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) = R T (1)
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 P V = n R T.
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/mol2multiply by 0.986 atm/bar. To convert a into kPa L2/mol2multiply 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 | NH4 Cl | 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 | ClH4 P | 4.111 | 0.04545 |
Chlorine | Cl2 | 6.343 | 0.05422 |
Trichlorofluorosilane | Cl3 FSi | 15.67 | 0.1273 |
Fluorine | F2 | 1.171 | 0.02896 |
Germanium tetrachloride | GeCl4 | 23.12 | 0.1489 |
Nitrogen trifluoride | F3 N | 3.58 | 0.05453 |
Phosphorus trifluoride | F3 P | 4.954 | 0.0651 |
Tetrafluorohydrazine | F4 N2 | 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 | CCl3 F | 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 | CH3 Cl | 7.566 | 0.06477 |
Fluoromethane | CH3F | 5.009 | 0.05617 |
Nitromethane | NH3 NO2 | 17.18 | 0.1041 |
Methane | CH4 | 2.3 | 0.04301 |
Methanol | CH3 OH | 9.472 | 0.06584 |
Methanethiol | CH3 SH | 8.911 | 0.06756 |
Methylamine | CH3 NH2 | 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 | C2H3 Cl3 | 20.15 | 0.1317 |
Fluroethylene | C2H3 F | 5.984 | 0.06504 |
1,1,1-Trifluoroethane | C2H3 F3 | 9.302 | 0.09572 |
Acetonitrile | C2H3 N | 17.89 | 0.1169 |
Ethylene | C2H4 | 4.612 | 0.05821 |
1,1-Dichloroethane | C2H4 Cl2 | 15.73 | 0.1072 |
1,2-Dichloroethane | C2H4 Cl2 | 17 | 0.108 |
Ethylene oxide | C2H4 O | 8.922 | 0.06779 |
Acetic acid | CH3 COOH | 17.71 | 0.1065 |
Methyl formate | C2H4 O2 | 11.54 | 0.08442 |
Bromoethane | C2H5 Br | 11.89 | 0.08406 |
Chloroethane | C2H5 Cl | 11.7 | 0.09 |
Fluoroethane | C2H5 F | 8.17 | 0.07758 |
Ethane | C2H6 | 5.57 | 0.06499 |
Dimethyl ether | C2H6 O | 8.69 | 0.07742 |
Ethanol | C2H5 OH | 12.56 | 0.0871 |
Dimethyl sulphide | C2H5 SH | 13.34 | 0.09453 |
Ethanethiol | C2H5 SH | 13.23 | 0.09447 |
Dimethylamine | C2H7 N | 10.44 | 0.0851 |
Ethylamine | C2H7 N | 10.79 | 0.08433 |
Perfluoropropane | C3 F8 | 12.96 | 0.1338 |
Propanenitrile | C3 H5 N | 21.57 | 0.1369 |
Propene | C3 H6 | 8.438 | 0.08242 |
Cyclopropane | C3 H6 | 8.293 | 0.0742 |
Acetone | C3 H6 O | 16.02 | 0.1124 |
Propanal | C3 H6 O | 14.08 | 0.09947 |
Ethyl formate | C3 H6 O2 | 15.91 | 0.1115 |
Methyl acetate | C3 H6 O2 | 15.75 | 0.1108 |
Propanoic acid | C3 H6 O2 | 23.49 | 0.1386 |
1-Chloropropane | C3 H7 Cl | 16.11 | 0.1141` |
Propane | C3 H8 | 9.385 | 0.09044 |
