ex7: Example 7-Gas-Phase Calculations

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This example demonstrates the capabilities of PHREEQC to model the evolution of gas compositions in equilibrium with a solution with a fixed (total) pressure or a fixed volume of the gas phase. In the case of a fixed-pressure gas phase, a gas bubble forms as soon as the sum of the partial pressures of the component gases exceeds the specified pressure of the gas phase. Once the bubble forms, its volume and composition will vary with the extent of reactions. This case applies to gas bubbles forming in surface water or groundwater at a given depth, where the total pressure is constant. With a fixed-volume gas phase, the aqueous solution is in contact with a head space of a fixed volume, which is typical for a laboratory experiment with a closed bottle. The gas phase always exists in this head space, but its pressure and composition will vary with the reactions. Another way to model gas-liquid reactions in PHREEQC is to maintain a fixed partial pressure by using the EQUILIBRIUM_PHASES data block. This fixed-partial-pressure approach is illustrated in this example by fixing the CO2 pressure for a SOLUTION. The example can be run using the phrRunString routine.





See Also

Other Examples: ex10, ex11, ex12, ex13a, ex14, ex15, ex16, ex17, ex18, ex19, ex1, ex20a, ex21, ex22, ex2, ex3, ex4, ex5, ex6, ex8, ex9



phreeqc documentation built on July 1, 2020, 11:46 p.m.