Effect of concentration on molar conductivity of electrolytes

The molar conductivity of electrolytes is influenced by the concentration of the solution. Here are some key points to understand the effect of concentration on molar conductivity:

1. Generally, the molar conductivity of an electrolyte decreases as the concentration increases.
2. This behavior is explained by the phenomenon of ion-ion interactions or the association of ions when the concentration increases.
3. Initially, at low concentrations, the ions are far apart from each other, resulting in minimal ion-ion interactions. This allows for higher mobility of the ions and a higher molar conductivity.
4. As the concentration increases, the ions come closer to each other, leading to a greater likelihood of ion-ion interactions or association. This hinders the mobility of the ions, reducing the molar conductivity.
5. At higher concentrations, the molar conductivity approaches a limiting value called the limiting molar conductivity (Λ°). This value represents the maximum molar conductivity attainable for the electrolyte under the given conditions.
6. The decrease in molar conductivity with increasing concentration can be described by Kohlrausch's law, which states that the molar conductivity of an electrolyte is the sum of the contributions of the individual ions in the solution.
7. In dilute solutions, where ion-ion interactions are minimal, the molar conductivity is mainly determined by the individual ion mobilities. As the concentration increases, the contributions from individual ion mobilities decrease due to increased ion-ion interactions.
8. Strong electrolytes, which undergo complete ionization in solution, show a more pronounced decrease in molar conductivity with increasing concentration compared to weak electrolytes.

In summary, as the concentration of an electrolyte increases, the molar conductivity tends to decrease due to increased ion-ion interactions or association. However, at very low concentrations, the molar conductivity is higher, indicating greater ion mobility.