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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
Until 1982, STP was defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of 101.325 kPa (1 atm). Since 1982, STP is defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of 100 kPa (1 bar). Conversions between each volume flow metric are calculated using the following formulas: Prior to 1982,
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 ...
Specific volume is commonly applied to: Molar volume; Volume (thermodynamics) Partial molar volume; Imagine a variable-volume, airtight chamber containing a certain number of atoms of oxygen gas. Consider the following four examples: If the chamber is made smaller without allowing gas in or out, the density increases and the specific volume ...
Molar volume is given by = /, where is the Avogadro constant, is the volume, and is the number of molecules (the ratio / is the amount of substance, a physical quantity with the base unit mole). When van der Waals created his equation, few scientists believed that fluids were composed of rapidly moving particles.
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.
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.