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Explain debey huckel onsagers law of the strong electrolytes

Explain debey huckel onsagers law of the strong electrolytes

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Aarti Gupta
askIITians Faculty 300 Points
10 years ago
Debye–Hückel limiting law that describes the behavior of strong electrolytes. In explaining the non-ideal behavior of strong electrolytes, his mathematical treatment assumes that each ion is surrounded by an ionic cloud of oppositely charged ions, which retards the movement of ions in the medium. The theory not only provides a method for calculation of activity coefficients, but has also helped, among other things, in our understanding of diffusion in ionic media, change in the rate of ionic reactions upon addition of salts, and biochemical reactions.
Debye and Hückel modified their theory in 1926 and their theory was further modified by Onsager. All the postulates of the original theory were retained. In addition it was assumed that the electric field causes the charge cloud to be distorted away from spherical symmetry. After taking this into account, together with the specific requirements of moving ions, such as viscosity and electrophoretic effects, Onsager was able to derive a theoretical expression to account for the empirical relation known as Kohlraush's law for the molar conductivity, ?m.
\Lambda_m =\Lambda_m^0-K\sqrt{c}

\Lambda_m^0 is known as the limiting molar conductivity, K is an empirical constant and c is the electrolyte concentration Limiting here means "at the limit of the infinite dilution"). Onsager's expression is

\Lambda_m =\Lambda_m^0-(A+B\Lambda_m^0 )\sqrt{c}

where A and B are constants that depend only on known quantities such as temperature, the charges on the ions and the dielectric constant and viscosity of the solvent. This is known as the Debye-Hückel-Onsager equation. However, this equation only applies to very dilute solutions.

Thanks & Regard

Aarti Gupta

askiitians Faculty

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