Properties of gases
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Graham's law of effusion
Gases : Graham's Laws of Diffusion and Effusion
Only a few physical properties of gases depends on the identity of the gas.
Diffusion - The rate at which two gases mix.
Effusion - The rate at which a gas escapes through a pinhole into a vacuum. Thomas Graham
Graham's Law of Diffusion
The rate at which gases diffuse is inversely proportional to the square root of their densities.
Since volumes of different gases contain the same number of particles (see Avogadro's Hypothesis), the number of moles per liter at a given T and P is constant. Therefore, the density of a gas is directly proportional to its molar mass (MM).
Combined gas law
The combined gas law is a gas law which combines Charles's law, Boyle's law, and Gay-Lussac's law. These laws each relate one thermodynamic variable to another mathematically while holding everything else constant. Charles's law states that volume and temperature are directly proportional to each other while pressure is held constant. Boyle's law asserts that pressure and volume are inversely proportional to each other at fixed temperature. Finally Gay-Lussac's law introduces a direct proportionality between temperature and pressure at constant volume. The inter-dependence of these variables is shown in the combined gas law, which states that:
“
The ratio between the pressure-volume constant and the temperature of a system remains constant.
”
This can be stated mathematically as
where:
P is the pressure.
V is the volume.
T is the temperature (measured in kelvin).
k is a constant with units of energy divided by temperature.
For comparing the same substance under two different sets of conditions, the law can be written as:
The addition of Avogadro's law to the combined gas law yields the ideal gas law.
Retrieved from http://en.wikipedia.org/wiki/Combined_gas_law
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