Lesson 19A.1

19A.1 Interpreting mass spectra Quiz: Pearson Edexcel Chemistry, Unit 19

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 19A.1, Interpreting mass spectra: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 19: Modern Analytical Techniques II, written with Revision Ninja.

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The 20 questions

  1. What information is provided by the molecular ion peak in a mass spectrum?

    • Empirical formula mass
    • Base fragment mass
    • Relative molecular mass
    • Most abundant mass

  2. What feature defines the base peak in a mass spectrum?

    • Highest mass-to-charge ratio
    • Highest relative abundance
    • Lowest relative abundance
    • Unfragmented molecular ion

  3. What occurs during electron impact ionisation in a mass spectrometer?

    • Laser desorption emission
    • Thermal proton transfer
    • Electrospray droplet evaporation
    • High-energy electron bombardment

  4. What is the correct sequence of stages in a mass spectrometer?

    • Deflection, ionisation, acceleration, detection
    • Ionisation, deflection, acceleration, detection
    • Acceleration, ionisation, deflection, detection
    • Ionisation, acceleration, deflection, detection

  5. A compound shows peaks at M and M+2 in a 3:1 ratio. Which element is most likely present?

    • Iodine
    • Bromine
    • Fluorine
    • Chlorine

  6. A compound shows peaks at M and M+2 of nearly equal height. Which element is most likely present?

    • Bromine
    • Chlorine
    • Fluorine
    • Carbon

  7. Which fragment ion causes a peak at m/z 15 in a mass spectrum?

    • OH+
    • C2H5 constellation
    • CHO+
    • CH3+

  8. Which fragment ion causes the prominent m/z 43 peak in methyl ketones?

    • CH3CH2 ion
    • C3H7 ion
    • COOH ion
    • CH3CO sequence

  9. What is the approximate relative height of the M+1 peak per carbon atom?

    • 1.1%
    • 0.1%
    • 11.0%
    • 5.5%

  10. A compound's M+1 peak is about 3.3% of the M peak. How many carbon atoms are most likely present?

    • 6
    • 1
    • 3
    • 2

  11. Calculate the accurate relative molecular mass of CO2 using C = 12.0000 and O = 15.9949.

    • 43.9800
    • 44.0100
    • 43.9949
    • 43.9898

  12. A compound has an accurate molecular ion at 44.0624. Which formula fits?

    • C3H8
    • CH4N2
    • C2H4O
    • CO2

  13. A compound has an accurate molecular mass of 46.0417. Which molecular formula fits?

    • CH2O2
    • CH4N2
    • C2H6O
    • C3H10

  14. A compound has an accurate molecular mass of 58.0417. Which molecular formula is consistent with this?

    • C3H6O
    • C4H10
    • C2H2O2
    • C3H8N

  15. A compound has an accurate molecular mass of 60.0211. Which formula fits?

    • CH4N2O
    • C2H6N2
    • C3H8O
    • C2H4O2

  16. A compound has an accurate molecular mass of 88.0522. Which formula fits?

    • C3H8N2O
    • C4H8O2
    • C4H10N2
    • C5H12O

  17. What feature is indicated by an odd molecular ion mass in mass spectrometry?

    • Even oxygen count
    • Even nitrogen count
    • Odd chlorine count
    • Odd nitrogen count

  18. A mass spectrum of an unknown has a molecular ion at m/z 74 and a strong peak at m/z 31. Which compound fits?

    • Benzene, C6H6
    • Propanone, CH3COCH3
    • Ethanoic acid, CH3COOH
    • Butan-1-ol, C4H9OH

  19. A fragment peak drops from m/z 60 to m/z 45. What species was lost?

    • OH group
    • COOH group
    • CH3 group
    • C2H5 group

  20. Equal-height M and M+2 peaks in a mass spectrum indicate which element?

    • Two chlorine atoms
    • One chlorine atom
    • One iodine atom
    • One bromine atom

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