# State what is meant by the term 'relative molecular mass' and explain how the relative molecular mass of sulfuric acid, H₂SO₄, is obtained from the relative atomic masses of its constituent elements.

> Cambridge International IGCSE Chemistry (0620) — 3.2 Relative masses of atoms and molecules · State and Explain · 4 marks

## Mark scheme (4 marks)

1. Relative molecular mass is the mass of a molecule compared to one-twelfth of the mass of a carbon-12 atom (or: the average mass of a molecule on a scale where carbon-12 = 12)
2. Relative molecular mass is found by adding together the relative atomic masses of all atoms present in the molecule
3. Correct identification and use of the number of each type of atom in H₂SO₄: 2 hydrogen atoms, 1 sulfur atom, 4 oxygen atoms
4. Correct calculation shown: (2 × 1) + (1 × 32) + (4 × 16) = 98, giving a relative molecular mass of 98

## Key terms

- [relative molecular mass](https://www.gradenine.co.uk/glossary/relative-molecular-mass)
- [relative atomic mass](https://www.gradenine.co.uk/glossary/relative-atomic-mass)

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "State and Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/state-what-is-meant-by-the-98b025aa) · Published by Druglandscape Ltd.