Final answer:
B. C2H5OH has a molecular formula of C2H6O, which is already in the simplest whole-number ratio and cannot be simplified further. Therefore, its molecular formula is the same as its empirical formula.
Step-by-step explanation:
The question asks which molecule has the same empirical formula as its molecular formula. The empirical formula represents the simplest whole-number ratio of elements in a compound, while the molecular formula represents the actual number of atoms of each element in a molecule of the compound.
Let's analyze the options given:
A. CH3COOH - The molecular formula is C2H4O2, and the empirical formula, obtained by reducing the ratio to the simplest form, is CH2O.
B. C2H5OH - The molecular formula is C2H6O, which is already in the simplest whole-number ratio.
C. C2H4 - The molecular formula is C2H4 and it cannot be simplified further, so it is the same as the empirical formula.
D. C4H10 - The molecular formula is C4H10, which simplifies to the empirical formula C2H5.
Therefore, the correct answer is B. C2H5OH, since its molecular formula, C2H6O, cannot be reduced to a simpler whole-number ratio and is thus the same as its empirical formula.