Question

Which one of the following statements is correct for an electrolyte solution when its concentration is decreased?
A. Both specific and molar conductances decrease
B. Both specific and molar conductances increase
C. Specific conductance increase and molar conductance decreases
D. Specific conductance decreases and molar conductance increases

Answer 1

An electrolyte solution is a solution consisting of positively and negatively charged ions which conduct electric current by migration of ions to negative and positive terminals.

Complete step by step answer:
Specific conductance is the ability of an electrolyte to conduct electric current. It is expressed as Siemens per meter. Molar conductance is the ratio of conductance and the molar concentration of the electrolyte.
Both specific conductivity and molar conductivity of an electrolyte varies with the change in concentration of the electrolyte. In general for weak and strong electrolytes conductivity always decreases with decrease in concentration. The reason is on dilution the number of ions decreases per unit volume that carries the current in a solution due to larger separation of ions in the solution.
As molar conductivity is inversely proportional to conductance so the molar conductivity increases with decrease in concentration. This is accounted for by the change in total volume of a solution. The volume of the solution increases on dilution, which results in decrease in specific conductance and thereby increase in molar conductance.
Thus the correct option is D, i.e. specific conductance decreases and molar conductance increases.

Note:
Specific conductivity depends on nature and concentration of electrolyte, solvent nature and viscosity, size of ions and temperature. Molar conductivity depends on concentration in moles per volume and specific conductance.