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Real gases are non-ideal gases whose molecules occupy space and have interactions; consequently, they do not adhere to 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;
For example, the Mach number evolution of an ideal gas in a supersonic nozzle depends only on the heat capacity ratio (namely on the fluid) and on the exhaust-to-stagnation pressure ratio. [6] Considering real-gas effects, instead, even fixing the fluid and the pressure ratio, different total states yield different Mach profiles. [17]
Note from these that (/) (/) =; the van der Waals saturated vapor is an ideal gas in this limit. To paraphrase Sommerfeld, it is remarkable that the theory due to van der Waals is able to predict that when s g − s f ≫ 2 R {\displaystyle s_{g}-s_{f}\gg 2R} the saturated vapor behaves like an ideal gas; the saturated vapor of real gases ...
The ideal gas model has been explored in both the Newtonian dynamics (as in "kinetic theory") and in quantum mechanics (as a "gas in a box"). The ideal gas model has also been used to model the behavior of electrons in a metal (in the Drude model and the free electron model), and it is one of the most important models in statistical mechanics.
This is the virial equation of state and describes a real gas. Since higher order virial coefficients are generally much smaller than the second coefficient, the gas tends to behave as an ideal gas over a wider range of pressures when the temperature reaches the Boyle temperature (or when c = 1 V m {\textstyle c={\frac {1}{V_{m}}}} or P ...
Their predictions are the same for ideal gases. However, for real (non-ideal) gases, the results differ. [3] Dalton's law of partial pressures assumes that the gases in the mixture are non-interacting (with each other) and each gas independently applies its own pressure, the sum of which is the total pressure.
The van der Waals interactions between gas molecules, is the reason why modeling a "real gas" is more mathematically difficult than an "ideal gas". Ignoring these proximity-dependent forces allows a real gas to be treated like an ideal gas, which greatly simplifies calculation. Isothermal curves depicting the non-ideality of a real gas.
In thermodynamics, the compressibility factor (Z), also known as the compression factor or the gas deviation factor, describes the deviation of a real gas from ideal gas behaviour. It is simply defined as the ratio of the molar volume of a gas to the molar volume of an ideal gas at the same temperature and pressure .