- 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 molecule
- 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 molecular masses of the reactants will be the same as the sum of the relative molecular masses of the products
The relative atomic mass of every element is given on the Periodic Table. It is the larger of the two numbers.
- The percentage by mass of an element in a compound can be calculated using the following equation:
Calculate the percentage by mass of calcium in calcium carbonate, CaCO3
Don’t forget to multiply your answer by 100 in order to convert it to a percentage.