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The gas constant occurs in the ideal gas law: = = where P is the absolute pressure, V is the volume of gas, n is the amount of substance, m is the mass, and T is the thermodynamic temperature. R specific is the mass-specific gas constant. The gas constant is expressed in the same unit as molar heat.
For example, check the universal gas law equation of PV = nRT, when: the pressure P is in pascals (Pa) the volume V is in cubic metres (m 3) the amount of substance n is in moles (mol) the universal gas constant R is 8.3145 Pa⋅m 3 /(mol⋅K) the temperature T is in kelvins (K)
where ℓ is the mean free path, n is the number of target particles per unit volume, ... being the specific gas constant, equal to 287 J/(kg*K) for air. The ...
The constant = / , and has dimension of molar volume, [v]. The constant expresses the strength of the hypothesized interparticle attraction. Van der Waals only had as a model Newton's law of gravitation, in which two particles are attracted in proportion to the product of their masses.
To calculate the density of air as a function of altitude, one requires additional parameters. For the troposphere, the lowest part (~10 km) of the atmosphere, they are listed below, along with their values according to the International Standard Atmosphere, using for calculation the universal gas constant instead of the air specific constant:
The atmospheric pressure is roughly equal to the sum of partial pressures of constituent gases – oxygen, nitrogen, argon, water vapor, carbon dioxide, etc.. In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. [1]
The model assumptions are: the uncompressed volume of the cylinder is one litre (1 L = 1000 cm 3 = 0.001 m 3); the gas within is the air consisting of molecular nitrogen and oxygen only (thus a diatomic gas with 5 degrees of freedom, and so γ = 7 / 5 ); the compression ratio of the engine is 10:1 (that is, the 1 L volume of uncompressed ...
For example, terrestrial air is primarily made up of diatomic gases (around 78% nitrogen, N 2, and 21% oxygen, O 2), and at standard conditions it can be considered to be an ideal gas. The above value of 1.4 is highly consistent with the measured adiabatic indices for dry air within a temperature range of 0–200 °C, exhibiting a deviation of ...