Equation and purpose
Mass fraction of an element in a compound.
\[\%E = \frac{m_E}{m_{tot}} \times 100\]
Mass fraction of an element in a compound.
REARRANGEMENTS
$m_E = \%E·m_{tot}/100$
Dimensional check: %
Variables and units
| Symbol | Quantity | Unit | Notes |
|---|---|---|---|
| %E | %E | — | — |
| m_E | m_E | — | — |
| m_{tot} | m_{tot} | — | — |
Conditions and limitations
Based on formula; total mass is sum of components.
Worked example
H₂O: %O =16.00/18.02×100=88.8%.
Percent Composition
Mass fraction of an element in a compound.
Equation
Inline: $%E = \frac{m_E}{m_{tot}} \times 100$$
Variables
| Symbol | Quantity | Unit | Notes |
|---|---|---|---|
| percent of element | % | — | |
| mass of element in sample | g | — | |
| total mass | g | — |
Conditions and limitations
Based on formula; total mass is sum of components.
Rearrangements
Dimensional check: %
Worked example
H₂O: %O =16.00/18.02×100=88.8%.
Steps: write equation → substitute with units → check dimensional consistency → report with correct significant figures.
Common errors
- Using moles instead of mass
- Counting atoms not mass
Related resources
- mole-stoichiometry topic
- Calculators — linked only when a real calculator implements this formula.
- Constants — sourced constants with version when values are required.
Sources
- NIST Physical Constants 2022 — CODATA.
Reviewed 2026-08-21 by Editorial Team; due 2027-08-21.
Common errors
- Using moles instead of mass
- Counting atoms not mass
RELATED FORMULAS
C
Chemistry Fundamentals Editorial TeamAuthor
E
Editorial Review BoardReviewer
Editorial Team — transparent review placeholder
Reviewed August 21, 2026
SOURCES
- [nist-2022]NIST Physical Constants 2022 (2022). NISThttps://physics.nist.gov/constants