M

Molar Mass

M = m/n; SI: g/mol; e.g., H₂O: 18.015 g/mol
Quick Reference
Formula / NotationM = m/n; SI: g/mol; e.g., H₂O: 18.015 g/mol
Also Known AsMolecular weight (loosely), formula weight, M (molar mass), gram-molecular weight

What is Molar Mass?

The mass of one mole of a substance, expressed in g/mol. Numerically equal to the atomic or molecular mass in atomic mass units (amu). Molar mass is used to convert between grams and moles and is essential for stoichiometric calculations.

Formula & Notation

M = m/n; SI: g/mol; e.g., H₂O: 18.015 g/mol

Other Names / Synonyms: Molecular weight (loosely), formula weight, M (molar mass), gram-molecular weight

Properties & Characteristics

Molar mass (M) is the mass of one mole of a substance, numerically equal to its relative molecular (or formula) mass expressed in g/mol. It is calculated as the sum of atomic masses of all atoms in one formula unit. Molar mass is used to convert between mass and moles: n = m/M. Exact molar masses are determined from high-resolution mass spectrometry; average molar masses use IUPAC atomic weight averages (which account for natural isotopic abundances).

Uses & Applications

Molar mass is fundamental to: stoichiometric calculations (n = m/M), preparing molar solutions, converting between mass and amount of substance in all quantitative analytical work, and in determining molecular formulas from empirical formula and molar mass data (from MS, osmometry, or cryoscopy).

Safety Information

No direct safety concern. Molar mass calculation errors propagate into wrong amounts of reagents being weighed — a critical quality and safety issue in pharmaceutical manufacturing, where exact dosage depends on correct molar mass used in formulation calculations.

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

Key Facts

Term Molar Mass
Formula M = m/n; SI: g/mol; e.g., H₂O: 18.015 g/mol
Synonyms Molecular weight (loosely), formula weight, M (molar mass), gram-molecular weight

Frequently Asked Questions

The mass of one mole of a substance, expressed in g/mol. Numerically equal to the atomic or molecular mass in atomic mass units (amu). Molar mass is used to convert between grams and moles and is essential for stoichiometric calculations.

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