This worked example problem shows how to convert the number grams of a molecule to the number of moles of the molecule.
Determine the number of moles of CO2 in 454 grams of CO2.
First, look up the atomic masses for carbon and oxygen from the Periodic Table. The atomic mass of C is 12.01 and the atomic mass of O is 16.00. The formula mass of CO2 is:
12.01 + 2(16.00) = 44.01
Thus, one mole of CO2 weighs 44.01 grams. This relation provides a conversion factor to go from grams to moles. Using the factor 1 mol/44.01 g:
moles CO2 = 454 g x 1 mol/44.01 g = 10.3 moles
There are 10.3 moles CO2 in 454 grams of CO2