Electrolytes in aqueous solutions

A special corrverrtion exists concerning the free errergies of ions in aqueous solution. Most themrodyrramic iirfomration about strong (fiilly dissociated) electrolytes in aqueous solutions comes, as has been seen, from measiiremerrts of the eirrf of reversible cells. Sirrce tire ions in very dilute solution (or in the hypothetical... 

It is accurate for simple low valence electrolytes in aqueous solution at 25 °C and for molten salts away from the critical point. The solutions are obtained numerically. A related approximation is the following. 

Table 8.35 Equivalent Conductivities of Electrolytes in Aqueous Solutions at...

It is important to realise that whilst complete dissociation occurs with strong electrolytes in aqueous solution, this does not mean that the effective concentrations of the ions are identical with their molar concentrations in any solution of the electrolyte if this were the case the variation of the osmotic properties of the solution with dilution could not be accounted for. The variation of colligative, e.g. osmotic, properties with dilution is ascribed to changes in the activity of the ions these are dependent upon the electrical forces between the ions. Expressions for the variations of the activity or of related quantities, applicable to dilute solutions, have also been deduced by the Debye-Hiickel theory. Further consideration of the concept of activity follows in Section 2.5. 

The species appearing as strong electrolytes in aqueous solutions lose this property in low-permittivity solvents. The ion-pair formation converts them to a sort of weak electrolyte. In solvents of very low-permittivity (dioxan, benzene) even ion triplets and quadruplets are formed. 

Figure 3.1 Gouy-Chapman capacity for various concentrations of a 1-1 electrolyte in aqueous solution at room temperature.

The use of surface charge to provide colloid stability to particles dispersed in dilute electrolytes in aqueous solution, or even in media of intermediate polarity, is an effective means of stabilising particles against van der Waals forces of attraction. Figure 3.16 shows typical potential... 

Many of the undesirable substances present in gaseous or liquid streams form volatile weak electrolytes in aqueous solution. These compounds include ammonia, hydrogen sulfide, carbon dioxide and sulfur dioxide. The design and analysis of separation processes involving aqueous solutions of these materials require accurate representation of the phase equilibria between the solution and the vapor phase. Relatively few studies of these types of systems have been published concerning solutions of weak electrolytes. This paper will review the methods that have been used for such solutions and, as an example, consider the alkanolamine solutions used for the removal of the acid gases (H2S and C02) from gas streams. 

Bromley, L. A., "Thermodynamic Properties of Strong Electrolytes in Aqueous Solutions," AIChE J., 1973, 19, 313. 

On the Solubility of Volatile Weak Electrolytes in Aqueous Solutions... 

The solubility of gaseous weak electrolytes in aqueous solutions is encountered in many chemical and petrochemical processes. In comparison to vapory-liquid equilibria in non reacting systems the solubility of gaseous weak electrolytes like ammonia, carbondioxide, hydrogen sulfide and sulfur dioxide in water results not only from physical (vapor-liquid) equilibrium but also from chemical equilibrium in the liquid phase. 

Roughly half of the data on the activities of electrolytes in aqueous solutions and most of the data for nonelectrolytes, have been obtained by isopiestic technique. It has two main disadvantages. A great deal of skill and time is needed to obtain reliable data in this way. It is impractical to measure vapor pressures of solutions much below one molal by the isopiestic technique because of the length of time required to reach equilibrium. This is generally sufficient to permit the calculation of activity coefficients of nonelectrolytes, but the calculation for electrolytes requires data at lower concentrations, which must be obtained by other means. 

Arbuckle, R. "A Bibliography of Sources of Experimental Data Leading to Activity or Osmotic Coefficients for Polyvalent Electrolytes in Aqueous Solution" Nat. Bur. Stand. Special Publ. No. 485, July 1979. 

Hamer, W. J. "Theoretical Mean Activity Coefficients of Strong Electrolytes in Aqueous Solution from 0 to 100 C" NSRDS-NBS 24, U.S. Department of Commerce, National Bureau of Standards, December 1968. 

Goldberg, R. N., B. R. Staples, R. L. Nuttall and R. Arbuckle, (1977). "A Bibliography of Sources of Experimental Data Leading to Activity or Osmotic Coefficients for Polyvalent Electrolytes in Aqueous Solution", Nat. Bur. Stand. (U.S.) Spec. Publication 485, U.S. Gov t. Printing Office, Washington, D.C. 

Wu, Y. C. and W. J. Hamer, (1969). "Osmotic Coefficients and Mean Activity Coefficients of a Series of Uni-Bivalent and Bi-Univalent Electrolytes in Aqueous Solutions at 25°C," National Bureau of Standards Report (NBSIR) 10052, Part XIV, 83 p. 

The phase-equilibrium relation for volatile electrolytes, such as HC1, has the advantage that the electrolyte in aqueous solution... 

Millero F. J. (1972). The partial molal volumes of electrolytes in aqueous solutions. In Water and Aqueous Solutions, R. A. Home (series ed.), New York Wiley Interscience. 

Tab. 3 The effect of the supporting electrolyte (in aqueous solution) on the potential (versus SHE) of the minimum of the double-layer capacitance [11, 34] of the Au (100) electrode surface...

Diffusion coefficient of salts (electrolytes) in aqueous solutions... 

Ise, N. The Mean Activity Coefficient of Poly electrolytes in Aqueous Solutions and Its Related Properties. Vol. 7, pp. 536—593. 

Calculate the apparent value of the equivalent conductance A for each of these electrolytes in the conventional units cm2 eq-1 ohm-1. How do the A values of these compounds compare with A0 for simple electrolytes in aqueous solutions ... 

Since q ranges from 0 to n, the possible variation of B from this cause is 2.5n(VA — VB). To estimate the magnitude of the effect, let us take n = 4, and VA — VB = 0.040 1. This gives a variation of 0.40 in B. Typical values of B for simple electrolytes in aqueous solution run from about —0.1 to +0.2, so this expected variation should be easily detectable. It is clear that for a solute such as LiCl in mixtures of water with a less polar liquid, n is by no means constant over the whole range of solvent compositions, and it is effectively larger in pure water because... 

As remarked in Sidebar 3.11, soluble salts MA (M = cation, A = anion) often behave as strong electrolytes in aqueous solutions, dissociating completely into ionic species as expressed by... 

A properly balanced chemical equation shows all the information we have just discussed. Soluble salts and strong electrolytes in aqueous solution are always written in ionic form—for example, Na+ + n0 NaCl) or H+ 0r H30+)... 

Nichols, N., et al., Additivity Relations for the Heat Capacities of Non-electrolytes in Aqueous Solution. J. Chem. Thermodyn., 1976 8, 1081-1093. 

Electrolytes in Aqueous Solution 4.9 Balancing Redox Reactions ... 

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