# Non-ideal gas - Van der Waals equation and constants

## Listing of van der Waals constants for more than 200 gases, used to correct for non-ideal behavior of gases caused by intermolecular forces and the volume occupied by the gas particles

The ideal gas law treats the molecules of a gas as point particles with perfectly elastic collisions. This works well for dilute gases in many experimental circumstances.

However,  gas molecules are not point masses, and there are many cases gases need to be treated as non-ideal.  Johannes D. van der Waals suggested a modification to take into account molecular size and molecular interaction forces. It is usually referred to as the van der Waals equation of state:

[P + a(n/V)2] (V/n - b) = RT

The constants a and b are called  van der Waals constants. They have positive values and are characteristic of the individual gas. If a gas behaves ideally, both a and b are zero, and van der Waals equations approaches the ideal gas law PV=nRT.

The constant a provides a correction for the intermolecular forces.
Constant b adjusts for the volume occupied by the gas particles. It is a correction for finite molecular size and its value is the volume of one mole of the atoms or molecules.

See also the Gas Compressibility Factor, z-factor for air, dependent on pressure and temperature and used to account for deviation from the ideal situation.
How to calculate total pressure and partial pressures from Ideal gas law

* To convert a into atm L2/mol2 multiply by 0.986 atm/bar.    To convert a into kPa L2/mol2 multiply by 100.0 kPa/bar