1-Propanol | C3 H8 O | 16.26 | 0.108 |
2-Propanol | C3 H8 O | 15.82 | 0.1109 |
Ethyl methyl ether | C3 H8 O | 12.7 | 0.1034 |
Ethyl methyl sulphide | C3 H8 S | 19.45 | 0.13 |
Propylamine | C3 H9 N | 15.26 | 0.1094 |
Trimethylamine | C3 H9 N | 13.37 | 0.1101 |
Furan | C4 H4 O | 12.74 | 0.0926 |
Thiophene | C4 H4 S | 17.21 | 0.1058 |
Pyrrole | C4 H4 N | 18.82 | 0.1049 |
1,3-Butadiene | C4 H6 | 12.17 | 0.102 |
Acetic anhydride | C4 H6 O3 | 26.8 | 0.157 |
Butanenitrile | C4 H7 N | 25.76 | 0.1568 |
1-Butene | C4 H8 | 12.76 | 0.1084 |
Cyclobutane | C4 H8 | 12.39 | 0.096 |
2-Butanone | C4 H8 O | 19.97 | 0.1326 |
Tetrahydrofuran | C4 H8 O | 16.39 | 0.1082 |
1,4-Dioxane | C4 H8 O2 | 19.29 | 0.1171 |
Ethyl acetate | C4 H8 O2 | 20.57 | 0.1401 |
Methyl propanoate | C4 H8 O2 | 20.51 | 0.1377 |
Propyl formate | C4 H8 O2 | 20.79 | 0.1377 |
Butanoic acid | C4 H8 O2 | 28.18 | 0.1609 |
Pyrrolidine | C4 H9 N | 16.84 | 0.1056 |
Butane | C4 H10 | 13.93 | 0.1168 |
Isobutane | C4 H10 | 13.36 | 0.1168 |
1-Butanol | C4 H10 O | 20.9 | 0.1323 |
2-Methyl-2-propanol | C4 H10 O | 18.81 | 0.1324 |
2-Methyl-1-propanol | C4 H10 O | 20.35 | 0.1324 |
Diethyl ether | C4 H10 O | 17.46 | 0.1333 |
Diethyl sulphide | C4 H10 S | 22.85 | 0.1462 |
Butylamine | C4 H11 N | 19.41 | 0.1301 |
Diethylamine | C4 H11 N | 19.4 | 0.1383 |
Tetramethylsilane | C4 H12 Si | 20.81 | 0.1653 |
Furfural | C5 H4 O2 | 22.23 | 0.1182 |
Pyridine | C5 H5 N | 19.77 | 0.1137 |
Cyclopentene | C5 H8 | 15.61 | 0.1097 |
1-Pentene | C5 H10 | 17.86 | 0.137 |
2-Methyl-1-butene | C5 H10 | 16.9 | 0.129 |
2-Methyl-2-butene | C5 H10 | 17.26 | 0.1279 |
Cyclopentane | C5 H10 | 16.94 | 0.118 |
Tetrahydropyran | C5 H10 O | 20.02 | 0.1247 |
Isobutyl formate | C5 H10 O2 | 22.82 | 0.1476 |
Propyl acetate | C5 H10 O2 | 26.23 | 0.17 |
Ethyl propanoate | C5 H10 O2 | 25.86 | 0.1688 |
Methyl butanoate | C5 H10 O2 | 25.83 | 0.1661 |
Methyl isobutanoate | C5 H10 O2 | 24.87 | 0.1639 |
Piperidine | C5 H11 N | 20.84 | 0.125 |
Pentane | C5 H12 | 19.13 | 0.1451 |
Isopentane | C5 H12 | 18.29 | 0.1415 |
Neopentane | C5 H12 | 17.17 | 0.141 |
1-Pentanol | C5 H12 O | 25.81 | 0.1564 |
Bromobenzene | C6 H5 Br | 28.96 | 0.1541 |
Chlorobenzene | C6 H5 Cl | 25.8 | 0.1454 |
Fluorobenzene | C6 H5 F | 20.1 | 0.1279 |
Iodobenzene | C6 H5 I | 33.54 | 0.1658 |
Benzene | C6 H6 | 18.82 | 0.1193 |
Phenol | C6 H5 OH | 22.93 | 0.1177 |
Aniline | C6 H5 NH2 | 29.14 | 0.1486 |
