Molar Conductivity Calculator
Λm = κ/c, plus the degree of dissociation.
Work out Molar Conductivity. Λm = κ/c, plus the degree of dissociation. Shows the working, not just the answer.
Keep the units consistent with the conductivity — the ratio is what matters.
Optional. At infinite dilution, from tables. Gives the degree of dissociation.
Molar conductivity Λm
10
79.4% dissociated — weak electrolyte
Molar conductivity is conductivity divided by concentration, which removes the trivial effect of simply having more ions and leaves how well each mole actually conducts. It rises as a solution is diluted, for two different reasons depending on the electrolyte. A strong electrolyte is already fully dissociated, so the rise is only ions getting out of each other's way — Kohlrausch's square-root law. A weak electrolyte dissociates further as it dilutes, so its molar conductivity climbs steeply and the ratio to the limiting value gives the degree of dissociation directly. That ratio is how Ostwald's dilution law is used to measure Ka for a weak acid without ever measuring a pH.
How the Molar Conductivity Calculator works
Enter a measured conductivity and concentration to get molar conductivity, and add a limiting value to get the degree of dissociation. That ratio is how Ka for a weak acid can be measured by conductivity alone, without ever taking a pH reading.
Also known as: conductivity to molar conductivity · degree of dissociation calculator · kohlrausch law calculator · limiting molar conductivity
Frequently asked questions
What is molar conductivity?
Conductivity divided by concentration, Λm = κ/c. Dividing out the concentration removes the trivial effect of simply having more ions present and leaves how well each mole actually conducts.
Why does molar conductivity rise on dilution?
For two different reasons. A strong electrolyte is already fully dissociated, so the rise is only ions getting out of each other's way. A weak electrolyte dissociates further as it dilutes, so its molar conductivity climbs much more steeply.
What is the degree of dissociation?
α = Λm/Λ°m — the measured molar conductivity divided by the value at infinite dilution. For a weak electrolyte it is the fraction actually ionised; for a strong one it is close to 1.
What is Kohlrausch's law?
That limiting molar conductivity is the sum of independent ionic contributions. It lets Λ° be worked out for a weak acid, which cannot be measured directly, from strong electrolytes that can.
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