Solution of electrolyte

Debye-Hiickel theory The activity coefficient of an electrolyte depends markedly upon concentration. Jn dilute solutions, due to the Coulombic forces of attraction and repulsion, the ions tend to surround themselves with an atmosphere of oppositely charged ions. Debye and Hiickel showed that it was possible to explain the abnormal activity coefficients at least for very dilute solutions of electrolytes. 

Derjaguin, B.V. and Landau, L., 1941. The stability of strongly charged lyophobic sols and the adhesion of strongly charged particles in solutions of electrolytes. Acta Physicochim, UPSS, 14, 633-662. 

When paint films are immersed in water or solutions of electrolytes they acquire a charge. The existence of this charge is based on the following evidence. In a junction between two solutions of potassium chloride, 0 -1 N and 0 01 N, there will be no diffusion potential, because the transport numbers of both the and the Cl" ions are almost 0-5. If the solutions are separated by a membrane equally permeable to both ions, there will still be no diffusion potential, but if the membrane is more permeable to one ion than to the other a diffusion potential will arise it can be calculated from the Nernst equation that when the membrane is permeable to only one ion, the potential will have the value of 56 mV. 

A careful examination has been made of the properties of / films when immersed in solutions of electrolytes. It was found that when a film of a pentaerythritol alkyd varnish was transferred from 0-001 N KCl to 3-5 N KCI its resistance rose, fell upon returning it to the 0-001 N KCl, rose again to the same high value when immersed in a sucrose solution isotonic with 3 - 5 N KCl and fell to the original value when returned to the dilute KCl solution (Fig. 14.3). It was concluded that the changes in resistance were dependent only upon the available water in the solution and were associated, therefore, with the entry of only water into the varnish film . 

Steady-state potential comparable with Type 1 reversible electrode Metal in a solution of electrolyte in which ions are produced by a corrosion reaction in an VAf exchange that determines the potential. Zn in NaCI solution Zn in dilute HCI... 

Introduction to the Study of Physical Chemistry Physical Organic Chemistry Solutions of Electrolytes Henderson and Fernelius—... 

The measurements of a by means of the electrical conductivity show that the dilution law holds good for weak electrolytes (a small), but for strong electrolytes (a large) it fails utterly. This behaviour has given rise to a considerable amount of discussion, a critical review of which will be found in a paper by the author ( Ionic Equilibrium in Solutions of Electrolytes ) in the Trans. Chem. Soc., 97, 1158, 1910. It appears that in this... 

The difficulties engendered by a hypothetical liquid standard state can be eliminated by the use of unsymmetrically normalized activity coefficients. These have been used for many years in other areas of solution thermodynamics (e.g., for solutions of electrolytes or polymers in liquid solvents) but they have only recently been employed in high-pressure vapor-liquid equilibria (P7). 

The measurement of change in the surface potentials of aqueous solutions of electrolytes caused hy adsorption of ionophore (e.g., crown ether) monolayers seems to he a convenient and promising method to ascertain selectivity and the effective dipole moments of the ionophore-ion complexes created at the water surface. 

As a result of these electrostatic effects aqueous solutions of electrolytes behave in a way that is non-ideal. This non-ideality has been accounted for successfully in dilute solutions by application of the Debye-Huckel theory, which introduces the concept of ionic activity. The Debye-Huckel Umiting law states that the mean ionic activity coefficient y+ can be related to the charges on the ions, and z, by the equation... 

Ionic activity essentially represents the concentration of a particular type of ion in aqueous solution and is important in the accurate formulation of thermodynamic equations relating to aqueous solutions of electrolytes (Barrow, 1979). It replaces concentration because a given ion tends not to behave as a discrete entity but to gather a diffuse group of oppositely charged ions around it, a so-called ionic atmosphere. This means that the effective concentration of the original ion is less than its actual concentration, a fact which is reflected in the magnitude of the ionic activity coefficient. 