Cyclohexanone | C6 H10 O | 31.1 | 0.17 |
Hexanenitrile | C6 H11 N | 35.5 | 0.1996 |
Cyclohexane | C6 H12 | 21.95 | 0.1413 |
Cyclohexanol | C6 H11 OH | 28.93 | 0.1586 |
Pentyl formate | C6 H12 O2 | 27.97 | 0.173 |
Isobutyl acetate | C6 H12 O2 | 29.05 | 0.1845 |
Ethyl butanoate | C6 H12 O2 | 30.53 | 0.1922 |
Ethyl 2-methylpropanoate | C6 H12 O2 | 29.05 | 0.1872 |
Methyl pentanoate | C6 H12 O2 | 29.39 | 0.1847 |
Hexane | C6 H14 | 24.97 | 0.1753 |
2,3-Dimethylbutane | C6 H14 | 23.29 | 0.166 |
1-Hexanol | C6 H14 O | 31.35 | 0.1829 |
Triethylamine | C6 H15 N | 27.59 | 0.1836 |
Dipropylamine | C6 H15 N | 24.82 | 0.1591 |
Benzonitrile | C7 H5 N | 33.89 | 0.1727 |
Benzaldehyde | C7 H6 O | 30.3 | 0.1553 |
Toluene | C7 H8 | 24.89 | 0.1499 |
o-Cresol | C7 H8 O | 28.33 | 0.1447 |
m-Cresol | C7 H8 O | 31.86 | 0.1609 |
p-Cresol | C7 H8 O | 28.11 | 0.1422 |
Benzyl alcohol | C7 H8 O | 34.7 | 0.173 |
Anisole | C7 H8 O | 28.6 | 0.1579 |
Heptane | C7 H16 | 30.89 | 0.2038 |
Heptanol | C7 H15 OH | 37.22 | 0.2097 |
Ethylbenzene | C8 H10 | 30.86 | 0.1782 |
o-Xylene | C8 H10 | 31.06 | 0.1756 |
m-Xylene | C8 H10 | 31.41 | 0.1814 |
p-Xylene | C8 H10 | 31.54 | 0.1824 |
Phenetole | C8 H10 O | 35.7 | 0.1966 |
N,N-Dimethylaniline | C8 H11 N | 37.92 | 0.1967 |
Octane | C8 H18 | 37.86 | 0.2372 |
2,5-Dimethylhexane | C8 H18 | 35.49 | 0.2299 |
1-Octanol | C8 H18 O | 43.42 | 0.2371 |
Quinoline | C9 H7 N | 36.7 | 0.1672 |
Cumene | C9 H12 | 36.2 | 0.2044 |
Propylbenzene | C9 H12 | 37.14 | 0.2073 |
1,2,4-Trimethylbenzene | C9 H12 | 38.03 | 0.2088 |
Mesitylene | C9 H12 | 37.87 | 0.2118 |
Nonane | C9 H20 | 45.11 | 0.2702 |
1-Nonanol | C9 H20 O | 50 | 0.2654 |
Naphthalene | C10 H8 | 40.32 | 0.192 |
Butylbenzene | C10 H14 | 44.07 | 0.2378 |
Isobutylbenzene | C10 H14 | 40.4 | 0.2215 |
o-Cymene | C10 H14 | 42.7 | 0.234 |
p-Cymene | C10 H14 | 45.27 | 0.2478 |
p-Diethylbenzene | C10 H14 | 45.03 | 0.2439 |
1,2,4,5-Tetramethylbenzene | C10 H14 | 45.8 | 0.24 |
Decane | C10 H22 | 52.88 | 0.3051 |
1-Decanol | C10 H22 O | 57.45 | 0.2971 |
Undecane | C11 H24 | 60.88 | 0.3396 |
Biphenyl | C12 H10 | 47.16 | 0.213 |
Dodecane | C12 H26 | 69.14 | 0.3741 |
1-Dodecanol | C12 H26 O | 72.69 | 0.3598 |
Diphenylmethane | C13 H12 | 60.46 | 0.2798 |
Tridecane | C13 H28 | 77.94 | 0.4109 |
1-Tridecanol | C13 H28 O | 81.2 | 0.3942 |
1-Tetradecanol | C14 H30 O | 89.91 | 0.4289 |
Pentadecane | C15 H32 | 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