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Say I have Argon gas in an area such as a cube with pressure around pressure between 10-5 and 10-3 Torr (pressure) at 25 degrees at 320 Kelvins . How do I find the amount of atoms in that cube? Any formulas?

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up vote 2 down vote accepted

If you assume it is an ideal gas and you know the volume of the cube, the temperature of the gas, and the pressure, you can calculate the number of atoms using the ideal gas law:


Where P is pressure, V is volume, n is the nuber of moles, R is the ideal gas constant, and T is the temperature in Kelvin.

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