 Name Molecular Formula a* bar L2/mol2 bL/mol Aluminum trichloride AlCl3 42.63 0.245 Ammonia NH3 4.225 0.03713 Ammonium chloride NH4Cl 2.38 0.00734 Argon Ar 1.355 0.03201 Boron trichloride BCl3 15.6 0.1222 Boron trifluoride BF3 3.98 0.05443 Diborane B2H6 6.048 0.07437 Bromine Br2 9.75 0.0591 Perchloryl fluoride ClFO2 7.371 0.0713 Chlorine pentafluoride ClF5 9.58 0.08204 Phosphonium chloride ClH4P 4.111 0.04545 Chlorine Cl2 6.343 0.05422 Trichlorofluorosilane Cl3FSi 15.67 0.1273 Fluorine F2 1.171 0.02896 Germanium tetrachloride GeCl4 23.12 0.1489 Nitrogen trifluoride F3N 3.58 0.05453 Phosphorus trifluoride F3P 4.954 0.0651 Tetrafluorohydrazine F4N2 7.426 0.08564 Germane GeH4 5.743 0.06555 Helium He 0.0346 0.0238 Hydrogen bromide HBr 4.5 0.04415 Hydrogen chloride HCl 3.7 0.04061 Hydrogen cyanide HCN 11.29 0.08806 Hydrogen fluoride HF 9.565 0.0739 Hydrogen iodide HI 6.309 0.05303 Hydrogen H2 0.2453 0.02651 Water H2O 5.537 0.03049 Hydrogen sulphide H2S 4.544 0.04339 Hydrogen selenide H2Se 5.523 0.0479 Krypton Kr 2.325 0.0396 Silane SiH4 4.38 0.0579 Silicon tetrachloride SiCl4 20.96 0.147 Silicon tetrafluoride SiF4 5.259 0.07236 Titanium(IV) chloride TiCl4 25.47 0.1423 Mercury Hg 5.193 0.01057 Nitric oxide NO 1.46 0.0289 Nitrogen dioxide NO2 5.36 0.0443 Nitrogen N2 1.37 0.0387 Nitrous oxide N2O 3.852 0.04435 Hydrazine N2H4 8.46 0.0462 Neon Ne 0.208 0.01672 Oxygen O2 1.382 0.03186 Ozone O3 3.57 0.0487 Phosphorus P 53.6 0.157 Phosphine PH3 4.696 0.05157 Radon Rn 6.601 0.06239 Stannic chloride SnCl4 27.25 0.1641 Sulphur S 24.3 0.066 Sulphur dioxide SO2 6.865 0.05679 Sulphur hexafluoride SF6 7.857 0.08786 Selenium Se 33.4 0.0675 Uranium(VI) fluoride UF6 16.01 0.1128 Tungsten(VI) fluoride WF6 13.25 0.1063 Xenon Xe 4.192 0.05156 Xenon difluoride XeF2 12.46 0.07037 Xenon tetrafluoride XeF4 15.52 0.09035 Chlorotrifluoromethane CClF3 6.873 0.0811 Trichlorofluoromethane CCl3F 14.68 0.1111 Tetrachloromethane CCl4 20.01 0.1281 Tetrafluoromethane CF4 4.04 0.06325 Carbon monoxide CO 1.472 0.03948 Carbon oxysulphide COS 6.975 0.06628 Carbon dioxide CO2 3.658 0.04286 Carbon disulphide CS2 11.25 0.07262 Trichloromethane CHCl3 15.34 0.1019 Trifluoromethane CHF3 5.378 0.06403 Dichloromethane CH2Cl2 12.44 0.08689 Difluoromethane CH2F2 6.184 0.06268 Chloromethane CH3Cl 7.566 0.06477 Fluoromethane CH3F 5.009 0.05617 Nitromethane NH3NO2 17.18 0.1041 Methane CH4 2.3 0.04301 Methanol CH3OH 9.472 0.06584 Methanethiol CH3SH 8.911 0.06756 Methylamine CH3NH2 7.106 0.05879 1,1,2-Trichlorotrifluoroethane C2Cl2F3 20.25 0.1481 Tetrafluoroethylene C2F4 6.954 0.08085 Cyanogen C2N2 7.803 0.6952 Acetylene C2H2 4.516 0.0522 1,1-Difluoroethylene C2H2F2 6 0.07058 1,1,1-Trichloroethane C2H3Cl3 20.15 0.1317 Fluroethylene C2H3F 5.984 0.06504 1,1,1-Trifluoroethane C2H3F3 9.302 0.09572 Acetonitrile C2H3N 17.89 0.1169 Ethylene C2H4 4.612 0.05821 1,1-Dichloroethane C2H4Cl2 15.73 0.1072 1,2-Dichloroethane C2H4Cl2 17 0.108 Ethylene oxide C2H4O 8.922 0.06779 Acetic acid CH3COOH 17.71 0.1065 Methyl formate C2H4O2 11.54 0.08442 Bromoethane C2H5Br 11.89 0.08406 Chloroethane C2H5Cl 11.7 0.09 Fluoroethane C2H5F 8.17 0.07758 Ethane C2H6 5.57 0.06499 Dimethyl ether C2H6O 8.69 0.07742 Ethanol C2H5OH 12.56 0.0871 Dimethyl sulphide C2H5SH 13.34 0.09453 Ethanethiol C2H5SH 13.23 0.09447 Dimethylamine C2H7N 10.44 0.0851 Ethylamine C2H7N 10.79 0.08433 Perfluoropropane C3F8 12.96 0.1338 Propanenitrile C3H5N 21.57 0.1369 Propene C3H6 8.438 0.08242 Cyclopropane C3H6 8.293 0.0742 Acetone C3H6O 16.02 0.1124 Propanal C3H6O 14.08 0.09947 Ethyl formate C3H6O2 15.91 0.1115 Methyl acetate C3H6O2 15.75 0.1108 Propanoic acid C3H6O2 23.49 0.1386 1-Chloropropane C3H7Cl 16.11 0.1141` Propane C3H8 9.385 0.09044 1-Propanol C3H8O 16.26 0.108 2-Propanol C3H8O 15.82 0.1109 Ethyl methyl ether