Molecular formula

What does a molecular formula show?

A molecular formula specifies the precise number of each type of atom present in a single molecule of a compound. For example, the molecular formula of water is H₂O, indicating two hydrogen atoms and one oxygen atom per molecule. Unlike empirical formulas, which show the simplest whole-number ratio of atoms, molecular formulas provide the actual molecular composition, enabling accurate determination of molar mass and reaction stoichiometry.

How is it different from other formula types?

While empirical formulas give the simplest ratio of elements (e.g., CH₂O for glucose), molecular formulas reflect the true molecular structure. For instance, hydrogen peroxide has an empirical formula of HO but a molecular formula of H₂O₂. Molecular formulas are crucial in regulatory contexts such as REACH, ISO, and USP, where precise chemical identity is required for safety, quality control, and compliance. They are also essential in analytical methods like GC-MS, HPLC, and NMR to confirm compound identity and purity.

Why is it important in chemical procurement and lab work?

In B2B procurement, molecular formulas ensure accurate sourcing and specification of chemicals, preventing substitution errors. In laboratories, they are foundational for synthesising compounds, preparing solutions, and interpreting spectroscopic data. Regulatory bodies such as the ECHA and FDA require molecular formulas in safety data sheets (SDS), certificates of analysis (CoA), and product specifications to ensure traceability and compliance.

Related concepts

Molecular formulas are closely linked to structural formulas, molecular weight, and IUPAC nomenclature. They are also used in conjunction with analytical techniques like mass spectrometry and elemental analysis to verify compound identity.