Acid-base dissociation constant of water in liquid ammonia

Schindewolf, U.; Schwab, H.

doi:10.1021/j150619a001

Cited by 7 publications

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“…The experimental conditions of the unit operation can be deduced from the liquid-vapour equilibria of the two major components: water-ammonia mixtures. The diagram was calculated from the experimental data [16][17][18][19][20] by taking into account the solvation phenomena by means of the chemical equilibrium.…”

Section: Liquid-vapour Equilibriamentioning

confidence: 99%

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From the dilute solution to the pure compound: Extraction strategy based on a multi-stage process of phase separation

2010

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It is very rare that a one-step process of extraction leads to the pure compound with a high degree of purity specified by an industrial application. The various stages of a synthesis process and possible secondary reactions may lead to the synthesis of more or less complex and highly diluted solutions. In this work, the rationale and strategy for extraction and purification of a high added value compound are discussed. All the thinking is based on the knowledge and the exploitation of phase diagrams and then developed for different unit operations of the process. The most significant research tools are the experimental data and the modelling of phase equilibrium to estimate the yield of each step of extraction. The significant example chosen involves all the basic methods of phase separation, starting with liquid-vapour equilibrium: stripping of high volatility components and then more or less complex distillation are classically employed. The theoretical plateau number can be deduced from the equilibrium equation curves. The second step is based on the study of the liquid-liquid equilibrium and is an intermediate step for enrichment of the solution when distillation is not possible. A final step based on solid-liquid equilibrium consists of the selective crystallization of the pure product at low temperature, in order to satisfy the requirements of purity and safety imposed by industrial use. The conclusion includes all isolation operations in the form of a general extraction and purification scheme.phase diagram, azeotropic distillation, liquid-liquid extraction, selective crystallization

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Section: Liquid-vapour Equilibriamentioning

confidence: 99%

“…Liquid-vapour equilibria of the water-ammonia binary system at various pressures (composition expressed in molar percent of NH 3 ; □, experimental data under 1 bar[16][17][18][19][20]; -, calculated curves).…”

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From the dilute solution to the pure compound: Extraction strategy based on a multi-stage process of phase separation

2010

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Thermodynamics and Electrochemistry of Simple Ions in Ammonia

Schindewolf

1982

Ber Bunsenges Phys Chem

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A compilation of the thermodynamics of simple ions in ammonia is given, based on thermodynamic data of their salts, on some electrochemical data and on those of solvated electrons. The final data are expressed in terms of the solvation enthalpies, solvation entropies and electrode potentials of the ions. With the uncertainties of the work function of the metals and that of the surface potential of the solvent, the concept that solvated electrons are partner of any redox equilibria allows the calculation of the “absolute” electrode equilibrium potential of any electrode in contact with the solution of any redox pair. This is exemplified for a cesium and a silver electrode in ammonia. ‐ Finally the differences in the kinetics of solvated electrons in water and in ammonia with respect to the reaction with the solvent are expressed qualitatively by the transition state theory making use of the thermodynamic data of the solvated electrons. The high stability of electrons in ammonia is due to their very high positive partial molar entropy.

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Kinetics of the Reaction of Solvated Electrons with Water in Liquid Ammonia

Telser

Schindewolf

1984

Ber Bunsenges Phys Chem

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We are very grateful to Professor E. U. Franck (UniversitLt Karlsruhe) for his interest in the research program of our laboratory and for his kindness in providing us with the cooperation of the skilful personnel of the workshop at the Institut fur Physikalische Chemie und Elektrochemie, who built the cell employed in this work (method I[) following a design which was developed at the Institut.The authors are also grateful to SUBCYT (Argentina) for partial economic support. [I1 121 131 References R. Crovetto, R. Fernandez-Prini, and M. L. Japas, J. Chem. Chemical Kinetics / Isotope Effects / Photochemistry Solvated electrons (< M) produced by flash photolysis in ammonia react with water according to the rate law d[e-]/dt = k . [e-] . [H20]with the rate constant k = 0.16 k 0.03 M-' sec-' at -40°C. The rate law is compatible with the reaction e-+ H 2 0 + H + OH-, but the activation energy E, (e-) = 6 ?C 1 kJ/mol is too small for this endothermic process with AH' = 52 kJ/mol. Therefore we conclude that in the rate determining step an unknown intermediate is formed which in turn recombines to molecular hydrogen. Evidence for this intermediate was given already 15 years ago in the pure aqueous system in which solvated electrons a few msec after their reaction could be regenerated by a photo flash too soft to photo-generate them directly. -The reaction of very low concentrated metal ammonia solutions with water follows the same kinetics. But at higher concentrations (0.1 M) the relative reaction rate is very low. With sodium the reaction is slower than with cesium, in deutero-ammonia it is slower than in normal ammonia. It is almost of zero order with respect to the metal and of one half order with respect to water and has an activation energy E,(Na) = 32 * 3 kJ/mol (normal sodium-ammonia solution). The observed kinetics suggest that the solvated electrons are still the only reactive species in these solutions; but their concentration is lower than the metal concentration by many orders of magnitude due to the well known spin pairing equilibrium, which must include a metal cation and a solvent molecule. The stability of the spin paired species increases with decreasing cation size and with increasing tendency of the solvent to form hydrogen bridges. The high experimental activation energy is partly due to the temperature dependence of the spin pairing equilibrium.exothermic and very fast. The corresponding reactions in ammonia (-40°C)

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Acid-base dissociation constant of water in liquid ammonia

Cited by 7 publications

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From the dilute solution to the pure compound: Extraction strategy based on a multi-stage process of phase separation

From the dilute solution to the pure compound: Extraction strategy based on a multi-stage process of phase separation

Thermodynamics and Electrochemistry of Simple Ions in Ammonia

Kinetics of the Reaction of Solvated Electrons with Water in Liquid Ammonia

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