Contents
Key Stage 4
Meaning
The relative formula mass (Mr) of a molecule is the mass of one mole of molecules.
NB One mole is 6.02x1023 molecules.
About Relative Formula Mass
- The relative formula mass is used to find the mass of a molecule needed to perform a complete reaction with another chemical.
Calculating Relative Formula Mass
- Relative formula mass can be calculated from the chemical formula of the molecule and the relative atomic mass of the elements.
Find the relative formula mass of O2. | Find the relative formula mass of CO2 | Find the relative formula mass of C6H12O6 |
Relative Atomic Mass of Oxygen = 16g Mr of O2 = 16x2 Mr = 32g |
Relative Atomic Mass of Carbon = 12g Relative Atomic Mass of Oxygen = 16g Mr of CO2 = 12x1 + 16x2 Mr = 44g |
Relative Atomic Mass of Carbon = 12g Relative Atomic Mass of Hydrogen = 1g Relative Atomic Mass of Oxygen = 16g Mr of C6H12O6 = 12x6 + 1x12 + 16x6 Mr = 180g |
References
AQA
- Relative formula mass (Mr), pages 64-5, GCSE Chemistry, Hodder, AQA
- Relative formula mass, M, page 123, GCSE Combined Science; The Revision Guide, CGP, AQA
- Relative formula mass, M, pages 41-48, GCSE Chemistry; The Revision Guide, CGP, AQA
- Relative formula mass, pages 100-1, 106-8, 115-7, 120-3, 125, 167, GCSE Chemistry; Student Book, Collins, AQA
- Relative formula mass, pages 104-108, 114-117, GCSE Combined Science Trilogy; Chemistry, CGP, AQA
- Relative formula mass, pages 110-114, 120-124, GCSE Chemistry, CGP, AQA
- Relative formula mass, pages 177-8, GCSE Combined Science Trilogy 1, Hodder, AQA
- Relative formula mass, pages 62-63, GCSE Chemistry; Third Edition, Oxford University Press, AQA