Variation of molar conductivity on dilution:

In the case of weak electrolytes (for example CH₃COOH, ammonia, organic fatty acids, etc), the ionization will increase with dilution, and hence, the molar conductivity increases with dilution. Therefore the conductivity is directly proportional to the degree of dissociation of a weak electrolyte. These above results are depicted in Figure in which the molar conductivity, Λm, of two electrolytes (KCl and acetic acid) at a constant temperature is plotted against √c. It may be seen from the figure that two different types of behaviours are exhibited by these electrolytes. The strong electrolyte, KCl shows a linear plot (almost straight lines). Instead, the weak electrolyte, CH₃COOH seems to approach the dilute solution limit almost tangentially. It is, however, impossible to draw a sharp line of demarcation between the two categories as many substances are known to exhibit intermediate behaviour, example for nickel sulphate. Like electrolytes are sometimes called moderately strong electrolytes.

Figure: Variation of molar conductivity on dilution (a) for aqueous solution of potassium chloride (strong electrolyte) (b) acetic acid (weak electrolyte)