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EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 復(fù)習(xí)筆記：1.5.2 Calculate Relative Mass

Category: IGCSE課程, 國際課程 Date: 2022年11月11日下午3:03

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 復(fù)習(xí)筆記：1.5.2 Calculate Relative Mass

Relative Formula Mass & Relative Molecular Mass

We have seen previously that the symbol for the relative atomic mass is?A_r
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?M_r?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?M_r?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

3.1.2-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

Exam Tip

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