The molecular weight of a substance, also called the molar mass, M, is the mass of 1 mole of that substance, given in M gram.
In the SI system the unit of M is [kg/kmol] and in the English system the unit is [lb/lbmol], while in the cgs system the unit of M is [g/mol]. Molecular weight is represented by the same number in all unit systems regardless of the system used. For this reason, in many cases the unit for the molecular weight is not mentioned; however, one must realize that it is not a dimensionless parameter.
The molecular weight of a pure compound is determined from its chemical formula and the atomic weights of its elements. The atomic weights of the elements found in organic substances are C = 12.011, H = 1.008, S = 32.065, O = 15.999, and N = 14.007.
Example: The molecular weight of ethanol (C2H5OH)
To calculate the molecular weight of ethanol, the molecular weight of each atom in the molecule is summed:
Methanol = 2*12.011[kg/kmol] + 6*1.008[kg/kmol] + 1*15.999 [kg/kmol] = 46.069 [kg/kmol]
|n - Butane, C4H10||58.124|
|1,2 - Butadiene||54.092|
|Carbon Dioxide, CO2||44.01|
|Carbon Monoxide, CO||28.011|
|n - Decane||142.286|
|2,3 - Dimetylbutane||86.178|
|2,2 - Dimethylpentane||100.205|
|3 - Ethylpentane||100.205|
|n - Heptane||100.205|
|n - Hexane||86.178|
|Isobutane (2-Metyl propane)||58.124|
|2 - Methylhexane||100.205|
|2 - Methylpentane||86.178|
|Nitric Oxide, NO||30.006|
|Nitrous Oxide, N2O||44.013|
|n - Nonane||128.259|
|n - Octane||114.232|
|n - Pentane||72.151|
|Sulfur Dioxide (Sulphur Dioxide)||64.06|
|o - Xylene, xylol||106.168|
|Water Vapor - Steam, H2O||18.02|
Material properties of gases, fluids and solids - densities, specific heats, viscosities and more.
Chemical, physical and thermal properties of acetone, also called 2-propanone, dimethyl ketone and pyroacetic acid. Phase diagram included.
Dry air is a mixture of gases where the average molecular weight (or molar mass) can be calculated by adding the weight of each component.
Chemical, physical and thermal properties of benzene, also called benzol. Phase diagram included.
Chemical, physical and thermal properties of n-Butane.
Figures and table with changes in Prandtl number for carbon dioxide with changes in temperature and pressure.
Chemical, physical and thermal properties of carbon dioxide. Phase diagram included.
Isothermal and isentropic gas compression and expansion processes.
Chemical, physical and thermal properties of ethylene, also called ethene, acetene and olefiant gas. Phase diagram included.
Adiabatic flame temperatures for common fuel gases - propane, butane, acetylene and more - in air or oxygen atmospheres.
Densities and molecular weights of common gases like acetylene, air, methane, nitrogen, oxygen and others.
Flame and explosion limits for gases like propane, methane, butane, acetylene and more.
Molar specific heats for some common gases at constant volume.
Specific gravities of air, ammonia, butadiene, carbon dioxide, carbon monoxide and some other common gases.
Specific heat at constant volume, specific heat at constant pressure, specific heat ratio and individual gas constant - R - common gases as argon, air, ether, nitrogen and many more.
Calculate melting point of hydrocarbons from molecular weight (molar mass).
Vapor pressure vs. temperature for propane, n-butane, n-heptane and n-pentane hydrocarbons.
Chemical, Physical and Thermal Properties of Hydrogen - H2.
Chemical, Physical and Thermal Properties of Methane - CH4. Phase diagram included.
Mole fraction of water vapor is the ratio of water molecules to air and water molecules.
The mole is the SI base unit for an amount of a substance.
How to calculate total pressure and partial pressures for gas mixtures from Ideal Gas Law.
An introduction to vapor and steam.