Law of dilution

Wilhelm Ostwald’s dilution law is a relationship proposed in 1888 between the dissociation constant K_d and the degree of dissociation α of a weak electrolyte. The law takes the form

${\displaystyle K_{d}={\cfrac {{\ce {[A+] [B^{-}]}}}{{\ce {[AB]}}}}={\frac {\alpha ^{2}}{1-\alpha }}\cdot c_{0}}$

Where the square brackets denote concentration, and c₀ is the total concentration of electrolyte.

Using ${\displaystyle \alpha =\Lambda _{c}/\Lambda _{0}}$, where ${\displaystyle \Lambda _{c}}$ is the molar conductivity at concentration c and ${\displaystyle \Lambda _{0}}$ is the limiting value of molar conductivity extrapolated to zero concentration or infinite dilution, this results in the following relation:

${\displaystyle K_{d}={\cfrac {\Lambda _{c}^{2}}{(\Lambda _{0}-\Lambda _{c})\Lambda _{0}}}\cdot c_{0}}$