What is percent composition?
Percent composition tells you what percentage of a compound's total mass is contributed by each element. It's calculated as:
% of Element = (Mass of element in formula / Molar mass) × 100
Example: In H₂O, hydrogen = (2 × 1.008) / 18.015 × 100 = 11.19%, oxygen = 15.999 / 18.015 × 100 = 88.81%.