Avogadro's number
represents the number of units in one mole of any substance. This has the value
of 6.022 x 10^23 units / mole. This number can be used to convert the number of
atoms or molecules into number of moles.
2.5 mol CO2 ( 2 mol O / 1 mol CO2 ) ( 6.022 x 10^23 atom / mole ) = 3.011 x 10^24 atoms of oxygen