Significant and limitation of onsagar equation
Answers
Answer:
The Debye–Huckel theory was proposed by Peter Debye and Erich Hückel as a theoretical explanation for departures from ideality in solutions of electrolytes. further modified by Lars Onsager in 1927. All the postulates.
∙ The solute is completely dissociated; it is a strong electrolyte.
∙ Ions are spherical and are not polarized by the surrounding electric field. Solvation of ions is ignored except insofar as it determines the effective sizes of the ions.
∙ The solvent plays no role other than providing a medium of constant relative permittivity (dielectric constant).
∙ It was assumed that the electric field causes the charge cloud to be distorted away from spherical symmetry.
∙ There is no electrostriction.
∙ Individual ions surrounding a "central" ion can be represented by a statistically averaged cloud of continuous charge density, with a minimum distance of closest approach.
The last assumption means that each cation is surrounded by a spherically symmetric cloud of other ions. The cloud has a net negative charge. Similarly each anion is surrounded by a cloud with net positive charge.
After taking this into account, together with the specific requirements of moving ions, Onsager was able to derive a theoretical expression to account for the empirical relation known as Kohlrausch's Law, for the molar conductivity, Λm.
Λm=Λ0m−Kc√
Λ0m 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
Λm=Λ0m−(A+BΛ0m)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-Huckel-Onsager equation.
Explanation: