# Explain what is meant by the term 'mole' and describe how the molar mass of a substance is used to find the number of moles in a given mass of that substance.

> AQA A-Level Chemistry (7405) — 3.1.2 Amount of substance · Explain · 5 marks

## Mark scheme (5 marks)

1. A mole is the amount of substance that contains the same number of particles as there are atoms in 12 g of carbon-12 (Avogadro's number / 6.02 × 10²³ particles)
2. Molar mass is the mass of one mole of a substance / has units of g/mol
3. The molar mass is found by adding together the relative atomic masses (Ar) of all atoms in the formula
4. Number of moles = mass ÷ molar mass (correct relationship stated in words or symbols)
5. Correct worked application: e.g. a larger molar mass means fewer moles for the same mass / dividing a given mass by a larger molar mass gives a smaller number of moles (or equivalent correct statement showing understanding of the relationship)

## Key terms

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

## Related

- [Revision notes for AQA A-Level Chemistry (7405)](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-what-is-meant-by-the-85a75b29) · Published by Druglandscape Ltd.