Non-ideal gas - Van der Waal's Equation and Constants
The 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 | b L/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