Equations of state for ideal and real gases

The equation of state for a gas consisting of non-interacting point particles has the form 

The assumptions involved in dris equation clearly do not accurately describe real gases in which the atoms or molecules interact widr one another, and occupy a finite volume in space the size of which is determined by the complexity and mass of the particles. The first successful attempt to improve on the ideal equation was that of van der Waals 

The conecting term in the pressure reflects the diminution in tire impact velocity of atoms at the containing walls of tire gas due to the attraction of the internal mass of gas, and the volume term reflects the finite volume of the molecules. Data for these two constants are shown in Table 3.4. 

The interaction forces which account for the value of a in this equation arise from tire size, the molecular vibration frequencies and dipole moments of the molecules. The factor b is only related to the molecular volumes. The molar volume of a gas at one atmosphere pressure is 22.414 ImoD at 273 K, and this volume increases according to Gay-Lussac s law with increasing 

Note the smaller range of temperaaire for SO2 and H2O. This was due to lack of high temperature viscosity data.  

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