# Explain what is meant by the term 'molar mass' and outline how the molar mass of a substance can be determined from the periodic table, using magnesium chloride, MgCl₂, as your example.

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

## Mark scheme (4 marks)

1. Molar mass is the mass of one mole of a substance
2. Molar mass has units of g mol⁻¹
3. The molar mass of an element is numerically equal to its relative atomic mass found on the periodic table
4. For MgCl₂, the molar mass is calculated by summing the relative atomic masses: Mg (24.31) + 2 × Cl (35.45) = approximately 95.2 g mol⁻¹

## Key terms

- [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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-what-is-meant-by-the-00ec0cd1) · Published by Druglandscape Ltd.