Download - Lecture12222
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Gas State: Ideal Gas Theory and Deviations
Lecture 12
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Simpler models are more useful than
complex onesas long as they explain the
data.
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Deviation of real gases from ideal gas
behavior
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The reasons of the deviations:At moderately high pressure, values of PV/RT lower than ideal are due to intermolecular attractions.At very high pressure, values of PV/RT greater than ideal are due predominantly to molecular volume.
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To accurately describe real gas behavior, the ideal gas equation has to be redesigned:To adjust pressure up, we need to add a factor that accounts for intermolecular attractions.To adjust the measured volume down, we need to subtract a factor from the entire container volume that accounts for the molecular volume.
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Johannes Diderik van der Waals (1837–1923), a Dutch scientist
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The van der Waals equation
describes real gas behavior.Herein, a and b are van der
Waals constants.
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a and b are specific for every individual
gas.a relates to the number of electrons, which relates to the complexity of a molecule
and the strength of its intermolecular attractions.
b relates to molecular volume.
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Van der Waals constants
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THE END