Percent Composition

📖 What is Percent Composition?

Percent composition tells you what percentage by mass each element contributes to a compound. It is used to identify compounds, verify formulas, and calculate empirical formulas.

% element = (mass of element in 1 mol / molar mass of compound) × 100

🔤 What Each Part Means

mₑ

Mass of element (g/mol)Atomic mass × subscript of that element in the formula

M

Molar mass of compound (g/mol)Sum of all atomic masses in the formula

📝 Step-by-Step Example

Find the percent composition of water (H₂O). Atomic masses: H=1, O=16.

1

Calculate molar mass of H₂OM = 2(1) + 16 = 18 g/mol

2

% of Hydrogen% H = (2/18) × 100 = 11.11%

3

% of Oxygen% O = (16/18) × 100 = 88.89%

✓

Check: 11.11% + 88.89% = 100% ✓

🧮 Interactive Calculator

Element mass in compound (g/mol)

Molar mass of compound (g/mol)

Result will appear here

📖 What is Percent Composition?

🔤 What Each Part Means

📝 Step-by-Step Example

🧮 Interactive Calculator

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