Question

Define the following and write the formula and unit of each:
(A) Specific Conductivity.
(B) Molar Conductivity.

Answer 1

Hint : We know that equivalent conductance is defined as the conductance of all the ions produced by one-gram equivalent of an electrolyte in a given solution. In case, if the concentration of the solution is c gram equivalent per litre, then the volume containing $1$ g equivalent of the electrolyte will be $1000/e.$

Complete Step By Step Answer:
Specific Conductivity: It decreases with a decrease in concentration. As the number of ions per unit volume that carry current in a solution decreases on dilution. Thus, concentration and conductivity are directly proportional to each other. Specific Conductance is the conductance of a given solution enclosed in a cell having two electrodes which are of unit area and are separated by $1cm.$
Formula - $\kappa = \dfrac{1}{\rho} = \dfrac{1}{A} \times \dfrac{l}{R}$
Where, $\rho = \;specific\;resistance$
$l = \;length$
$A = \;Area$
$R= \;Resistance$
Unit - $Ohm^{-1}\;cm^{-1}$

Molar conductivity: It is the conductance property of a solution containing one mole of the electrolyte or it is a function of the ionic strength of a solution or the concentration of salt. It is therefore not a constant. In other words, molar conductivity can also be defined as the conducting power of all the ions that are formed by dissolving a mole of electrolyte in a solution. Molar conductivity is the property of an electrolyte solution that is mainly used in determining the efficiency of a given electrolyte in conducting electricity in a solution. It is therefore not a constant.
Formula - $\mu = \kappa \times V$
$\mu = \kappa \times \dfrac{1000}{m}$
Where, $\mu = \;molar\;conductivity$
$\kappa = \;specific\;conductivity$
$m = \;molarity$
$V= \;volume$
Unit - $Ohm^{-1}\;cm^{2}\;mol^{-1}$

Note :
Remember that we should also know the effect of concentration on molar conductivity. The molar conductivity of both weak and strong electrolytes increases with a decrease in concentration or dilution. We know that the molar conductivity is the conductivity offered by one mole of ions.