C3H8O 12.7 0.1034 Ethyl methyl sulphide C3H8S 19.45 0.13 Propylamine C3H9N 15.26 0.1094 Trimethylamine C3H9N 13.37 0.1101 Furan C4H4O 12.74 0.0926 Thiophene C4H4S 17.21 0.1058 Pyrrole C4H4N 18.82 0.1049 1,3-Butadiene C4H6 12.17 0.102 Acetic anhydride C4H6O3 26.8 0.157 Butanenitrile C4H7N 25.76 0.1568 1-Butene C4H8 12.76 0.1084 Cyclobutane C4H8 12.39 0.096 2-Butanone C4H8O 19.97 0.1326 Tetrahydrofuran C4H8O 16.39 0.1082 1,4-Dioxane C4H8O2 19.29 0.1171 Ethyl acetate C4H8O2 20.57 0.1401 Methyl propanoate C4H8O2 20.51 0.1377 Propyl formate C4H8O2 20.79 0.1377 Butanoic acid C4H8O2 28.18 0.1609 Pyrrolidine C4H9N 16.84 0.1056 Butane C4H10 13.93 0.1168 Isobutane C4H10 13.36 0.1168 1-Butanol C4H10O 20.9 0.1323 2-Methyl-2-propanol C4H10O 18.81 0.1324 2-Methyl-1-propanol C4H10O 20.35 0.1324 Diethyl ether C4H10O 17.46 0.1333 Diethyl sulphide C4H10S 22.85 0.1462 Butylamine C4H11N 19.41 0.1301 Diethylamine C4H11N 19.4 0.1383 Tetramethylsilane C4H12Si 20.81 0.1653 Furfural C5H4O2 22.23 0.1182 Pyridine C5H5N 19.77 0.1137 Cyclopentene C5H8 15.61 0.1097 1-Pentene C5H10 17.86 0.137 2-Methyl-1-butene C5H10 16.9 0.129 2-Methyl-2-butene C5H10 17.26 0.1279 Cyclopentane C5H10 16.94 0.118 Tetrahydropyran C5H10O 20.02 0.1247 Isobutyl formate C5H10O2 22.82 0.1476 Propyl acetate C5H10O2 26.23 0.17 Ethyl propanoate C5H10O2 25.86 0.1688 Methyl butanoate C5H10O2 25.83 0.1661 Methyl isobutanoate C5H10O2 24.87 0.1639 Piperidine C5H11N 20.84 0.125 Pentane C5H12 19.13 0.1451 Isopentane C5H12 18.29 0.1415 Neopentane C5H12 17.17 0.141 1-Pentanol C5H12O 25.81 0.1564 Bromobenzene C6H5Br 28.96 0.1541 Chlorobenzene C6H5Cl 25.8 0.1454 Fluorobenzene C6H5F 20.1 0.1279 Iodobenzene C6H5I 33.54 0.1658 Benzene C6H6 18.82 0.1193 Phenol C6H5OH 22.93 0.1177 Aniline C6H5NH2 29.14 0.1486 Cyclohexanone C6H10O 31.1 0.17 Hexanenitrile C6H11N 35.5 0.1996 Cyclohexane C6H12 21.95 0.1413 Cyclohexanol C6H11OH 28.93 0.1586 Pentyl formate C6H12O2 27.97 0.173 Isobutyl acetate C6H12O2 29.05 0.1845 Ethyl butanoate C6H12O2 30.53 0.1922 Ethyl 2-methylpropanoate C6H12O2 29.05 0.1872 Methyl pentanoate C6H12O2 29.39 0.1847 Hexane C6H14 24.97 0.1753 2,3-Dimethylbutane C6H14 23.29 0.166 1-Hexanol C6H14O 31.35 0.1829 Triethylamine C6H15N 27.59 0.1836 Dipropylamine C6H15N 24.82 0.1591 Benzonitrile C7H5N 33.89 0.1727 Benzaldehyde C7H6O 30.3 0.1553 Toluene C7H8 24.89 0.1499 o-Cresol C7H8O 28.33 0.1447 m-Cresol C7H8O 31.86 0.1609 p-Cresol C7H8O 28.11 0.1422 Benzyl alcohol C7H8O 34.7 0.173 Anisole C7H8O 28.6 0.1579 Heptane C7H16 30.89 0.2038 Heptanol C7H15OH 37.22 0.2097 Ethylbenzene C8H10 30.86 0.1782 o-Xylene C8H10 31.06 0.1756 m-Xylene C8H10 31.41 0.1814 p-Xylene C8H10 31.54 0.1824 Phenetole C8H10O 35.7 0.1966 N,N-Dimethylaniline C8H11N 37.92 0.1967 Octane C8H18 37.86 0.2372 2,5-Dimethylhexane C8H18 35.49 0.2299 1-Octanol C8H18O 43.42 0.2371 Quinoline C9H7N 36.7 0.1672 Cumene C9H12 36.2 0.2044 Propylbenzene C9H12 37.14 0.2073 1,2,4-Trimethylbenzene C9H12 38.03 0.2088 Mesitylene C9H12 37.87 0.2118 Nonane C9H20 45.11 0.2702 1-Nonanol C9H20O 50 0.2654 Naphthalene C10H8 40.32 0.192 Butylbenzene C10H14 44.07 0.2378 Isobutylbenzene C10H14 40.4 0.2215 o-Cymene C10H14 42.7 0.234 p-Cymene C10H14 45.27 0.2478 p-Diethylbenzene C10H14 45.03 0.2439 1,2,4,5-Tetramethylbenzene C10H14 45.8 0.24 Decane C10H22 52.88 0.3051 1-Decanol C10H22O 57.45 0.2971 Undecane C11H24 60.88 0.3396 Biphenyl C12H10 47.16 0.213 Dodecane C12H26 69.14 0.3741 1-Dodecanol C12H26O 72.69 0.3598 Diphenylmethane C13H12 60.46 0.2798 Tridecane C13H28 77.94 0.4109 1-Tridecanol C13H28O 81.2 0.3942 1-Tetradecanol C14H30O 89.91 0.4289 Pentadecane C15H32 96.5 0.4857 * To convert a into atm L2/mol2 multiply by 0.986 atm/bar * To convert a into kPa L2/mol2 multiply by 100.0 kPa/bar

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