What is the percent by mass of carbon in C3H8?

The chemical name for molecular formula C3H8 is propane. Propane has a weight of 44.10 grams per mole. Carbon (C) has a weight of 12.01 grams per mole. 1 mole of propane contains 3 moles of carbon. Therefore 81.70 percent by mass of propane is C.