So rubbing alcohol contains 60 % carbon, 13.4 % hydrogen and 26.6 % oxygen, the difference.
Now we have to convert % to atoms ( or mole) To do this we divide by the relative atomic mass.
C = 60/12 = 5
H = 13.4/1 = 13.4
O = 26.6/16 = 1.66
This is your empirical formula. However it doesn't really make sense having decimal points.
So divide by 1.66
C = 5/1.66 = 3.01
H = 13.4/ 1.66 = 8.07
O = 1.66/1.66 = 1
This makes more sense. C3H8O, the empirical formula.
