New kinetic reactions
Programs React, X1t, and X2t in the Standard and Professional editions of The Geochemist's Workbench® can trace the progress of various types of kinetic reactions: dissolution, precipitation, redox transformation, and microbial catalysis and growth. Release 9.0 of the GWB accounts for three new types of kinetic reactions, as shown below.
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GWB9 can evaluate rate expressions for the association of dissolved species to form aqueous complexes, as well as the dissociation of complex species.
To set a rate law for a complexation reaction, you specify
- The name of the complex species,
- Its onset concentration, if not at equilibrium initially,
- The rate constant for association or dissociation, and
- The orders of promoting and inhibiting species in the rate law
Click the image at left to see a React run tracing the complexation of F– with Al3+. The link below opens a step-by-step tutorial.
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React, X1t, and X2t can include in a simulation the sorption or exchange of aqueous species onto mineral surfaces, and the release of species into solution as they desorb from a surface.
You set a kinetic surface reaction by supplying
- The name of the surface complex to react kinetically,
- Its initial concentration, if not at equilibrium,
- The rate constant for sorption or desorption, and
- The orders of promoting and inhibiting species
Click the diagram at left to see a React simulation of the desorption of Ca2+ from ferric oxyhydroxide, or below for a step-by-step tutorial.
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GWB9 can evaluate rate expressions describing the dissolution of gases from an external reservoir, and the exsolution of gases into one.
To configure a kinetic gas transfer reaction, you set
- The name of the gas to be transferred,
- The fugacity of that gas in the external reservoir,
- A rate constant, and
- The contact area between fluid and reservoir, in cm2/kg water
The image at left shows the results of simulating with React the kinetic exsolution of CO2 from a fluid. The icon below opens a tutorial.