Flourotoluene contains 76.34% carbon,6.41% hydrogen, and 17.25 flourine Each mol of flourotoluene contains...?

Question

(cont-) one flourine atom. The total # of carbon, hydrogen, and flourine atoms in in one molecule of flourtoluene is ANSWERS: a) 8 b) 12 c) 13 d) 15 e) 14

Answer 1

The percent compositions mean that in 100 grams of the compound you'd have 76.34 grams C, 6.41 grams H and 17.25 grams F.

Convert each of these to moles by dividing by the atomic weight of each which gives:
6.36 mol C, 6.41 mol H and .907 mol F. Now divide each of these by .907 to get a ratio of C:H:F of 7:7:1. This is the mol ratio of each element, which is also the ratio of atoms. Since you have 7 C atoms and 7 H atoms for every F atom, answer (e) is the correct one.