Percent Composition
Definition
Percent composition is the percentage by mass of each element in a compound. It indicates how much of the compound’s total mass is contributed by each individual element. This is a crucial concept in chemistry used to analyze the makeup of substances.
Mathematical Formula
The percent composition of an element is calculated using the formula:
Percent Composition = (Mass of Element / Molar Mass of Compound) × 100%
This formula is applied to each element in the compound to determine their respective mass percentages.
Example
Consider water (H2O):
- Mass of 2 H atoms = 2 × 1.01 = 2.02 g
- Mass of 1 O atom = 16.00 g
- Molar mass of H2O = 18.02 g/mol
Percent composition of Hydrogen = (2.02 / 18.02) × 100% ≈ 11.2%
Percent composition of Oxygen = (16.00 / 18.02) × 100% ≈ 88.8%
Importance and Uses
- Identifying unknown compounds in chemical analysis.
- Verifying purity of a substance in quality control.
- Preparing chemical solutions with accurate proportions.
- Determining empirical and molecular formulas of compounds.