Molecular Weight of Substances

Definition and molecular weight (molar mass) of common substances. The molecular weight, also called molar mass (M), is the mass of 1 mole of a substance, given in grams. In the SI system the unit is kg/kmol, in the English system it is lb/lbmol, and in the cgs system it is g/mol. The molecular weight is represented by the same number in all unit systems.

Substance	Molecular Weight (kg/kmol) (g/mol) (lb/lbmol)
Acetylene, C2H2	26.038
Air	28.966
Ammonia (R-717)	17.02
Argon, Ar	39.948
Benzene	78.114
n - Butane, C4 H10	58.124
1,2 - Butadiene	54.092
1-Butene	56.108
cis -2-Butene	56.108
trans-2-Butene	56.108
Butylene	56.06
Carbon Dioxide, CO2	44.01
Carbon Disulphide	76.13
Carbon Monoxide, CO	28.011
Chlorine	70.906
Cyclohexane	84.162
Cyclopentane	70.135
n - Decane	142.286
Deuterium	2.014
2,3 - Dimetylbutane	86.178
2,2 - Dimethylpentane	100.205
Diisobutyl	114.232
Duoderane	170.21
Ethane, C2H6	30.07
Ethene	28.05
Ethyl Alcohol	46.07
Ethylbenzene	106.168
Ethyl Chloride	64.515
3 - Ethylpentane	100.205
Ethylene, C2H4	28.054
Fluorine	37.996
Helium, He	4.002602
n - Heptane	100.205
n - Hexane	86.178
Hydrochloric Acid	36.47
Hydrogen, H2	2.016
Hydrogen Chloride	36.461
Hydrogen Sulfide	34.076
Hydroxyl, OH	17.01
Isobutane (2-Metyl propane)	58.124
Isobutene	56.108
Isooctane	114.232
Isopentane	72.151
Isoprene	68.119
Isopropylbenzene	120.195
Krypton	83.8
Methane, CH4	16.043
Methyl Alcohol	32.04
Methyl Butane	72.15
Methyl Chloride	50.488
Methylcyclohexane	98.189
Methylcyclopentane	84.162
2 - Methylhexane	100.205
2 - Methylpentane	86.178
Natural Gas	19
Neon, Ne	20.179
Neohexane	86.178
Neopentane	72.151
Nitric Oxide, NO	30.006
Nitrogen, N2	28.0134
Nitrous Oxide, N2O	44.013
n - Nonane	128.259
n - Octane	114.232
Oxygen, O2	31.9988
Ozone	47.998
n - Pentane	72.151
Pentylene	70.08
Propane, C3 H8	44.097
Propene	42.081
Propylene	42.08
R-11	137.37
R-12	120.92
R-22	86.48
R-114	170.93
R-123	152.93
R-134a	102.03
R-611	60.05
Styrene	104.152
Sulfur	32.02
Sulfur Dioxide (Sulphur Dioxide)	64.06
Sulfuric Oxide	48.1
Toluene, toluol	92.141
Triptane	100.205
Xenon	131.3
o - Xylene, xylol	106.168
Water Vapor - Steam, H2O	18.02