Sulfur dioxide aqueous-phase equilibrium

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. 

J. Krissmann, M. A. Siddiqi, K. Lucas, Absorption of sulfur dioxide in dilute aqueous solutions of sulfuric and hydrochloric acid, Fluid Phase Equilibriums, 1997, 141, S221-S233. 

Figure 5.8a gives the proportions of SO2 in the gas and aqueous phase as a function of pH. For pH < 5, sulfur dioxide occurs mainly in the gas phase for pH > 7, it occurs mainly in the solution phase. The fraction of SO2 in the aqueous phase is given in Figure 5.8b as a function of q (water content) for a few pH values. The double logarithmic graphic representation is particulariy convenient to plot the equilibrium distribution of the aqueous sf>ecies (Figure 5.8c). For a sketch of this diagram it is convenient to recall the following ...

Quantitative analysis of different reaction pathways for the transformation of aquated sulfur dioxide in atmospheric droplet systems has been a major objective of the research conducted in the principal investigator s laboratory for the last four years. Available thermodynamic and kinetic data for the aqueous-phase reactions of SO2 have been incorporated into a dynamic model of the chemistry of urban fog that has been developed by Jacob and Hoffmann (23) and Hoffmann and Calvert (39). The fog and cloud water models developed by them are hybrid kinetic and equilibrium models that consider the major chemical reactions likely to take place in atmospheric water droplets. Model results have verified that... 

The chemistry that occurs in cloud and fog droplets in the atmosphere has been shown, in the last decade or so, to be highly complex. Most atmospheric species are soluble to some extent, and the liquid-phase reactions that are possible lead to a diverse spectrum of products. The aspect of atmospheric aqueous-phase chemistry that has received the most attention is that involving dissolved S02. Sulfur dioxide is not particularly soluble in pure water, but the presence of other dissolved species such as H202 or 03 displaces the dissolution equilibrium for S02, effectively... 

Carbon Dioxide/Water Equilibrium 345 Sulfur Dioxide 348 Ammonia/Water Equilibrium 353 Nitric Acid/Water Equilibrium 355 Equilibrium of Other Important Atmospheric Gases Aqueous-Phase Reaction Rates 361 S(IV) to S(VI) Transformation and Sulfur Chemistry 363... 

This latter reaction is similar to the gas-phase reactions between S02" and SO2. Chemical reduction by alkali metals can also be used and work with lithium suggests that the complex 8204 also dimerizes [29]. In non-aqueous solvents, the reaction of sulfur dioxide with superoxide produces the sulfur dioxide radical anion, but with an equilibrium constant of only about =1.1 [30], reaction (16) ... 

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