Final answer:
Percent composition is critical in identifying an unknown compound as it reveals the elemental makeup by mass, allowing for the determination or confirmation of the compound's molecular formula.
Step-by-step explanation:
Knowing the percent composition by mass of an unknown compound can indeed assist in identifying the compound's identity. Chemists utilize percent composition to understand what elements are present in a compound and their respective percentages. Simply put, the percent composition is the percent by mass of each element in a compound. The process involves dividing the mass of each element by the mass of the compound and then multiplying by 100% to convert this ratio into a percentage.
Consider a compound that is composed solely of carbon and hydrogen. If we measure the mass of carbon and hydrogen separately, we can use these values to determine the percent composition. For instance, if we have a 100-gram sample of a compound containing 85 grams of carbon and 15 grams of hydrogen, the percent composition would be 85% carbon and 15% hydrogen. This percentage reveals the proportional amounts of each element and can be crucial for deducing the molecular formula of the compound.
The percent composition of a compound can also be derived from its chemical formula. The subscripts in the formula indicate the number of atoms of each element and, together with the atomic masses of the elements, are used to calculate the mass percentage of each element. This method is especially useful when confirming the identity of a compound when its formula is already hypothesized.