Assertion (A) : Conductivity of an electrolyte increases with decrease in concentration.Reason (R) : Number of ions per unit volume decreases on dilution

The assertion (A) is incorrect while the reason (R) is correct.

Here's why:

(A) The conductivity of an electrolyte actually decreases with a decrease in concentration. This is because conductivity is directly proportional to the concentration of ions in the solution. When the concentration decreases, the number of ions available to carry the charge also decreases, leading to a decrease in conductivity.

(R) The reason is correct. When an electrolyte is diluted, the number of ions per unit volume decreases. This is because dilution involves adding more solvent to the solution, which increases the volume of the solution but does not increase the number of ions. As a result, the concentration of ions (number of ions per unit volume) decreases.