E

Empirical Formula Mass

EFM = sum of atomic masses in empirical formula (g/mol)
Quick Reference
Formula / NotationEFM = sum of atomic masses in empirical formula (g/mol)
Also Known AsEmpirical formula weight, formula unit mass, relative empirical formula mass

What is Empirical Formula Mass?

The sum of the atomic masses of all atoms in the empirical formula of a compound. Comparing the empirical formula mass to the molar mass of the compound allows calculation of the molecular formula. For example, CH₂O has an empirical formula mass of 30 g/mol.

Formula & Notation

EFM = sum of atomic masses in empirical formula (g/mol)

Other Names / Synonyms: Empirical formula weight, formula unit mass, relative empirical formula mass

Properties & Characteristics

The empirical formula mass is the sum of the atomic masses of all atoms in the empirical formula of a compound. For ionic compounds and empirical formula compounds, the empirical formula mass equals the formula mass (or formula unit mass). For molecular compounds, the molar mass is a whole-number multiple of the empirical formula mass (molar mass = n × empirical formula mass). This relationship is used to determine the molecular formula from empirical formula and molar mass data.

Uses & Applications

Calculating empirical formula mass is a standard step in converting elemental analysis data to molecular formula. Combined with molar mass (from mass spectrometry, cryoscopy, or osmometry), the ratio gives the multiplier n to convert empirical to molecular formula.

Safety Information

No direct safety concern. Calculation errors in empirical formula mass can lead to incorrect molecular formula assignment, potentially causing confusion in pharmaceutical synthesis or hazardous material identification.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Empirical Formula Mass
Formula EFM = sum of atomic masses in empirical formula (g/mol)
Synonyms Empirical formula weight, formula unit mass, relative empirical formula mass

Frequently Asked Questions

The sum of the atomic masses of all atoms in the empirical formula of a compound. Comparing the empirical formula mass to the molar mass of the compound allows calculation of the molecular formula. For example, CH₂O has an empirical formula mass of 30 g/mol.

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