Final answer:
The molecular formula always consists of whole numbers and represents the actual number of atoms of each element in a molecule. The empirical formula is the simplest whole-number ratio of these elements, and the molecular formula can sometimes be a multiple of the empirical formula, as seen in the example of glucose (C6H12O6) and its empirical formula (CH2O).
Step-by-step explanation:
The molecular formula represents the actual number of atoms of each element in a compound, and these numbers are always whole numbers.
However, the molecular formula can sometimes be a multiple of the empirical formula, which shows the simplest whole-number ratio of the elements in a compound. For instance, the molecular formula for glucose is C6H12O6, which indicates that there are 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms in a molecule of glucose.
The empirical formula for glucose, which is CH2O, also represents whole numbers of atoms, but shows this ratio in the simplest form. To determine the molecular formula from the empirical formula, you must know the compound's molar mass.
Let's solve an example problem. A molecule of metaldehyde contains 8 carbon atoms, 16 hydrogen atoms, and 4 oxygen atoms, thus its molecular formula is C8H16O4. The empirical formula is determined by finding the simplest whole-number ratio of the atoms, which in this case is C2H4O, since the 8:16:4 ratio can be simplified to 2:4:1.