Question: what is an empirical formula for a hydrocarbon?
Answer: Add up the atomic masses of the atoms in the empirical formula. For example, the empirical formula of a hydrocarbon is CH 2 and its M r is 42. the mass of the atoms in the empirical formula is 14. 42 ÷ 14 = 3. so you need to multiply the numbers in the empirical formula by 3.