Arrhenius electrolyte theory

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. 

Such a chemical approach which links ionic conductivity with thermodynamic characteristics of the dissociating species was initially proposed by Ravaine and Souquet (1977). Since it simply extends to glasses the theory of electrolytic dissociation proposed a century ago by Arrhenius for liquid ionic solutions, this approach is currently called the weak electrolyte theory. The weak electrolyte approach allows, for a glass in which the ionic conductivity is mainly dominated by an MY salt, a simple relationship between the cationic conductivity a+, the electrical mobility u+ of the charge carrier, the dissociation constant and the thermodynamic activity of the salt with a partial molar free energy AG y with respect to an arbitrary reference state ... 

Experiment 2 Molar Conductivity Measurements Considering Arrhenius s electrolytic theory of dissociation, Werner noted that evidence for his coordination theory may be obtained by determining the electrolytic conductivity of the metal complexes in solution. Werner and Jprgensen assumed that acid (ionic) residues bound directly to the metal would not dissociate and would thus behave as nonconductors, while those loosely held would be conductors. Molar conductivities of 0.1 molar percent aqueous solutions of some tetravalent platinum and trivalent cobalt ammines are given in Table 2.3. 

Swedish chemist Svante August Arrhenius, recipient of the 1903 Nobel Prize in chemistry, in recognition of the extraordinary services he has rendered to the advancement of chemistry by his electrolytic theory of dissociation. ... 

Svante August Arrhenius (1859-1927), Swedish physical chemist, astrophysicist, professor at the Stockholm University, and originator of the electrolytic theory of ionic dissociation, measurements of the temperature of planets and of the solar corona, and also of the theory deriving life on Earth from outer space. In 1903, he received the Nobel Prize in chemistry for the services he has rendered to the advancement of chemistry by tis e/ec-trolytic theory of dissociation ... 

Ostwald resigned the professorship at Leipzig in 1905, after differences with the university authorities. During his period there he trained a large number of students, and directed the research of a number of workers, including British and American, who spread the new physical chemistry to all countries. The school was mainly based on Arrhenius s theory of electrolytic dissociation, van t Hoff s osmotic theory of solutions, and the applications to chemistry of the laws of thermodynamics. In 1909 Ostwald received the Nobel Prize for his work on catalysis. ... 

G. Fitzgerald, in a rambling and irrelevant memorial lecture on Helmholtz, went out of his way to attack both van t HoflF s theory of dilute solutions and Arrhenius s theory of electrolytic dissociation. The sustained opposition of... 

A treatment on the basis of complete ionisation and electrical interionic action given by S. R. Milner was much simplified by P. Debye and E. Hiickel. G. N. Lewis proposed an arbitrary function of the concentration called the fugacity /, and an activity <2, such that the laws of ideal solutions are obeyed if activities are substituted for concentrations,/c = a/c being called the activity coefficient. The theory of Debye and Hiickel shows that the activity coefficient is a function of the square root of the concentration of the completely ionised electrolyte multiplied by a factor w depending on the valencies of the ions (an effect which has no place in Arrhenius s theory) /c = i - Awc >, where is a function of temperature and the properties of the pure solvent. In place of Arrhenius s a, the degree of dissociation, a conductivity coefficient / =A/Ao (or A/Aoo), which is numerically different from/c is found from the equation where a is a constant depending on the temperature... 

Arrhenius received the 1903 Nobel Prize in chemistry for his work on electrolytes. He found that a solution conducts electricity because the solute dissociates immediately upon dissolving into electrically charged particles (ions). The movement of these ions toward oppositely charged electrodes causes the solution to be a conductor. According to Arrhenius s theory, solutions that are relatively poor conductors contain electrolytes that are only partly dissociated. Arrhenius also believed that ions exist in solution whether or not an electric current is present. In other words, the electric current does not cause the formation of ions. Remember that positive ions are cations negative ions are anions. 

Presented in 1887, Svant Arrhenius (l) theory of electrolytic dissociation, that partial dissociation of the solute into negatively and positively charged ions takes place, and his proposed method of calculating the degree of dissociation helped open the way for organized theoretical and experimental investigations of electrolyte solutions. This theory held that these ions in solution are in a state of chaotic motion similar to that in an ideal gas and that the interaction of ions in a solution does not affect their distribution and motion. 

