3.7 Define conductivity and molar conductivity for the solution of an electrolyte.Discuss their variation with concentration.
Dear student
Conductivity (K):
It is the conductance of unit cube of material. S.I unit is S/m. Common unit is S/cm.
The conductivity of an electrolytic solution tend to decrease with decrease in concentration, that is, on dilution. The reason is with dilution, the frequency of dissociation increases and the total number of current-carrying ions increases but the number of ions per unit volume decreases.
Molar conductivity Λ:
It is the ratio of the electrolytic conductivity k to the molar concentration C of the dissolved electrolyte.
Λ=
C
k
It can also be defined as the conductance of a volume of solution containing 1 mole of dissolved electrolyte when kept between parallel electrodes 1 cm apart and large enough to contain between them all the solution.
The S.I unit of molar conductivity is Sm
2
/mol
The common unit of molar conductivity is Scm
2
/mol
The molar conductivity of strong and weak electrolytes tend to increase with dilution (i.e, decrease in the concentration). This is because with dilution, the frequency of dissociation increases and the total number of current-bearing ions increases.
Hope it helps
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