CIE AS Chemistry (9701) exams from 2022

Revision Notes

4.1.3 Isotopic Abundance & Relative Atomic Mass

Calculating Relative Atomic Mass

  • Isotopes are different atoms of the same element that contain the same number of protons and electrons but a different number of neutrons.
    • These are atoms of the same elements but with different mass numbers
  • Because of this, the mass of an element is given as relative atomic mass (Ar) by using the average mass of the isotopes
  • The relative atomic mass of an element can be calculated by using the relative abundance values
    • The relative abundance of an isotope is either given or can be read off the mass spectrum

Calculating Relative Atomic Mass equation 1

Worked example: Calculating relative atomic mass of oxygen

Analytical Techniques Worked example - Calculating relative atomic mass of oxygen, downloadable AS & A Level Chemistry revision notes

Answer 

The correct answer is 1

Calculating Relative Atomic Mass worked example equation 1

= 16.0044

= 16.00

Worked example: Calculating relative atomic mass of boron

Analytical Techniques Worked example - Calculating relative atomic mass of boron, downloadable AS & A Level Chemistry revision notes

Analytical Techniques Mass Spectrum Boron, downloadable AS & A Level Chemistry revision notes

Answer

 Calculating Relative Atomic Mass worked example equation 2

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
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