Final answer:
The molecular formula of a compound with a mass of 56 g and an empirical formula of CH2 is C4H8. This is determined by dividing the mass of the compound by the molar mass of the empirical formula, yielding approximately 4, so the empirical units are multiplied by 4.
Step-by-step explanation:
The molecular formula of a compound is the actual number of atoms of each element in a compound. The empirical formula CH2 indicates the simplest whole number ratio of carbon to hydrogen atoms in the compound. Given the mass of the compound is 56 g, one must first determine the molar mass of the empirical formula CH2.
The molar mass of CH2 is 12.01 g/mol for carbon plus 2 x 1.01 g/mol for hydrogen, which equals 14.03 g/mol. To find how many empirical units are in the molecular formula, divide the given molecular mass (56 g) by the empirical formula mass (14.03 g/mol):
56 g / 14.03 g/mol = 3.99 ≈ 4
Therefore, the molecular formula is four times the empirical formula, which would be (CH2)4: C4H8. Thus, C4H8 is the molecular formula of the compound.