Question

Define the terms conductivity and molar conductivity for the solution of an electrolyte. Comment on their variation with temperature.

Answer 1

Both terms conductivity and molar conductivity relate the conductance of solution to the amount of electrolyte. The amount of electrolyte can be expressed either in terms of volume of in terms of number of moles.

Complete step by step answer:
Consider a solution placed in a container of length one centimeter and cross section area of one square centimeter. The container is completely filled with the solution. The conductance of this solution is called the conductivity. In other words, wecan define the conductivity as the conductance of a solution having length of one centimeter and cross section area of one square centimeter.
When we increase the temperature, we increase the interaction of ions. So we also increase the conductivity of the solution. Thus, the conductivity of the solution increases with increase in temperature.
Consider that we dissolve one mole of an electrolyte in the solution and measure the conducting power of all the ions produced. This conducting power is equal to the molar conductivity. Thus, wecan define the molar conductivity as the conducting power of all the ions obtained when one mole of an electrolyte is dissolved in the solution.
When we increase the temperature, we increase the interaction of ions. So we also increase the molar conductivity of the solution. Thus, the molar conductivity of the solution increases with increase in temperature.

Note: The volume of a cube having length of one centimeter and cross section area of one square centimeter is equal to one cubic centimeter. Thus, the conductivity of solution is the conductance of one cubic centimeter of the solution. Similar to molar conductivity, there is another concept called equivalent conductivity. It is equal to the conducting power of one gram equivalent of the electrolyte.