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Define conductivity and molar conductivity for the solution of an electrolyte . Discuss their variation with concentration.

3.7   Define conductivity and molar conductivity for the solution of an electrolyte. Discuss their variation with concentration.

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Conductivity(k) or specific conductance of a solution is defined as the inverse of resistivity.

Mathematically, it can be written as:-

$G = \kappa \frac{A}{L}$

In the above equation is$\kappa$ the conductivity of a solution. Thus the definition of conductivity becomes as the conductance of a substance which is 1 cm long and has 1 sq. cm of cross-sectional area.

With dilution conductivity of a solution decreases due to an increase in distance between ions.\

Molar conductivity:-  It is defined as the conductivity of a solution per unit concentration

i.e.,                                       $\Lambda _M\ =\ \frac{\kappa }{C}$

It is clear from the above mathematical expression of the molar conductivity that, if we dilute the solution or decrease its concentration then molar conductivity increases. This is because, on dilution of a solution, a decrease in is$\kappa$ more than compensated by the increase in its volume.

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