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In any case, the context and/or unit of the gas constant should make it clear as to whether the universal or specific gas constant is being referred to. [ 10 ] In case of air, using the perfect gas law and the standard sea-level conditions (SSL) (air density ρ 0 = 1.225 kg/m 3 , temperature T 0 = 288.15 K and pressure p 0 = 101 325 Pa ), we ...
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
The Dobson unit arises from the ideal gas law =, where P and V are pressure and volume respectively, and n, R and T are the number of moles of gas, the gas constant (8.314 J/(mol·K)), and T is temperature in kelvins (K). The number density of air is the number of molecules or atoms per unit volume:
Isotherms of an ideal gas for different temperatures. The curved lines are rectangular hyperbolae of the form y = a/x. They represent the relationship between pressure (on the vertical axis) and volume (on the horizontal axis) for an ideal gas at different temperatures: lines that are farther away from the origin (that is, lines that are nearer to the top right-hand corner of the diagram ...
where P is the pressure, V is the volume, N is the number of gas molecules, k B is the Boltzmann constant (1.381×10 −23 J·K −1 in SI units) and T is the absolute temperature. These equations are exact only for an ideal gas , which neglects various intermolecular effects (see real gas ).
at each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air (287.0528J⋅kg −1 ⋅K −1). The solution is given by the barometric formula. Air density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.
R is the gas constant, which must be expressed in units consistent with those chosen for pressure, volume and temperature. For example, in SI units R = 8.3145 J⋅K −1 ⋅mol −1 when pressure is expressed in pascals, volume in cubic meters, and absolute temperature in kelvin. The ideal gas law is an extension of experimentally discovered ...
In this formulation, R * is the gas constant, and the term R * T/Mg gives the scale height (approximately equal to 8.4 km for the troposphere). (For exact results, it should be remembered that atmospheres containing water do not behave as an ideal gas. See real gas or perfect gas or gas for further understanding.)