GCSEChemistryEdexcelRevision Notes1. Atomic StructureCalculations Involving MassesRelative Formula Mass

Relative Formula Mass (Edexcel GCSE Chemistry): Revision Note

Exam code: 1CH0

Stewart Hird

Written by: Stewart Hird

Reviewed by: Caroline Carroll

Updated on

Edexcel ChemistryEdexcel Combined Science: Chemistry

Relative Formula Mass

  • We have seen previously that the symbol for the relative atomic mass is Ar

  • This is calculated from the mass number and relative abundances of all the isotopes of a particular element

  • The symbol for the relative formula mass is Mr and it refers to the total mass of the substance

  • If the substance is molecular you can use the term relative molecular mass, but this term should not be used for ionic compounds such as sodium chloride

  • To calculate the Mr of a substance, you have to add up the relative atomic masses of all the atoms present in the formula

Relative Formula Mass Calculations Table

Relative Formula Mass Calculations Table, downloadable IGCSE & GCSE Chemistry revision notes

  • In accordance with the Law of Conservation of Mass, the sum of the relative formula masses of the reactants will be the same as the sum of the relative formula masses of the products

Examiner Tips and Tricks

If you are in any doubt about whether to use the term relative molecular mass or relative formula mass, use the latter because it applies to all compounds whether they are ionic or covalent.

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Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Content Creator

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

Caroline Carroll

Reviewer: Caroline Carroll

Expertise: Head of Content Delivery

Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about delivering high-quality resources to help students achieve their full potential.