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Properties of Gases and Gas Mixtures
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
the term aν2 is called the force of cohesion and b the co-volume. At high pressures, all real gases obey the Van der Waals equation of state; however, it is not true at all ranges of pressures and temperatures. Table 8.1 shows the Van der Waals constants for some commonly used real gases. There are other equations of the state apart from Van der Waals equation of state. Those are Berthelot, Dieterici, and Redlich–Kwong equations of state.
Gases: background theory
Published in Michael de Podesta, Understanding the Properties of Matter, 2020
The additional a/Vm2 term in Equation 4.48 is small when the molar volume of the gas is large, but becomes significant as the molar volume is reduced. Commonly Equation 4.48 is used to model real gases with the parameters a and b determined experimentally from the small deviations of gases from PV=RT. Surprisingly, the Van der Waals Equation not only predicts deviations from ideal gas behaviour, but at small molar volumes and low temperatures, it predicts a region of solid-like behaviour.
Gases
Published in W. John Rankin, Chemical Thermodynamics, 2019
Various equations have been proposed to express the equation of state for gases that deviate significantly from ideality. One of the more common is the van der Waals equation which was derived to take account of the fact that the particles of a gas do occupy a finite space and that their interaction increases with increasing pressure: p=nRTV−nb−an2V2
Generation IV Nuclear Reactor: Coolant Materials in the Supercritical State
Published in Nuclear Science and Engineering, 2023
The development of accurate equations of state for substances is an important task of thermodynamics. The known van der Waals equation of state does not precisely describe the thermodynamic properties of sodium, lead, and bismuth. This can be illustrated by the following fact: The recommended40–42 critical compressibilities of sodium, lead, and bismuth are 0.1282, 0.2760, and 0.2718, respectively. But, according to the van der Waals equation of state, the critical compressibility of these metals, in general of all substances, is 0.375. This fact points out the need for the modification of the known van der Waals equation of state. To improve the accuracy in determining the thermodynamic properties of substances, the known two-parameter van der Waals equation of state is modified by introducing the parameters and in the expression for molecular pressure. The four-parameter generalized van der Waals equation of state for 1 mole of substance has the following form:
A four-parameter generalized van der Waals equation of state: theoretical determination of thermodynamic stability boundary and vapor–liquid equilibrium of vanadium, niobium and tantalum
Published in Phase Transitions, 2023
Ramesh Arumugam, Balasubramanian Ramasamy
In spite of its theoretical basis, the known van der Waals equation of state does not accurately describe the thermodynamic properties of substances. This discrepancy can be ascribed to the inaccurate attractive term in the van der Waals equation of state. To improve the accuracy of the known two-parameter van der Waals equation of state, it is proposed to introduce two new parameters in its attractive term. Such a four-parameter generalized van der Waals equation of state for one mole of substance has the form: where is the temperature, is the pressure, is the molar volume and is the universal gas constant. The parameter represents the force constant; represents the covolume, and are measures of the intermolecular attractive forces. The substance-specific constants and may be calculated through experimental data on the thermodynamic properties of substances. In fact, the parameters of any characteristic point in the phase diagram of substances may be used for determining the equation-of-state parameters. However, the use of the critical-point parameters and the Riedel’s parameter in determining the equation-of-state parameters will improve its ability to describe the thermodynamic properties of substances in the high temperature region.