# Explain how the molecular formula of a compound can be determined from its empirical formula and its molar mass, using the example of a compound with the empirical formula CH₂O and a molar mass of 180 g mol⁻¹.

> IB DP Chemistry Standard Level (2023 syllabus) — S1.4 Counting particles by mass: The mole · Explain · 4 marks

## Mark scheme (4 marks)

1. Calculate the empirical formula mass of CH₂O as 30 g mol⁻¹
2. Divide the molar mass by the empirical formula mass to obtain the whole-number ratio (n = 180 ÷ 30 = 6)
3. Multiply all subscripts in the empirical formula by n to give the molecular formula
4. The molecular formula is C₆H₁₂O₆

## Key terms

- [empirical formula](https://www.gradenine.co.uk/glossary/empirical-formula)
- [molecular formula](https://www.gradenine.co.uk/glossary/molecular-formula)
- [molar mass](https://www.gradenine.co.uk/glossary/molar-mass)

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-molecular-formula-of-2cac3941) · Published by Druglandscape Ltd.