Question -
Answer -
Conductivity of a solution isdefined as the conductance of a solution of 1 cm in length and area ofcross-section 1 sq. cm. The inverse of resistivity is called conductivity orspecific conductance. It is represented by the symbol╬║. If ╧Б isresistivity, then we can write:
The conductivity of a solution atany given concentration is the conductance (G) of one unit volume ofsolution kept between two platinum electrodes with the unit area ofcross-section and at a distance of unit length.
i.e.,┬а
(Since┬аa┬а=1,┬аl┬а= 1)
Conductivity always decreaseswith a decrease in concentration, both for weak and strong electrolytes. Thisis because the number of ions per unit volume that carry the current in asolution decreases with a decrease in concentration.
Molar conductivity:
Molarconductivity of a solution at a given concentration is the conductance ofvolume V of a solution containing 1 mole of the electrolyte kept between twoelectrodes with the area of cross-section┬аA┬аand distance ofunit length.
Now,┬аl┬а= 1and┬аA┬а= V (volume containing 1 mole of the electrolyte).
Molar conductivity increases witha decrease in concentration. This is because the total volume V of the solutioncontaining one mole of the electrolyte increases on dilution.
Thevariation of┬а
with
for strong and weak electrolytes is shown in thefollowing plot:
┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а ┬а