C3H2N tells you the lowest possible whole number ratio of atoms in that molecule. That EMPIRICAL FORMULA must have the same ratio as the actual, MOLECULAR FORMULA. The empirical mass and molecular mass must share the same ratio as the formulas do, so find the mass of C3H2N: 3(12g)+2(1g)+14g=52g and compare that to the molecular weight of 260g. MFEF=MWEWsoMFEF=260g52g=5the actual formula is five times heavier than the empirical formula, so take the empirical formula and multiply each subscript by 5. That's why it works