Ideal Gas Laws
There are several gas laws, three which were ultimately combined into one commonly used by introductory chemistry students. As the name implies, there are assumptions behind the ideal gas laws, and other gas laws provide more accuracy when needed, for example an equation of state called the Van der Waals equation.
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Boyle's Law
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Boyle's law states that, if the temperature of a gas is held constant throughout, then pressure times volume remains constant as well.
Charles's Law
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Charles's Law states that, if the pressure of a gas is held constant throughout, then volume divided by (absolute) temperature will also be constant.
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Gay-Lussac's Law
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In 1802, it was discovered that, for fixed volume, pressure is directly proportional to (absolute) temperature.
The Combined Formula
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The combined formula of these laws is written PV=nRT, where R is the universal gas constant (8.3145 J/(mol K)), a constant of proportionality. "n" is the moles of the gas. A mole is the molecular weight of a molecule expressed in grams.
Atmospheric Sciences
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Atmospheric sciences divide through by V since they don't deal in volume easily. "n" gets replaced with mass density (as opposed to molar density). Writing P=density---RT may be neater, since you don't have to write in terms of moles and volume anymore, but R now varies by gas.
An Ideal
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Ideal gases are called "ideal" because they presume no attractive intermolecular (Van der Waals) forces and they presume the molecules have no volume.
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Comments
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cwd2718
Mar 31, 2010
There should be a Pa in the universal gas constant units.
