Question: how many moles of hydrogen are in mole of c2h6?
Answer: Well, since we know that there are 6 moles of hydrogen per 1 mole of C2H6, we can set up the dimensional analysis as such: 2 moles C2H6 x (6 moles hydrogen/1 mole C2H6) = ? Notice how the "moles of C2H6" can cancel, giving you your answer: 12 moles of hydrogen.