Percent Composition Calculator
Find the percent by mass of each element in a chemical formula.
Composition by mass
C 40.00% · H 6.71% · O 53.28%
- Molar mass
- 180.156 g/mol
- Carbon (C)
- 40.0020%
- Hydrogen (H)
- 6.7142%
- Oxygen (O)
- 53.2838%
Show the work
Mass of each element in one formula unit
atoms × atomic weight
C: 6 × 12.011; H: 12 × 1.008; O: 6 × 15.999 = 72.066 + 12.096 + 95.994
Add them for the molar mass
M = Σ atoms × atomic weight
72.066 + 12.096 + 95.994 = 180.156 g/mol
Each element's share of the molar mass
% = element's mass ÷ M × 100
C: 72.066 ÷ 180.156 × 100; H: 12.096 ÷ 180.156 × 100; O: 95.994 ÷ 180.156 × 100 = C 40.00% · H 6.71% · O 53.28%
How it works
Mass % of an element = (atoms × atomic weight) ÷ molar mass × 100
Questions
- How does the percent composition calculator work?
- Mass % of an element = (atoms × atomic weight) ÷ molar mass × 100.
- What do I need to enter?
- Chemical formula. Optional fields can be left blank.
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