Difference between revisions of "Development of the Hydronium Ion for MSE"
(Created page with " == Hydronium Ion (H3O+) == The hydrogen ion (H<sup>+</sup>) has been replaced by the hydronium ion (H<sub>3</sub>O+) in MSEPUB. The major reason for doing this is to improve...") |
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2H<sub>2</sub>O → H<sub>3</sub>O<sup>+</sup> + OH<sup>-</sup> | 2H<sub>2</sub>O → H<sub>3</sub>O<sup>+</sup> + OH<sup>-</sup> | ||
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+ | The net result of these two equations is: | ||
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+ | H<sub>3</sub>O<sup>+</sup> = H<sub>2</sub>O + H<sup>+</sup> | ||
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+ | In order to keep predictions the same for dilute solutions it is necessary for [[File:Delta image.jpg]] of this reaction to be equal to 0. Since [[File:Delta image.jpg]] for H+ is equal to 0 at all temperatures and pressures this means that [[File:Delta image.jpg]] for H<sub>3</sub>O<sup>+</sup> has to equal [[File:Delta image.jpg]] for H<sub>2</sub>O at all temperatures and pressures. In OLI’s thermodynamic framework this requires the development of Helgeson parameters for H<sub>3</sub>O<sup>+</sup> by matching [[File:Delta image.jpg]] for H<sub>2</sub>O as closely as possible. This was done for a temperature range of 0 to 300<sup> [[File:Degree symbol.jpg]]</sup>C and for pressures up to over 1000 atmospheres. | ||
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+ | The attached figure compares the predicted pH for water using the H<sup>+</sup> and H<sub>3</sub>O<sup>+</sup> ions. The largest difference is about 0.001 pH units. | ||
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+ | [[File:Hydronium image.jpg]] |
Latest revision as of 10:04, 15 July 2016
Hydronium Ion (H3O+)
The hydrogen ion (H+) has been replaced by the hydronium ion (H3O+) in MSEPUB. The major reason for doing this is to improve the prediction of properties for strong acids. As a result of doing this, the ionization of water is changed from:
H2O → H+ + OH-
To:
2H2O → H3O+ + OH-
The net result of these two equations is:
H3O+ = H2O + H+
In order to keep predictions the same for dilute solutions it is necessary for of this reaction to be equal to 0. Since for H+ is equal to 0 at all temperatures and pressures this means that for H3O+ has to equal for H2O at all temperatures and pressures. In OLI’s thermodynamic framework this requires the development of Helgeson parameters for H3O+ by matching for H2O as closely as possible. This was done for a temperature range of 0 to 300 C and for pressures up to over 1000 atmospheres.
The attached figure compares the predicted pH for water using the H+ and H3O+ ions. The largest difference is about 0.001 pH units.