Define specific, equivalent and molar conductance. Write their units. Derive the relation between specific conductance and molar conductance. What is the effect of dilution on specific and equivalent conductance?

Explanation

Specific conductance The reciprocal of specific resistance is known as specific conductance, i.e. the conductance of a solution of 1 cm length and having `1cm^(2)` area of cross-section. It is represented by `kappa`
`kappa=(1)/(R)xx(l)/(alpha)orkappa=Cxx(l)/(alpha)`
Here, C and R are conductance and resistance respectively.
Units of specific conductance are `Omega^(-1)cm^(-1)` or mho `cm^(-1)` or Siemens `m^(-1)` (in SI system).
Equivalent conductivity The conducting power of all the ions produced by dissolving 1g equivalent of an electrolyte in a given soluton is known as its equivalent conductivity. It is represented by `lambda_(eq)`.
Its units are `Omega^(-1)cm^(2)("equiv"^(-1))` or mho `cm^(2)("equiv"^(-1))` or S `cm^(2)("g-equiv"^(-1))`.
Molar conductivity The conducting power of all the ions produced by dissolving 1 g mole of an electrolyte of that solution. It is represented by `lambda_(m) or mu`. Molar conductance and specific conductance can be related as`lambda_(m) or mu=(kappaxx1000)/(M)`
where, M = concentration in mol/L, i.e. molarity of the solution. Its units are `Omega^(-1)cm^(2)mol^(-1)` or mho `cm^(2) mol^(-1) or S cm^(2) mol^(-1)`.
Effect of dilution on specific and equivalent conductance Conductivity always decreases with decrease in concentration (i.e. with dilution) for both strong and weak electrolytes. This is due to the fact that the number of ions that carry current in a unit volume of solution always decreases with decrease in concentration.