Editing Law of dilution (section)

==Limitations==

The Ostwald law of dilution provides a satisfactory description of the concentration dependence of the conductivity of weak electrolytes like CH<sub>3</sub>COOH and NH<sub>4</sub>OH.<ref>{{cite book |last=Laidler |first=Keith J. |date=1978 |title=Physical chemistry with biological applications |publisher=Benjamin/Cummings |page=266 |isbn=978-0-8053-5680-9 |author-link=Keith J. Laidler }}</ref> <ref>{{cite book |last1=Laidler |first1=Keith J. |last2=Meiser |first2=John H.|date=1982 |title=Physical chemistry |publisher=Benjamin/Cummings |page=260 |isbn=978-0-8053-5682-3 }}</ref> The variation of molar conductivity is essentially due to the incomplete dissociation of weak electrolytes into ions. 

For strong electrolytes, however, [[Gilbert N. Lewis|Lewis]] and [[Merle Randall|Randall]] recognized that the law fails badly since the supposed equilibrium constant is actually far from constant.<ref>{{cite journal |last1=Lewis |first1=Gilbert N. |last2=Randall |first2=Merle |title=The Activity Coefficient of Strong Electrolytes.1 |date=1921 |journal=Journal of the American Chemical Society |volume=43 |issue=5 |pages=1112–1154 |doi=10.1021/ja01438a014 |url=https://zenodo.org/record/2306457 }}</ref> This is because the dissociation of strong electrolytes into ions is essentially complete below a concentration threshold value. The decrease in molar conductivity as a function of concentration is actually due to attraction between ions of opposite charge as expressed in the [[Debye-Hückel-Onsager equation]] and later revisions.

Even for weak electrolytes the equation is not exact. [[Chemical thermodynamics]] shows that the true equilibrium constant is a ratio of [[thermodynamic activity|thermodynamic activities]], and that each concentration must be multiplied by an [[activity coefficient]]. This correction is important for ionic solutions due to the strong forces between ionic charges. An estimate of their values is given by the [[Debye–Hückel theory]] at low concentrations.