Theory of Electrolytes

The distinction between these two types of electrolytes is not sharply defined because electrolytes with a medium degree of dissociation are known (e. g. aqueous solutions of cyanoacetic acid, o-ch lor benzoic acid, o-nitrobenzoic acid, 3—5 di-nitrobcnzoic acid etc .). As the number of such electrolytes is comparatively small, no special account will be taken of them. Analogically all nonaqueous solutions can be omitted as in technical electrochemistry water is exclusively used in the preparation of solutions of electrolytes. 

These phenomena that were previously considered anomalies of the mentioned colligative properties of the solutions, have been dealt with by Arrhenius in his effort to explain such anomalies by his well known theory of electrolytic dissociation. According to this explanation the molecules of a dissolved electrolyte partly split to form smaller particles, i. e. ions, which from the thermodynamic point of view are as effective as the undissociated molecules themselves. As the number of particles of matter is thus greater, the manifestations of colligative properties are increased, compared to what they would be with an undissociated electrolyte. 

According to the Arrhenius conception electrolytes dissociate in solutions to a certain degree that depends solely on the concentration at a given temperature. The dissociation is partial at finite concentration but it increases with increasing dilution and it becomes complete at infinite dilution. At a given temperature 

The theory of Arrhenius has proved its value with some minor supplements in explaining the behaviour of weak electrolytes, it failed, however, completely when applied to strong electrolytes. Success in the case of weak electrolytes can be explained by the fact that because of the comparatively small number of ions and because of the considerable distances between them, there is no substantial difference between ions and undissociated molecules as far as their individual behaviour is concerned. We may, therefore, assume that all these particles regardless of their nature play an equal part in the determination of the thermodynamic properties of the solution. The degree of dissociation has in this case a concrete meaning and individual weak electrolytes can be differentiated by their characteristic dissociation constants. 

Unlike weak electrolytes, solutions of strong ones have a far higher specific conductance the rise of the latter with rising concentration is also much more rapid. There is another difference the anomalies ascertained in the colligative properties of strong electrolytes cannot be ascribed to partial dissociation of molecules to ions as in the case of weak electrolytes. 

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Going beyond die limiting law it is found that the modified (or renonnalized) virial coefficients in Mayer s theory of electrolytes are fiinctions of the concentration through their dependence on k. The ionic second virial coefficient is given by [62]... 

Outhwaite C W 1974 Equilibrium theories of electrolyte solutions Specialist Periodical Report (London Chemical Society)... 

Rasaiah J C 1987 Theories of electrolyte solutions The Liquid State and its Electrical Properties (NATO Advanced Science Institute Series Vol 193) ed E E Kunhardt, L G Christophous and L H Luessen (New York Plenum)... 

Huckel was a German physi cal chemist Before his theo retical studies of aromaticity Huckel collaborated with Peter Debye in developing what remains the most widely accepted theory of electrolyte solutions... 

The Dehye-Hbckel theory of electrolytes based on the electric field surrounding each ion forms the basis for modern concepts of electrolyte behavior (16,17). The two components of the theory are the relaxation and the electrophoretic effect. Each ion has an ion atmosphere of equal opposite charge surrounding it. During movement the ion may not be exacdy in the center of its ion atmosphere, thereby producing a retarding electrical force on the ion. 

The importance of this advance is hidden in the simple words It is shown... , and furthermore in the parallel drawn with the D-H theory of electrolytes. This was... 

Amplitude of a process, 114. Andrew s diagram, 173 Anisotropic bodies, 193 Aphorism of Clausius, 83, 92 Arrhenius theory of electrolytic dissociation, 301 Aschistic process, 31, 36, 51 Atmosphere, 39 Atomic energy, 26 Availability, 65, 66 Available energy, 66, 77, 80, 98, 101... 

Falkenhagen, H. The Present State of the Theory of Electrolytic Solutions 2... 

Further simphfication of the SPM and RPM is to assume the ions are point charges with no hard-core correlations, i.e., du = 0. This is called the Debye-Huckel (DH) level of treatment, and an early Nobel prize was awarded to the theory of electrolytes in the infinite-dilution limit [31]. This model can capture the long-range electrostatic interactions and is expected to be valid only for dilute solutions. An analytical solution is available by solving the Pois-son-Boltzmann (PB) equation for the distribution of ions (charges). The PB equation is... 

The first substantial constitutive concept of acid and bases came only in 1887 when Arrhenius applied the theory of electrolytic dissociation to acids and bases. An acid was defined as a substance that dissociated to hydrogen ions and anions in water (Day Selbin, 1969). For the first time, a base was defined in terms other than that of an antiacid and was regarded as a substance that dissociated in water into hydroxyl ions and cations. The reaction between an acid and a base was simply the combination of hydrogen and hydroxyl ions to form water. 

Aqueous electrolyte solutions have been a subject of determined studies for over a century. Numerous attempts were made to construct theories that could link the general properties of solutions to their internal structure and predict properties as yet nnknown. Modem theories of electrolyte solutions are most intimately related to many branches of physics and chemistry. The electrochemistry of electrolyte solutions is a large branch of electrochemistry sometimes regarded as an independent science. 

Thus, quantitative criteria that could be tested experimentally had now been formulated for the first time in the theory of electrolytic dissociation, in contrast to earlier theories. The good agreement between degrees of dissociation calculated from independent measurements of two different properties with Eqs. (7.5) and... 

