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The molar volume of gases around STP and at atmospheric pressure can be calculated with an accuracy that is usually sufficient by using the ideal gas law. The molar volume of any ideal gas may be calculated at various standard reference conditions as shown below: V m = 8.3145 × 273.15 / 101.325 = 22.414 dm 3 /mol at 0 °C and 101.325 kPa
The ideal gas equation can be rearranged to give an expression for the molar volume of an ideal gas: = = Hence, for a given temperature and pressure, the molar volume is the same for all ideal gases and is based on the gas constant: R = 8.314 462 618 153 24 m 3 ⋅Pa⋅K −1 ⋅mol −1, or about 8.205 736 608 095 96 × 10 −5 m 3 ⋅atm⋅K ...
The proportionality constant, , when written in the form used above, has the dimension [pv 2] (pressure times molar volume squared), which is also molar energy times molar volume. The Sutherland potential (orange) represents two hard spheres that attract according to an inverse power law, and the Lennard-Jones potential (black) represents the ...
The van der Waals equation of state may be written as (+) =where is the absolute temperature, is the pressure, is the molar volume and is the universal gas constant.Note that = /, where is the volume, and = /, where is the number of moles, is the number of particles, and is the Avogadro constant.
One example of standard conditions for the calculation of SCCM is = 0 °C (273.15 K) [1] and = 1.01 bar (14.72 psia) and a unity compressibility factor = 1 (i.e., an ideal gas is used for the definition of SCCM). [2] This example is for the semi-conductor-manufacturing industry.
It is empirically true that this volume is about 0.26V c (where V c is the volume at the critical point). This approximation is quite good for many small, non-polar compounds – the value ranges between about 0.24V c and 0.28V c. [12] In order for the equation to provide a good approximation of volume at high pressures, it had to be ...
Compressibility factor values are usually obtained by calculation from equations of state (EOS), such as the virial equation which take compound-specific empirical constants as input. For a gas that is a mixture of two or more pure gases (air or natural gas, for example), the gas composition must be known before compressibility can be calculated.
The mean free path was also uncertain. Nevertheless, Loschmidt arrived at a diameter of about one nanometre, of the correct order of magnitude. Loschmidt's estimated data for air give a value of n 0 = 1.81 × 10 24 m −3. Eight years later, Maxwell was citing a figure of "about 19 million million million" per cm 3, or 1.9 × 10 25 m −3. [4]