# What should be the order of specific conductance (κ) of floride, chloride and bromide ions?

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.

Why?

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

## 1 Answer

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.

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

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