How many grams of Cl are in a 38.0-g sample of the chlorofluorocarbon C2F3Cl3?

CF3Cl = 1 Carbon + 3 Fluorine + 1 Chlorine

[1 x (12.011 grams/mol)] + [3 x (18.988 grams/mol)] + [1 x (35.453 grams/mol)] = 104.428 grams/mol

38.0 grams x (1 mol /104.428 grams) = 0.364 moles CF3Cl

0.364 moles CF3Cl x (1 mole Cl / 1 mole CFCl3) = 0.364 moles Cl

Chlorine = 35.453 grams/mole

0.364 moles x (35.453 grams / 1 mole) = 12.9 grams of chlorine in 38.0 grams of CF3Cl