Soon after inception of the theory of electrolytic dissociation, it was shown that two types of componnds exist that can dissociate upon dissolution in water (or other solvents) ... 

The theory of electrolytic dissociation also provided the possibility for a transparent definition of the concept of acids and bases. According to the concepts of Arrhenius, an acid is a substance which upon dissociation forms hydrogen ions, and a base is a substance that forms hydroxyl ions. Later, these concepts were extended. 

The theory of electrolytic dissociation was not immediately recognized universally, despite the fact that it could qualitatively and quantitatively explain certain fundamental properties of electrolyte solutions. For many scientists the reasons for spontaneous dissociation of stable compounds were obscure. Thus, an energy of about 770kJ/mol is required to break up the bonds in the lattice of NaCl, and about 430kJ/mol is required to split H l bonds during the formation of hydrochloric acid solution. Yet the energy of thermal motions in these compounds is not above lOkJ/mol. It was the weak point of Arrhenius s theory that this mismatch could not be explained. 

Between 1865 and 1887, Dmitri 1. Mendeleev developed the chemical theory of solutions. According to this theory, the dissolution process is the chemical interaction between the solutes and the solvent. Upon dissolution of salts, dissolved hydrates are formed in the aqueous solution which are analogous to the solid crystal hydrates. In 1889, Mendeleev criticized Arrhenius s theory of electrolytic dissociation. Arrhenius, in turn, did not accept the idea that hydrates exist in solutions. 

According to modem views, the basic points of the theory of electrolytic dissociation are correct and were of exceptional importance for the development of solution theory. However, there are a number of defects. The quantitative relations of the theory are applicable only to dilute solutions of weak electrolytes (up to 10 to 10 M). Deviations are observed at higher concentrations the values of a calculated with Eqs. (7.5) and (7.6) do not coincide the dissociation constant calculated with Eq. (7.9) varies with concentration and so on. For strong electrolytes the quantitative relations of the theory are altogether inapplicable, even in extremely dilute solutions. 

Hence, the theory of electrolyte solutions subsequently developed in two directions (1) studies of weak electrolyte solutions in which a dissociation equilibrium exists and where because of the low degree of dissociation the concentration of ions and the electrostatic interaction between the ions are minor and (2) studies of strong electrolyte solutions, in which electrostatic interaction between the ions is observed. 

Numerous measurements of the conductivity of aqueous solutions performed by the school of Friedrich Kohhansch (1840-1910) and the investigations of Jacobns van t Hoff (1852-1911 Nobel prize, 1901) on the osmotic pressure of solutions led the young Swedish physicist Svante August Arrhenius (1859-1927 Nobel prize, 1903) to establish in 1884 in his thesis the main ideas of his famous theory of electrolytic dissociation of acids, alkalis, and salts in solutions. Despite the sceptitism of some chemists, this theory was generally accepted toward the end of the centnry. 

This type of functional, which we refer to as coarse-grained, can be used to calculate both surface tension and adsorption isotherms to quite good accuracy for many fluids and interfaces. It can also be used for screening problems in the theory of electrolytes. 

The acidic character of acids depends on the availability ofhydrogen ions in their solution. An acid X3 is said to be stronger than another acid X2 if, in equimolar solutions, X3 provides more hydrogen ions than does X2. This will be possible provided that the degree of dissociation of X3 is greater than that of X2. Based on the Arrhenius theory of electrolytic dissociation, solutions may be classified in the manner shown in Figure 6.1. If the ionization of an acid is almost complete in water, the acid is said to be a strong acid, but if the... 

The elucidation of the electrical behavior of electrolytes owes much to Arrhenius, who was the originator of the theory of electrolytic dissociation, generally, known as the ionic theory. 

An exact description of the acidity of solutions and correlation of the acidity in various solvents is one of the most important problems in the theory of electrolyte solutions. In 1909, S. P. L. S0rensen suggested the logarithmic definition of acidity for aqueous solutions considering, at that time, of course, hydrogen instead of oxonium ions (cf. Eq. (1.4.11))... 

On the Theory of Electrolytes. I. Freezing Point Depression and Related Phenomena. (Zur Theorie der Elektrolyte. I. Gefrierpunktsemiedrigung und verwandte Erscheinun-gen). P. Debye and E. Huckel (Submitted February 27,1923), Translated from Physikalis-che Zeilschrift, Vol. 24, No. 9, 1923, pages 185-206, Classic Papers from the History of... 

De Broukere mean diameter, 18 135 Debt capital cost, 9 542 Debt ratio (DR), 9 541 Debt structure, 9 542-543 Deburring, surface, 9 597-598 Debutanizer, 10 614—615 Debye-Huckel theory, of electrolytes, 3 415 18... 

Another defect problem to which the ion-pair theory of electrolyte solutions has been applied is that of interactions to acceptor and donor impurities in solid solution in germanium and silicon. Reiss73>74 pointed out certain difficulties in the Fuoss formulation. His kinetic approach to the problem gave results numerically very similar to that of the Fuoss theory. A novel aspect of this method was that the negative ions were treated as randomly distributed but immobile while the positive ions could move freely. 

Nielsen, A. E. (1981), "Theory of Electrolyte Crystal Growth. The Parabolic Rate Law", Pure Appl. Chem. 53, 2025-2039. 

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