2
$\begingroup$

For strong electrolytes, according to Kohlrausch, molar conductivity decreases as the concentration increases.

( i don't know why I'm not allowed to attach a photo here in order to show you the diagram ), but however I'm trying to explain how the diagram looks.

In the diagram we have strong electrolytes like $\ce{HCl,\, H2SO4,\, KCl,\, LaCl3,\, Na2SO4}$ whose molar conductivity decreases as the concentration increases. But, what I don't understand is that in the diagram we have also $\ce{CH3COOH}$ which is a weak electrolyte, and his molar conductivity also is decreasing and even far more rapidly, as the concentration increases.

Can somebody explain this ?

$\endgroup$
2
$\begingroup$

Kohlrausch in 1874 he demonstrated that an electrolyte has a definite and constant amount of electrical resistance. From 1875 to 1879, he examined numerous salt solutions, acids and solutions of other materials. This resulted in the law of the independent migration of ions, that is, each type of migrating ion has a specific electrical resistance no matter what its original molecular combination may have been.So this means that the electrical resistance of the ions in the solution that are migrating, and conductivity is just the inverse of this.

CH3COOH which is a weak electrolyte, so does not dissociate completely. Since it's only the migrating ions that affect it, only the dissociated ions affect conductivity and specific electrical resistance no matter what its original molecular combination may have been.

At lower concentrations, since there are more water molecules for every CH3COOH molecule, more of these dissociate so there are more migrating ions meaning a larger conductivity. The molar conductivity is defined as the solution conductivity normalized by the total ionic concentration. So concentration increases without any significant increase in conductivity meaning the molar conductivity decreases rapidly.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.