A century ago, van t Hoff s (1 ) pioneering work on the gas-solution analogy was followed by Arrhenius (2 ) theory of partial dissociation of electrolytes in solutions. Later, electrolytes came to be classified as weak or strong with the supposition that the former are partially dissociated whereas the latter are completely dissociated in the given solvent However, with... 

This ultimately led to Svante Arrhenius s theory of electrolytic dissociation and the evolution of a new division in the chemical field, known today as physical chemistry... 

Arrhenius and Ostwald played very important roles in the early studies on add-base catalysis, one century ago. Arrhenius contributed to the definition of acids and bases, and established the dependence between the rate constants and the temperature. Additionally, he also formulated an electrolytic theory of dissociation that ultimately led to him receiving the 1903 Nobel Prize in Chemistry. Ostwald proposed useful definitions of catalysis and classifications of catalysts, but he was unable to develop a satisfactory theory of these effects. This is not surprising, in view of the very limited knowledge of the mechanisms of catalysis at his time, and of the lack of understanding of how molecular properties can influence the rates of reactions. Nevertheless, his seminal work on catalysis was rewarded by him receiving the 1909 Nobel Prize in Chemistry. 

The symbol A (or A°) represents the maximum theoretical value that the molar conductivity of an electrolyte will approach when diluted indefinitely with an inert solvent. At the beginning of this century Kohlrausch found that the molar conductivity of salts in very dilute aqueous solutions showed a linear relation with the square root of the concentration. This, Kohlrausch s square root law , was incompatible with the Arrhenius electrolytic dissociation theory (q.v.), but it has since been justified by the Debye-Hiickel-Onsager theory of interionic attraction effects, which have been shown to have a dependence. 

Svante August Arrhenius, 1859-1927, Swedish physicist and chemist, was a professor of chemistry in Stockholm. His electrolytic theory of dissociation was advanced in 1884-87. In 1903 he was awarded the Nobel Prize for chemistry in recognition of the extraordinary services he has rendered to the advancement of chemistry by his electrolytic theory of dissociation. In 1909 he was elected director of the Nobel Institute in Stockholm. Together with Paul Ehrlich, he studied the toxins and antitoxins. Paul Ehrlich and Sahachiro Hata discovered salvarsan Ehrlich (1854-1938) shared with Ilja IljiC MeCnikov (1845-1916) the Nobel Prize for medicine in 1908. 

On Thalen, see Widmalm, Det oppna laboratoriet (note 54), 77-130, especially 106-113. Thalen s atheoretical commitment became clear during his negative (although understandable) reaction toward Arrhenius s theory of electrolytical dissociation. 

Despite its initial successes, there were apparent deficiencies in Arrhenius s theory. The electrical conductivities of concentrated solutions of strong electrolytes are not as great as expected, and values of the van t Hoff factor i depend on the solution concentrations, as shown in Table 14.4. For strong electrolytes that exist completely in ionic form in aqueous solutions, we would expect i = 2 for NaCl, i = 3 for MgCl2, and so on, regardless of the solution concentration. 

This system of nomenclature has withstood the impact of later experimental discoveries and theoretical developments that have since the time of Guyton de Morveau and Lavoisier greatiy altered the character of chemical thought, eg, atomic theory (Dalton, 1802), the hydrogen theory of acids (Davy, 1809), the duahstic theory (Berzehus, 1811), polybasic acids (Liebig, 1834), Periodic Table (Mendeleev and Meyer, 1869), electrolytic dissociation theory (Arrhenius, 1887), and electronic theory and modem knowledge of molecular stmcture. 

Hydrogen was recognized as the essential element in acids by H. Davy after his work on the hydrohalic acids, and theories of acids and bases have played an important role ever since. The electrolytic dissociation theory of S. A. Arrhenius and W. Ostwald in the 1880s, the introduction of the pH scale for hydrogen-ion concentrations by S. P. L. Sprensen in 1909, the theory of acid-base titrations and indicators, and J. N. Brdnsted s fruitful concept of acids and conjugate bases as proton donors and acceptors (1923) are other land marks (see p. 48). The di.scovery of ortho- and para-hydrogen in 1924, closely followed by the discovery of heavy hydrogen (deuterium) and... 

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