What is the mass of carbon found in 350 grams of C2H6?

350 g C2H6 x 1 mole C2H6/30 g x 2 moles C/mole C2H6 x 12 g/mole C = 280 g carbonDone another way:

%C = 24/30 (x100%) = 80%

0.8 x 350 g = 280 grams carbon