The molar mass of pentane is about 72.15 grams per mole. The molar mass of a compound or element is found by adding together the atomic weight of each atom that it contains.
Pentane, represented by the molecular formula C5H12, contains five atoms of carbon and 12 atoms of hydrogen. Since the atomic weight of carbon is about 12.01, the total mass of carbon in pentane is 60.05 grams per mole, differing slightly depending on rounding. Each atom of hydrogen has a mass of about 1.01 which gives a total mass of about 12.12 grams per mole for 12 atoms of hydrogen. When accounting for rounding differences, the two values add together to total about 72.15 grams per mole for each molecule of pentane.