Final answer:
An empirical formula shows the simplest ratio of elements in a compound, while a molecular formula gives the exact number of atoms of each element in the molecule.
To find a molecular formula, divide the compound's molecular mass by the empirical formula mass and multiply the empirical formula by this factor (n).
Step-by-step explanation:
The empirical formula of a compound represents the simplest whole-number ratio of the elements that compose that compound. For example, glucose has a molecular formula of C6H12O6, but since these numbers can all be divided by 6, its empirical formula is CH2O.
The empirical formula gives us the relative numbers of atoms of each element in a compound, but not necessarily the actual numbers present in a molecule of that compound.
The molecular formula, on the other hand, provides the exact number of each type of atom in a molecule. To derive a molecular formula, one must know the compound's molecular or molar mass and the empirical formula mass.
By dividing the molecular or molar mass by the empirical formula mass, we can obtain the number of empirical formula units per molecule (n), allowing us to determine the molecular formula. For instance, if n is found to be 2 and the empirical formula is CH2O, then the molecular formula would be C2H4O2.
It's important to note that some compounds have the same empirical and molecular formulas, such as H2O or P2O5, where no simpler whole-number ratio can be made.
However, for compounds like glucose, where the simplicity of the empirical formula differs from the complexity of the molecular formula, understanding how to convert between these two representations becomes crucial to understanding the substance's chemistry.