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Lesson: Mass Spectra

Worksheet • 6 Questions

Q1:

Why might mass analysis of a nitrogen-containing molecule show a molecular ion peak with an odd π‘š / 𝑧 ratio?

  • AIt contains an odd number of nitrogen atoms
  • BIt contains an even number of nitrogen atoms
  • CThe mass analyzer needs to be recalibrated; nitrogen containing molecules always give an even π‘š / 𝑧 ratio
  • DIt has rearranged via the McLafferty rearrangement

Q2:

In a mass spectrum of an alcohol, why is the molecular ion usually small or non-existent?

  • ACleavage of the C C bond adjacent to the hydroxyl group
  • BCleavage of the hydroxyl group
  • CFormation of a dimeric species
  • DRearrangement of the molecule to form an ester

Q3:

What is the likely explanation if a mass spectrum contains peaks at 35 and 37 Da?

  • AThe sample contains chlorine.
  • BThe sample contains bromine.
  • CThe sample is R b B r .
  • DThe sample was analyzed in a gas mixture containing krypton.
  • EThe sample was analyzed in a gas mixture containing argon.

Q4:

Which of the following chemical groups often display strong molecular ion peaks in mass spectra, due to their structural stability?

  • AAromatics
  • BAldehydes
  • CAlcohols
  • DCarboxylic acids
  • EAlkanes

Q5:

What are the typical units for the π‘₯ -axis of a mass spectrum?

  • AMass to charge ( π‘š / 𝑧 ) ratios
  • BMass (g)
  • CParts per million (ppm)
  • DWavelength (nm)
  • EWavenumbers ( ) c m βˆ’ 1

Q6:

Which of the following best describes the mass spectrum of fluorine ( F ) 2 ?

  • AIt consists of two peaks, appearing at 19 Da and 38 Da.
  • BIt consists of three peaks, appearing at 20, 21 and 22 Da.
  • CIt is similar to the spectra of bromine and chlorine.
  • DIt consists of two peaks, separated by 2 Da.
  • EIt consists of only one peak, since it is monoisotopic.
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