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The van der Waals equation is a mathematical formula that describes the behavior of real gases. It is named after Dutch physicist Johannes Diderik van der Waals . It is an equation of state that relates the pressure , temperature , and molar volume in a fluid .
The following table lists the Van der Waals constants (from the Van der Waals equation) for a number of common gases and volatile liquids. [ 1 ] To convert from L 2 b a r / m o l 2 {\displaystyle \mathrm {L^{2}bar/mol^{2}} } to L 2 k P a / m o l 2 {\displaystyle \mathrm {L^{2}kPa/mol^{2}} } , multiply by 100.
The van der Waals equation predicts that at low temperatures liquids sustain enormous tension---a fact that has led some authors to take the equation lightly. In recent years measurements have been made that reveal this to be entirely correct. [ 43 ]
The van der Waals equation of state may be written as (+) =where is the absolute temperature, is the pressure, is the molar volume and is the universal gas constant.Note that = /, where is the volume, and = /, where is the number of moles, is the number of particles, and is the Avogadro constant.
In molecular physics and chemistry, the van der Waals force (sometimes van de Waals' force) is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds , these attractions do not result from a chemical electronic bond ; [ 2 ] they are comparatively weak and therefore more susceptible to disturbance.
According to van der Waals, the theorem of corresponding states (or principle/law of corresponding states) indicates that all fluids, when compared at the same reduced temperature and reduced pressure, have approximately the same compressibility factor and all deviate from ideal gas behavior to about the same degree. [1] [2]
Johannes Diderik van der Waals (Dutch pronunciation: [joːˈɦɑnəz ˈdidərɪk fɑn dər ˈʋaːls] ⓘ; [note 1] 23 November 1837 – 8 March 1923) was a Dutch theoretical physicist and thermodynamicist famous for his pioneering work on the equation of state for gases and liquids. Van der Waals started his career as a schoolteacher.
The van der Waals surface of a molecule is an abstract representation or model of that molecule, illustrating where, in very rough terms, a surface might reside for the molecule based on the hard cutoffs of van der Waals radii for individual atoms, and it represents a surface through which the molecule might be conceived as interacting with other molecules.