Question

Why does molar conductance increase with dilution?

Answer 1

Conductance is defined as the ease with which the electrons are moving in a solution. When one mole of electrolyte dissociates in a solution, then the amount of conductance is known as molar conductance of the solution. So, now we will see what actually molar conductance of a solution is and how it is calculated.

Complete answer:
Conductivity depends directly upon the number of ions present in the solution of electrolyte while the molar conductivity is defined as the conductivity due to the dissociation of one mole of electrolyte in the solution.
Molar conductance is dependent on the concentration of the solution.
Therefore, as we see, on dilution (adding more amount of water to the solution), the speed of the ions increases and for one mole the number of ions do not decrease.
So, as the velocity of ions increases in the solution, there is an increase in conductivity. And also, dilution results in the dissociation of more and more ions in the solution and hence there will be more active ions in the solution than before.
So, we can say that, on dilution, the number of active ions increases in the electrolytic solution as well as the velocity with which they are moving also increases. Hence, the molar conductance of an electrolytic solution increases with dilution.

Note:
We should not be confused between the terms molar conductivity and specific conductivity of a solution. Molar conductivity is defined as the conductivity due to the dissociation of one mole of electrolyte in the solution. Specific conductance is defined as the conductivity of an electrolytic solution with any certain concentration.