The equivalent conductance order is $\ce{Br-} > \ce{Cl-} > \ce{F-}$.

$$Λ = \frac{κ}{c},$$

so $Λ$ is proportional to specific conductance?

But in ion chromatography we get peak area where $\ce{F-} > \ce{Cl-} > \ce{Br-}$ (specific conductance, μS/cm) for the same concentration, let us say 1 ppm.


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    $\begingroup$ Are they of the same concentration? As without that knowledge, the order of the conductivity ( specific conductance ) is undefined. $\endgroup$ – Poutnik Jun 2 '19 at 6:43
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    $\begingroup$ yes sir. lets say 1ppm $\endgroup$ – ggs Jun 2 '19 at 7:25

ppm is ambiguous quantity, it can be v/v, w/v,w/w,n/n.

By other words, all 1 ppm very probably is not the same molar concentration, unless it is n/n ppm, relating itself to the molar amount of the solution.

$\Lambda = \kappa /c$ is correct, but $c$ must be the molar concentration.

$$\Lambda[\pu{Sm^2mol^-1}]=\frac{M[\pu{g/mol}]}{c[\pu{ppm as g/m^3}]}\cdot \kappa[\pu{S/m}]$$

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  • $\begingroup$ Thank u sir. I missed the conc. unit. $\endgroup$ – ggs Jun 2 '19 at 9:01
  • $\begingroup$ @ggs Please don't post a "thank you" as a comment. Instead, upvote and/or accept answers that were useful to you. $\endgroup$ – andselisk Jun 2 '19 at 19:21

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