Question

The one which decreases with dilution is
(A) Molar Conductivity
(B) Conductance
(C) Specific conductivity
(D) None of the above

Answer 1

The Conductivity of an electrolyte in a solution depends upon various factors like the number of ions, concentration, temperature, nature of the electrolyte. Molar conductivity, conductance, and specific conductivity all of the three terms depend on these factors.

Complete step by step answer:
Molar conductivity is the total conducting power of ions present in $1$ mole of electrolyte when it is dissolved in water. It is denoted by ${\lambda _m}$.
The molar conductivity of an electrolyte increases when the concentration is decreased. This is due to the reason that the total volume, $V$, of the solution containing $1$ mole of electrolyte also increases. When dilution happens, the concentration decreases. Also, when the concentration reaches zero, the molar conductivity of the solution is known as limiting molar conductivity. Hence, with dilution, the molar conductivity of a strong electrolyte increases.
The specific conductivity of an electrolytic solution at a given concentration is defined as the conductance of the ions present in the unit volume of the solution. It is the conductance of volume $V$ of the solution that has one mole of electrolyte which is kept between two electrodes whose area of cross-section is $A$ and the distance is $1\,cm$.
The conductivity of a solution is because of the movement of ions present in the solution. Pure water is not very conductive, but saltwater is very conductive because the more ions dissolved in solution, the higher will be the conductivity (up to a limit). Upon dilute, the concentration of ions decreases, and so does the ability to pass current. Therefore, the specific conductance decreases on dilution.

Hence, Option (C) is correct.

Note:
The conductivity or specific conductance of an electrolytic solution is the measure of its ability to conduct electricity. Its SI unit is Siemens per meter. Specific conductivity depends upon the size of ions, temperature, and nature of the electrolyte.