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Monoprotic Acid-Base Equilibria: Exact and Approximate Options
Published in Harry L. Pardue, Chemical Equilibria, 2018
Either way the reaction and autoprotolysis constants are written, the activity-based autoprotolysis constant for water at 25 °C is Kw = 1.0 × 10−14. The simpler forms of the reaction and equation are used herein.
Development of electrochemical DPD molecular simulations for oil/water partitioning of organic acids at varying pH
Published in Journal of Dispersion Science and Technology, 2018
R. Skartlien, A. Bertheussen, S. Simon, J. Sjöblom
The autoprotolysis of water incorporates these two reactions in succession, summarized by . For a basic solution, the hydronium concentration is negligible and would be too small to be measured in the simulation domain. Thus, the formation of hydronium is not incorporated in the simulations for high pH. The associated pH is then estimated by using the autoionization equilibrium constant of water, which gives pH = 14 + log[OH−]. Similarly, for an acidic solution the hydroxyl concentration is negligible, and the formation of hydroxyl is not incorporated in the simulations. The hydronium concentration can now be used directly to estimate the pH.
Non-linear boundary condition for non-ideal electrokinetic equations in porous media
Published in Applicable Analysis, 2022
Grégoire Allaire, Robert Brizzi, Christophe Labbez, Andro Mikelić
We now consider a Ca (OH) salt, meaning that there are 3 different ions, , OH and Ca, in the electrolyte. All computations are performed for the MSA model. We vary the bulk concentration of Ca (OH) from to . From this reservoir concentration we have to deduce the activities of the three ions. In a first step, the activities of the ions Ca and OH are calculated following the process explained in Section 3 of [6]. The main idea to compute these activities is to impose a bulk electroneutrality condition, ensuring that a constant zero surface charge density yields a zero potential. In a second step, knowing the activity of the ion , the pH of the solution is deduced from the autoprotolysis reaction of water and . Eventually, the activity is obtained by . The activity is chosen as our characteristic concentration which is used in the adimensionalization process (62). For a concentration mM of Ca (OH) the potential Ψ is plotted on Figure 10. The same computation is performed, replacing the non-linear boundary condition by its constant average , as defined in (83). The difference between the two resulting potentials is plotted in Figure 11. The largest differences are located at the junctions of the channels, but everywhere the relative difference is of the order of a few percent.