# Molar mass

Molar mass is a physical property defined as the mass of a given substance divided by the amount of substance. The base SI unit for molar mass is kg/mol. However, for historical reasons, molar masses are almost always expressed in g/mol. The molar mass of a substance is the total weight of that substance (in kg or g) for one mole of that substance. That is, the weight of a substance for 6.022140857E23 molecules (Avogadro constant) of that substance.

Symbol
$M_{mol}$
Unit
g/mol
Formulae
$N_{A} m_{mol}$
Related
$m_{mol}$
Used in
$R_{gas}$
Choices
GasFormulaMmol
Air-28.9647
N2N228.013
SF6SF6146.055
CO2CO244.01
COCO28.01
O2O231.999
H2H22.016
NH3NH317.031
SO2SO264.064
HeHe4.003
ArAr39.948
KrKr83.798
XeXe131.293