What is the main application of using percent composition in chemistry?

Using percent composition in chemistry is primarily applied to understand the distribution of elements in a compound. Percent composition provides the percentage by mass of each element within a compound. This information is crucial for chemists as it helps reveal the empirical formula and the molecular structure of compounds, which in turn aids in understanding the compound's properties and behaviors.

For instance, knowing the percent composition can help to determine the ratios of different elements in a compound, which is essential for stoichiometric calculations in chemical reactions. It also allows chemists to compare the composition of different samples or to deduce the identity of an unknown compound based on its composition.

The other options focus on aspects that are not directly related to the primary application of percent composition. For instance, boiling point, mass of the compound, and categorization based on reactivity involve other measurements and considerations that aren't central to understanding elemental distribution within a compound.