Using Mass Spectra - CGP

• What is the purpose of a mass spectrum?

  To analyze the composition of a sample
• How do you calculate the relative atomic mass (Aᵣ) from a mass spectrum?

  By using isotopic abundance and mass values
• What are the steps to calculate relative atomic mass from a mass spectrum?

  1. Read % relative isotopic abundance and mass.
  2. Multiply them for each isotope.
  3. Sum the totals.
  4. Divide by 100.
• What should you do if relative abundance is not given as a percentage?

  Divide by the total relative abundance
• How is a molecular ion formed in mass spectrometry?

  • Formed by removing one electron from a molecule
  • Results in a peak with mass/charge ratio equal to M
• How do you identify an unknown compound using mass spectrometry?

  By comparing mass/charge ratio to known values