Real gases – as opposed to a perfect or ideal gas – exhibit properties that cannot be explained entirely using the ideal gas law. To understand the behaviour of real gases, the following must be taken into account:
- compressibility effects;
- variable specific heat capacity;
- van der Waals forces;
- non-equilibrium thermodynamic effects;
- issues with molecular dissociation and elementary reactions with variable composition.
For most applications, such a detailed analysis is unnecessary, and the ideal gas approximation can be used with reasonable accuracy. On the other hand, real-gas models have to be used near the condensation point of gases, near critical points, at very high pressures, and in other less usual cases.
... The fugacity of a real gas is formally defined by an equation analogous to the relation between the chemical potential and the pressure of an ideal gas ... For an ideal gas the reference state depends only on pressure, and we set = 1 bar so that Now, for an ideal gas Reordering, we get This gives the chemical potential for an ideal gas in an ... For a real gas, we cannot calculate because we do not have a simple expression for a real gas’ molar volume ...
... pitching moment can be significantly influenced by real-gas effects ... pitching moments determined through inaccurate real-gas modeling ... The actual aerodynamic center of the Columbia was upstream from the calculated value due to real-gas effects ...
... where d is the molar density and where a, b, c, A, B, C, α, and γ are empirical constants ... Note that the γ constant is a derivative of constant α and therefore almost identical to 1. ...
... As the density of a gas increases with rising pressure, the intermolecular forces play a more substantial role in gas behavior which results in the ideal gas law no ... than double that temperature, electronic excitation and dissociation of the gas particles begins to occur causing the pressure to adjust to a greater number of particles (transition from gas to plasma) ... attempts to expand the boundaries of the ideal gas law was to include coverage for different thermodynamic processes by adjusting the equation to read pVn = constant and then ...
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