Van der Waals area

Values for hydrocarbons other than alkynes and alkadienes can be predicted by the method of Suzuki et al. The best model includes the descriptors T, P, the parachor, the molecular surface area (which can be approximated by the van der Waals area), and the zero-order connectivity index. Excluding alkynes and alkadienes, a studv for 58 alkanes, aromatics, and cycloalkanes showed an average deviation from experimental values of about 30 K. 

Over the past twenty years many volume or "bulk" parameters have been proposed, Including Van der Waals (Vw) Traube (Vt) molar (Vm) and molal (V ) volumes parachor (Pch), group molar refraotlvlty (MR) and molecular weight (li ) (2). The use of surface areas such as the Van der Waals area (A ) as parameters has also been proposed. As we remarked previously there has been much disagreement as to the Interpretation of correlations with these parameters. 

In the case of gas adsorption where the BET method is used, it is reasonable to select the van der Waals area of the adsorbate molecule moreover, being small or even monoatomic, surface orientation is not a major problem. In the case of adsorption from solution, however, the adsorption may be chemisorption. 

Van der waals area and volume - helpful in molecular thermodynamics... 

The compilations of Daubert and Danner (3) and Yaws (6-7) were used extensively. Van der Waals area and volume involve the surface area and volume of an atom and maybe ascertained from bond distances, contact distances and shapes of atoms. Methods of calculation are described by Bondi (1). 

In an engineering analysis, van der Waals area and volume are needed for carbon tetrachloride (CCI4). Determine van der Waals area and volume for carbon tetrachloride. 

Table 15 Van Der Waals Area and Volume - Organic Compounds... 

Van Der Waals Area and Volume (Area - cm /mol, Volume < cmVmol) Van Der Waals Area and Volume (Area - cm /mol, Volume - cmVmol) ... 

Zr) to provide ease of use in quickly locating the data by using the chemical formula. The compound name and CAS No (Chemical Abstracts Registry Number) are next provided. Values for van der Waals area and volume are given in the adjacent columns. 

The equation, which is generalized to multi-component mixtures, requires pure component data for the van der Waals area and volume parameters, and r. Additionally, the binary interaction parameters (Uj -Uj and (Wy - are also required and are generally determined from binary phase equilibrium data. Temperature dependency is incorporated in the equation, similar to the Wilson and NRTL equations. The UNIQUAC equation is applicable to many classes of components, including mixtures containing considerably dissimilar molecules, and is also applicable to liquid-liquid equilibrium systems. It can represent temperature dependency over moderate ranges but is not necessarily more accurate than simpler equations in spite of its theoretical foundation. 

Size and area parameters can be computed from other two quantities, van der Waals area Ayy and volume Vfy. This information is usually stored in the database for pure component properties. Finally, UNIQUAC has only two adjustable parameters, r,2 and T j, but these rise to four if temperature dependency is considered. 

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