Kaplan Nursing Entrance Practice Exam

What does the empirical formula of a chemical compound represent?

1. The detailed structure of the compound

2. The simplest positive integer ratio of atoms of each element

3. The total number of atoms present in the compound

4. The molecular weight of the compound

The correct answer is: The simplest positive integer ratio of atoms of each element

The empirical formula of a chemical compound indicates the simplest positive integer ratio of the different atoms that make up the compound. It provides critical information about the proportion of each element relative to the others but does not describe the actual number of atoms or the structure of the molecule. For example, in the compound glucose, the molecular formula (C6H12O6) shows that there are 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms, but the empirical formula would simply present this as CH2O, indicating the simplest ratio of 1:2:1 for carbon, hydrogen, and oxygen. This representation is particularly useful in understanding the basic composition of a compound without getting into the complexity of its molecular structure or the total count of atoms, which might vary depending on the specific arrangement of those atoms within the molecule.