Huckel-Onsager equation

The Debye-Huckel-Onsager equation for the dependence of the ordinary diffusion conductance on concentration has been extended by Falkenhagen, Leist and Kelbg [3] to apply to more concentrated solutions and their equation for a 1 1-electrolyte may be written... 

Debye-Huckel-Onsager equation Onsager equation, - Debye-Huckel-Onsager theory... 

Theoretical Predictions of the Debye-Huckel-Onsager Equation versus the Observed Conductance Curves... 

The Debye-Huckel-Onsager equation has been tested against a large body of accurate experimental data. A comparison of theory and experiment is shown in Fig. 4.93 and Table 4.21 for aqueous solutions of true eiectroiytes, i.e., substances that consisted of ions in their crystal lattices before they were dissolved in water. At very low concentrations (< 0.(X)3 N), the agreement between theory and experiment is very good. There is no doubt that the theoretical equation is a satisfactory expression for the limiting tangent to the experimentaiiy obtained/ versus curves. 

Validity of the Debye-Huckel-Onsager Equation.—For a uni-univalent electrolyte, the Onsager equation (36), assuming complete dissociation, may be written in the form... 

The first conclusion regarding figures 4.26 and 27 is that for xa /(xa) approaches 1.5 (fig. 4.26) whereas for xa -4 0 /(xa) -4 1.0 (fig. 4.27). In other words, in the appropriate limits the Helmholtz-Smoluchowski [4.3.4) and Huckel-Onsager equations (4.3.5) are retrieved. So it is concluded that these two limiting laws also remain valid when the double layer is polarized. This is an extension of Morrison s result, quoted in connection with 14.3.20). 

II) For very low xa the Huckel-Onsager equation (4.3.5] is valid. Example particles in media of low polarity. The applicability limit can be deduced from fig. 4.27. 

A simple treatment of the derivation of the Debye-Huckel-Onsager equation 1927 for symmetrical electrolytes... 

Use of the Debye-Huckel-Onsager equation for symmetrical strong electrolytes which are fully dissociated... 

From this it can be seen that the correct form of the Debye-Huckel-Onsager equation to be used to compare with the experimental results is one in which stoichiometric concentrations appear. 

For very dilute solutions, the equivalent conductivity for any electrolyte of concentration c can be approximately calculated using the Debye-Huckel-Onsager equation, which can be written for a symmetrical (equal charge on cation and anion) electrolyte as... 

Fig. 3.5. Comparison of equivalent conductance. A, of various electrolytes as predicted by Debye-Huckel-Onsager equation (3.30) with those observed experimentally. [Adapted from J. O M. Bockris and A. K. N. Reddy, Modern Electrochemistry (New York Plenum Press, 1970), Vol. 1, p. 436.]...

See also -> Debye-Clausius-Mossotti equation, -r Debye-Huckel-Onsager equation, -> dielectric relaxation. 

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