As in the case of solutions, the specific conductance, K, the equivalent conductance, a, and the molar conductance, am, are also distinguished for molten electrolytes. These are defined in the same manner as done for the case of solutions of electrolytes. It may, however, be pointed out that molten salts generally have much higher conductivities than equivalent aqueous systems. 

In electronic conductors, e.g., a metallic material such as a copper wire, all the current is carried by the electrons, and for such conductors N = 1 and N+ = 0. For solutions of electrolytes it is not at all easy to ascertain what fraction of the current is carried past a certain position in the electrolyte by the cations and what fraction is carried by the anions. 

One of the first scientists to place electrochemistry on a sound scientific basis was Michael Faraday (1791-1867). On the basis of a series of experimental results on electrolysis, in the year 1832 he summarized the phenomenon of electrolysis in what is known today as Faraday s laws of electrolysis, these being among the most exact laws of physical chemistry. Their validity is independent of the temperature, the pressure, the nature of the ionizing solvent, the physical dimensions of the containment or of the electrodes, and the voltage. There are three Faraday s laws of electrolysis, all of which are universally accepted. They are rigidly applicable to molten electrolytes as well as to both dilute and concentrated solutions of electrolytes. 

The activity coefficient of the solvent remains close to unity up to quite high electrolyte concentrations e.g. the activity coefficient for water in an aqueous solution of 2 m KC1 at 25°C equals y0x = 1.004, while the value for potassium chloride in this solution is y tX = 0.614, indicating a quite large deviation from the ideal behaviour. Thus, the activity coefficient of the solvent is not a suitable characteristic of the real behaviour of solutions of electrolytes. If the deviation from ideal behaviour is to be expressed in terms of quantities connected with the solvent, then the osmotic coefficient is employed. The osmotic pressure of the system is denoted as jz and the hypothetical osmotic pressure of a solution with the same composition that would behave ideally as jt. The equations for the osmotic pressures jt and jt are obtained from the equilibrium condition of the pure solvent and of the solution. Under equilibrium conditions the chemical potential of the pure solvent, which is equal to the standard chemical potential at the pressure p, is equal to the chemical potential of the solvent in the solution under the osmotic pressure jt,... 

Weissenbom PK, Pugh RJ (1996) Surface tension of aqueous solutions of electrolytes relationship with hydration, oxygen solubility, and bubble coalescence. J Colloid Interface Sci 184 550-553... 

Klechkovskaya, N. N. Maslov, V. N. Muradov, M. B. 1989. Growth and structure of semiconducting films of CdS, ZnS, and solid solutions based on them, obtained by the mechanisms of chemisorption from solutions of electrolytes. Soviet Physics Crystallogr. 34 105-107. 

Predicting Vapor-Liquid-Solid Equilibria in Multicomponent Aqueous Solutions of Electrolytes... 

For non-electrolytes in solutions of electrolytes the prediction of activity coefficients for these species is not nearly as advanced. Most predictions are variations of the well-known Setschenow equation. 

Hypothetical water vapor activity for a hypothetical pure solution of electrolyt... 

A proper understanding of the properties of solutions of electrolytes begins with that of sodium chloride, the common salt. It is a typical example of a strong electrolyte and its characteristics in the solid state and in the dissolved state in aqueous... 

Elaborate procedures have been developed for obtaining activity coefficients from freezing-point and thermochemical data. However, to avoid duplication, the details will not be outlined here, because a completely general discussion, which is applicable to solutions of electrolytes as well as to nonelectrolytes, is presented in Chapter 21 of the Third Edition of this book [6]. 

The greater sensitivity, and hence usefulness, of g over 71, for solutions of electrolytes can be observed from the values in the third and fourth columns of Table 19.3. 

For aqueous solutions of electrolytes, a concise method of tabulating such entropy data is in terms of the individual ions, because entropies for the ions can be combined to give information for a wide variety of salts. The initial assembling of the ionic entropies generally is carried out by a reverse application of Equation (7.26) that is, Af6m of a salt is calculated from known values of AfG and AfFT for that salt. After a suitable convention has been adopted, the entropy of formation of the... 

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