Percent Composition Calculator
Calculate the mass percentage of each element in a chemical compound
Calculate Percent Composition
Enter the molecular formula (e.g., H2SO4, CaCO3, C6H12O6)
Formula Format Examples
• Water: H2O
• Sulfuric Acid: H2SO4
• Glucose: C6H12O6
• Sodium Chloride: NaCl
Percent Composition Results
Element Analysis
| Element | Symbol | Count | Atomic Mass | Total Mass | Percentage |
|---|---|---|---|---|---|
| Hydrogen | H | 2 | 1.008 | 2.016 g/mol | 2.06% |
| Oxygen | O | 4 | 15.999 | 63.996 g/mol | 65.25% |
| Sulfur | S | 1 | 32.060 | 32.060 g/mol | 32.69% |
Mass Percentage Breakdown
Calculation Steps
Percent Composition Formula
Example: Sulfuric Acid (H₂SO₄)
Given Information
Molecular Formula: H₂SO₄
Elements: H (2 atoms), S (1 atom), O (4 atoms)
Atomic Masses: H = 1.008, S = 32.06, O = 15.999
Step-by-Step Calculation
1. Element masses:
H: 2 × 1.008 = 2.016 g/mol
S: 1 × 32.06 = 32.06 g/mol
O: 4 × 15.999 = 63.996 g/mol
2. Molecular weight: 2.016 + 32.06 + 63.996 = 98.072 g/mol
3. Percentages:
H: (2.016 ÷ 98.072) × 100 = 2.06%
S: (32.06 ÷ 98.072) × 100 = 32.69%
O: (63.996 ÷ 98.072) × 100 = 65.25%
Common Element Masses
Calculation Tips
Always use accurate atomic masses from periodic table
Double-check molecular formula parsing
Verify percentages sum to 100%
Use significant figures appropriately
Applications
Understanding Percent Composition
What is Percent Composition?
Percent composition expresses the mass of each element in a compound as a percentage of the total mass. It tells us what fraction of a compound's mass comes from each constituent element, which is crucial for chemical analysis and stoichiometric calculations.
Key Concepts:
- • Mass percentage: (Element mass / Total mass) × 100
- • Molecular weight: Sum of atomic masses
- • Element mass: Atomic mass × number of atoms
- • Conservation: All percentages sum to 100%
Calculation Process
Step 1: Determine Molecular Weight
Calculate the total mass of one mole of the compound using atomic masses.
Step 2: Calculate Element Masses
Multiply atomic mass by the number of atoms of each element.
Step 3: Apply Formula
Divide element mass by molecular weight and multiply by 100.
Applications and Importance
Chemical Analysis
Determine the composition of unknown compounds and verify purity.
Stoichiometry
Calculate reactant and product quantities in chemical reactions.
Quality Control
Ensure pharmaceutical and industrial products meet specifications.
Environmental Analysis
Analyze pollutants and contaminants in environmental samples.
Materials Science
Characterize alloys, ceramics, and composite materials.
Nutritional Analysis
Determine elemental content in food and supplements.
Common Mistakes and Tips
Common Mistakes
• Using incorrect atomic masses
• Miscounting atoms in molecular formula
• Forgetting to multiply by 100 for percentage
• Not checking if percentages sum to 100%
• Rounding errors in intermediate calculations
Best Practices
• Use precise atomic masses from periodic table
• Double-check molecular formula parsing
• Keep extra decimal places in intermediate steps
• Verify final percentages sum to ~100%
• Round final answers to appropriate significant figures