Ace Your AP Chemistry Journey 2026 – Unleash the Elements and Score Big!

The calculation of percent composition of an element in a compound involves determining the proportion of that element's mass relative to the total mass of the compound. The correct formula used in this calculation is (mass of element in 1 mole of compound / molar mass of the compound) x 100%. This expression precisely quantifies how much of the total molar mass of the substance is attributed to the specific element in question, converting that ratio into a percentage.

By calculating the mass of the element present in one mole of the compound, you obtain a basis for understanding how significant that element is within the entire molecular structure. The molar mass of the compound represents the total mass of one mole of that compound, providing the necessary context to gauge how much of that total mass is contributed by the element of interest.

The remaining answer choices don't accurately reflect the relationship needed for calculating percent composition. For instance, simply dividing the mass of the element by the total mass of the compound does not account for the fact that we're often working with the per mole basis in chemistry (as indicated in the correct answer), and neither does it provide a conversion to a percentage. Similarly, options involving total volume of a solution or mistakenly manipulating the molar mass relative to the mass of