As a sample of propane C3H3 contains 14.8 moles of carbon atoms. How many totals moles of atoms does the sample contains?

Answer 1

You made a typo. Propane is C3H8 (not C3H3). If it contains 14.8 moles C atoms, it must contain 14.8 x (8/3) moles H atoms. Another way to look at it is that if you had 14.3 moles C atoms, you must have had 14.3/3 moles C3H8 molecules (whatever that number is), then you had 8 times that value of H atoms.