Question

What is the unit of molar conductivity?

Answer 1

Hint: You should recall the definition of molar conductance, from there you can easily write the formula and then the unit. So, Molar conductance is defined as the conducting power of all the ions produced by dissolving one mole of an electrolyte in solution. Now you can easily answer this question.

Complete step by step answer:
First, we should know about 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.
The following expression is used to mathematically represent molar conductivity.
$\Lambda _{ m }$ = k / C
Where k is the specific conductivity and c is the concentration in mole per liter.
Specific conductivity (better known as conductivity) is the measure of the ability of that material to conduct electricity. It is represented by the symbol “k”.
$k\quad =\quad { 1 }/{ \rho }$
${ \rho }$ = resistivity, it has the unit m/S
Here, the unit of k is S/m and unit of C is mol/L
The SI unit of molar conductivity is Siemens metre-squared per mole ($Sm^{ 2 }mol^{ -1 }$). However, values are often quoted in S cm2 mol−1.
Therefore, we can say that the unit of molar conductance is $Sm^{ 2 }mol^{ -1 }$.

Note: 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. Even after dilution, we are still considering the same unit mole of ions. But however, the increased dilution results in the dissociation of more electrolytes into ions and effectively increasing the number of active ions in the solution.
These active ions impart more conductivity.