Question

What is limiting molar conductivity of acetic acid?

Answer 1

Hint: The conductivity of an electrolyte depends upon the dissociation of its consecutive in the solution. If the concentration of solution is large then the dissociation becomes less. At infinite dilution of solution the dissociation of ions is greatest, at that stage the conductivity of solution is called limiting molar conductivity . We have to use Kohlrausch's Theorem for finding the limiting molar conductivity.

Complete answer:
The dissociation of any ions depends upon the concentration of the solution in which it has to be dissociated. If the concentration of solution is high then it is hard to dissociate further. But if the solution is diluted then the further dissociation of ions takes place easily. Thus the conductivity of solution at particular concentration is called its molar conductivity. But at infinite dilution the conductivity of the electrolyte is called limiting molar conductivity .
According to Kohlrauch Law , the limiting molar conductivity of an electrolyte can be represented as the sum of individual anion and cation of electrolyte .It is denoted by ${\lambda ^ \circ }_m$. Acetic acid is weak acid and hence it is dissociated into :
$C{H_3}COOH{\text{ }}\xrightarrow{{}}{\text{ C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - }{\text{ + }}{{\text{H}}^ + }$
Thus its limiting molar conductivity can be represented as the sum of its anion and cation.
Therefore,
${\lambda _m}^ \circ (C{H_3}COOH){\text{ = }}{\lambda _m}^ \circ (C{H_3}CO{O^ - }){\text{ + }}{\lambda _m}^ \circ ({H^ + })$

Note:
Thus limiting molar conductivity can be calculated for weak as well as for strong acid or base too. The only condition is that the electrolyte must be diluted at infinity. Also we can perform algebraic operations on the above equation too. The unit of limiting molar conductivity is$S{\text{ }}{m^{ - 1}}$. The limiting molar conductivity is maximum conductivity of an electrolyte.