Topic Three (1.3): Mass Spectrometry
Introduction
Mass Spectrometry is a very important technique used by chemists in research laboratories. You should be able to understand the basic principles of this technique and interpret spectra obtained to deduce the chemical composition of a given sample.
Reading
Edexcel AS/A Level Chemistry Student Book 1 pages 12 to 15, pages 32 to 33
Tasks
Complete the following:
- Read pages 12 to 15, making appropriate notes (include key definitions).
- Complete the ‘in-text’ questions.
WATCH - Mass Spectrometry MS - RSC (YouTube) Links to an external site.
WATCH - Physical Chemistry - Interpretation of Mass Spectra (MASSOLIT) Links to an external site.
- Complete questions 1 and 6 on pages 32 to 33.
Top Tips
Make sure that you understand the following key points:
- The Z number is not the same as the relative isotopic mass. This is the number which appears on the periodic table which takes account of the relative proportion of each isotope of an element so Z might not be a whole number.
- You should use the Z number in calculations.
- When considering spectra of molecules always look for the molecular ion peak (M) which will be furthest to the right. In larger molecules there might be a tiny peak due to the presence of 13C, the M+1 peak. Ignore this.
Key Terms
Add the following subject vocabulary with definitions to your glossary.
- Relative atomic mass Ar
- Relative isotopic mass
- Molecular ion peak