The empirical formula provides the simplest whole number ratio of elements present in a compound, but it does not distinguish between different compounds that have the same ratio. In this case, both propane (C3H8) and butene (C4H8) have the same empirical formula, CH2.

Therefore, the empirical formula alone cannot be used to tell the difference between propane and butene. Additional information, such as molecular weight or structural information, would be necessary to distinguish between these two compounds.