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Variation of conductivity with concentration
Concepts tested here
- Equivalent conductance of strong electrolytes
All Questions
2010 AIPMT-PRE 1 question
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An increase in equivalent conductance of a strong electrolyte with dilution is mainly due toA strong electrolyte is almost completely ionised at all concentrations, so dilution does not increase the number of ions.
In a concentrated solution the ions are close together and strong inter-ionic attractions slow them down.
On dilution the ions move farther apart, the inter-ionic attractions decrease and the ions move more freely, i.e., their mobility increases.
This is why the equivalent (molar) conductance of a strong electrolyte rises only slightly and linearly with $\sqrt{c}$ on dilution (Debye–Hückel–Onsager equation: $\Lambda_m = \Lambda_m^\circ - A\sqrt{c}$).
For a weak electrolyte, in contrast, the increase is mainly due to an increase in the number of ions.
Hence the increase is mainly due to an increase in the ionic mobility of ions.