And what is the "empirical formula"...? It is the simplest WHOLE NUMBER ratio defining constituent atoms in a species. And thus the "empirical formula" for CH_4, C_2H_6, and C_3H_8, are CH_4, CH_3, and C_3H_8 respectively...With me? Combustion analysis of organic compounds is nowadays routine...."% by mass" with respect to carbon, hydrogen, nitrogen, may be readily acquired...and this allows determination of the empirical formula..
And then some determination of molecular mass is obtained…the "molecular formula" is a whole number MULTIPLE of the "empirical formula..."...i.e.
"molecular formula"-=nxx"empirical formula"
And of course n "MAY EQUAL" 1..
See here for a representative problem....
