Question

What is the effect of dilution on specific, molar, equivalent conductance?

Answer 1

Effect of dilution are as follows:
(i) The conductivity of solution increases on dilution.
(ii) The specific conductivity decreases on dilution (as the number of ions decreases w.r.t. to volume).
(iii) The equivalent and molar conductivities increase with dilution.
(iv) The equivalent and molar conductivities tend to acquire maximum value with increasing dilution. [Maximum at dilution]
(v) Variation of molar conductance with concentration: for a strong electrolyte it is shown by Debye-Huckel Sagar equation as follows:
In place of we can also use
${\Lambda }_m={\Lambda }_m^{-}-b\sqrt{c}{\Lambda }^0{\Lambda }^{\infty }$
Here, = molar conductance at infinite.
${\Lambda }_M^0$
dilution (Limiting molar conductance)
= Molar conductance at V-dilution
${\Lambda }_m$
b = It is a constant which depends upon nature of solvent and temperature
c = concentration


At higher concentration, these attractions are stronger so fewer deviations are observed in the value of with dilution.
$\Lambda M$
In case of weak electrolytes, increase in dissociation takes place on dilution. In case of strong electrolyte, it can be observed by extrapolating concentration to zero. However, in case of weak electrolytes, it is possible.
$\Lambda M{\Lambda }^{\infty }$
Determination of cell constant
In order to find out the cell constant, the cell is filled with 0.1N solution of chemically pure KC1. The specific conductivity of 0.1 N KCI solution as determined accurately by Kohlraush is at and the resistance of the solution is determined experimentally. Substituting the value of specific conductivity (0.002765) and offered by potassium chloride solution, the value of cell constant, x is calculated as follows:
$0.002765\mho c{m}^{-1}{25}^{0}C$
$\because SpecificConductivity=\frac{Cellconstant,x}{Resistance}$
$\therefore Cellconstant,x=Sp.Conductivity\times resistance\left[3mm\right]orx=0.002765\times resistance$