}$ .
${{\wedge }_{\infty }}$= equivalent conductance of acetic acid at $\infty $ dilution of acetic acid = $390.71oh{{m}^{-1}}c{{m}^{2}}e{{q}^{-1}}$ .
\[\begin{align}
 & \alpha =\dfrac{{{\wedge }_{v}}}{{{\wedge }_{\infty }}} \\
 & = \dfrac{14.3}{390.71} \\
 & = 0.0366 \\
 & = 3.66\text{%}\!\!\!\!\text{ } \\
\end{align}\]
Degree of dissociation of Acetic acid at infinite dilution is 3.66%.

Note: Don’t be confused with the terms degree of dissociation, equivalent conductance, infinite dilution.
- Degree of dissociation: “The degree of dissociation is the concept of generating current carrying free ions, which are ionized from a fraction of solute at a given concentration”.
- Equivalent conductance: “The equivalent conductance of an electrolyte is defined as the conductance of a one equivalent weight of dissolved substance when placed between two similar electrodes at a distance of 1 cm”.
- Infinite dilution: “Infinite dilution is also defined as a solution which contains so much of solvent that when you add more solvent, there is no change in concentration of the solution”.