Sodium sulfate activity coefficients

To demonstrate mass action, we show that for any possible reaction the activity product Q matches the equilibrium constant K. This step is most easily accomplished by computing log Q as the sum of the products of the reaction coefficients and log activities of the corresponding species. The reaction for the sodium-sulfate ion pair, for example,... 

Fig. 4 to Fig. 8 show the severe divergence for activity coefficients such as given here for calcium, chloride, sulfate, sodium and water ions, calculated with different equations. The activity coefficients were calculated applying Eq. 13 to Eq. 17 for the corresponding ion dissociation theories, whereas the values for the PITZER equations were gained using the program PHRQPITZ. The limit of validity of each theory is clearly shown. 

Figure 2. The Henry constant of oxygen in aqueous solutions of sodium sulfate at 25 °C (O) experimental data (a) the Henry constant calculated with eq 24 using for the mean activity coefficient of dissolved salt the Debye-Hiickel equation (b) the Henry constant calculated with eq 24 using for the mean activity coefficient of dissolved salt the extended Debye-Hiickel equation (c) the Henry constant calculated with eq 24 using for the mean activity coefficient of dissolved salt the Bromley equation (d) the Henry constant calculated with eq 15.

Calculate (a) the mean ionic activity coefficient and the mean ionic activity of a 0.002 mol kg aqueous solution of ephedrine sulfate (b) the mean ionic activity coefficient of an aqueous solution containing 0.002 mol kg ephedrine sulfate and 0.01 mol kg sodium chloride. Both solutions are at 25°C. 

In the experimental determination of activity coefficients of strong electrolytes, by the methods described below, the molalities, etc., of the ions are taken as the stoichiometric values, that is, the total possible molality, etc., disregarding incomplete dissociation, For example, in the last problem, the molalities of the sodium and sulfate ions in the 0.5 molal solution of sodium sulfate were taken as exactly 1.0 and 0.5, respectively, without allowing for the possibility that the salt may be only partially dissociated at the specified concentration. The activity coefficients obtained in this manner are called stoichiometric activity coefficients they allow for all variations from the postulated ideal behavior, including that due to incomplete dissociation. If the treatment is based on the actiuil ionic molalities, etc., in the given solution, as in the Debye-Httckel theory (Chapter XVII), there is obtained the true (or actual) activity coefficient. TTie ratio... 

In seawater, the differences between activities and concentrations must always be considered (cf. Sect. 15.1.1). The activity coefficients for monovalent ions in seawater assume a value around 0.75, for divalent ions this value usually lies around 0.2. In most cases of practical importance, the activity coefficients can be regarded with sufficient exactness as constants, since they are, over the whole range of ionic strengths in solution, predominately bound to the concentrations of sodium, chloride, and sulfate which are not directly involved in the calcite-carbonate-equilibrium. The proportion of ionic complexes in the overall calcium or carbonate content can mostly be considered with sufficient exactness as constant in the free water column of the ocean. Yet, this cannot be applied to pore water which frequently contains totally different concentrations and distributions of complex species due to diage-netic reactions. 

In Figure 2 the sodium-ion, dodecyl sulfate ion activities and the mean activity of the NaDS solution are plotted against the total surfactant concentration at a constant (0.224%) PVA concentration. The activity coefficients are relative to that of a 5.0xl0"3 moLkg" NaDS solution (a ). The shape of the experimental activity curves is similar to that obtained by the model calculations. At about 6 mmoLkg l concentration, which is still less than the critical micelle formation concentration (cjy = 8.1 mmol.kg ), complex formation occurs between PVA and NaDS, and above this point the mean activity increases only slightly. 

Although there is ample evidence of its existence, the NaSO ion is generally ignored when calculating activity coefficients in solutions containing sodium and sulfate ions. Sodium sulfate is treated as a completely dissociating electrolyte. As early as 1930. Righellato and Davies (S34) stated that, even in dilute solutions, most uni-bivalent salts are incompletely dissociated. Based on conductance measurements at 18 C, they presented dissociation constants for a number of intermediate ions. For the salt MzX the dissociations were defined ... 

Robinson, R.A. J.M. Wilson R.H. Stokes, "The activity coefficients of lithium, sodium and potassium sulfate and sodium thiosulfate at 25° from isopiestic vapor pressure measurements", JACS, v63, pplOll (1941)... 

Scatchard. G. Y.C. Wu. R.M. Rush. "Osmotic and activity coefficients for binary mixtures of sodium chloride, sodium sulfate, magnesium sulfate and magnesium chloride in water at 25°C. III. Treatment with the ions as components", J. Phys. Chem., v74, 21, pp3786-3796 (1970)... 

The subscript i on the variables in the above equations implies that each individual species has its own molality, activity, activity coefficient, and so on. For example, in a 1.00-molal solution of sodium sulfate (Na2S04),... 

Typical behaviour of osmotic and activity coefficients as calculated using Eqs. (5.36) and (5.37), is illustrated for trisodium citrate and tripotassium citrate in Fig. 5.15. It can be observed, that values of the (/w) and y+(/w) coefficients after a strong fall in very dilute solutions depend rather weakly on the citrate concentration. Since a T-,m) values are nearly temperature independent, the same is observed in the case osmotic and activity coefficients. It is worthwhile to mention that the Pitzer model was also used by Schunk and Maurer [163] when they determined water activities at 25 °C in ternary systems (citric acid + inorganic salt). The interactions parameters between ions, which were applied to represent activities in ternary systems, were calculated by taking into account the dissociation steps of citric acid and the formation of bisulfate ions for solutions with sodium sulfate. 

The ESR spectrum of the pyridazine radical anion, generated by the action of sodium or potassium, has been reported, and oxidation of 6-hydroxypyridazin-3(2//)-one with cerium(IV) sulfate in sulfuric acid results in an intense ESR spectrum (79TL2821). The self-diffusion coefficient and activation energy, the half-wave potential (-2.16 eV) magnetic susceptibility and room temperature fluorescence in-solution (Amax = 23 800cm life time 2.6 X 10 s) are reported. 

Consider a cation exchange resin in an aqueous solution containing Na2S04. Obtain the selectivity of the resin for the sodium cation over the sulfate anion if the activity based distribution coefficient of the anion between the resin and the external solution is 0.001. (Ans. 31, 630.)... 

---