Relative Formula Mass (Edexcel GCSE Chemistry)
Revision Note
Did this video help you?
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
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.
You've read 0 of your 5 free revision notes this week
Sign up now. It’s free!
Did this page help you?