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

In partnership with Revision Ninja

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.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What does the molecular ion peak in a mass spectrum give?

    • A fragment formed by loss of a hydrogen atom from the molecule, which appears one unit below the molecular mass
    • An ion formed by gaining an electron, with a mass one unit above the molecular mass in the spectrum
    • The most abundant fragment ion, with the highest intensity, which is always the one that shows the molecular mass
    • The relative molecular mass of the compound, from the ion formed by loss of one electron

  2. What is the base peak in a mass spectrum?

    • The most intense peak, assigned 100% relative abundance
    • The peak with the largest m/z value in the spectrum
    • The molecular ion peak, which is always the tallest
    • The peak arising from carbon-13 isotopes only

  3. What is the first stage of electron impact ionisation in mass spectrometry?

    • Bombardment of the vapour with high-energy electrons to form positive ions
    • Passing the sample through a column of silica gel in a stream of inert carrier gas
    • Dissolving the sample in a deuterated solvent so that the ions form in the solution
    • Heating the solid until it melts into a liquid, which then flows into the ionisation chamber

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

    • Ionisation, acceleration, deflection by mass-to-charge ratio, then detection
    • Acceleration, detection, ionisation, then deflection, with the ions being formed after the detector
    • Detection, ionisation, acceleration, then deflection, with the ions being recorded at the start
    • Ionisation, detection, deflection, then acceleration, so the ions are detected before they are separated

  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. A peak at m/z 15 in a mass spectrum most likely arises from which ion?

    • CO+, a carbon monoxide ion
    • C2H5+, an ethyl ion
    • CH3+, a methyl ion
    • OH+, a hydroxyl ion

  8. An unknown compound shows a peak at m/z 43 that is strong in methyl ketones. What ion is most likely?

    • CH2OH+, a hydroxymethyl ion
    • CH3CH2+, an ethyl ion
    • CH3CO+, an acylium ion
    • COOH+, a carboxyl ion

  9. Which statement about the isotope peak M+1 is correct?

    • It is always taller than the M peak in any organic compound with more than two carbon atoms present
    • It is caused only by oxygen atoms in the molecule, since oxygen has a heavy isotope present
    • Its relative height is about 1.1% of the M peak for each carbon atom present
    • It is present only when the compound contains a halogen atom, which gives the isotope pattern

  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. A compound has an odd nominal molecular mass, such as 31 for methylamine. What does this suggest?

    • The compound contains an odd number of nitrogen atoms
    • The compound contains no nitrogen and no halogen
    • The compound contains only aromatic carbon
    • The compound contains an even number of nitrogen atoms

  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 compound's molecular ion is at m/z 60 and a fragment at m/z 45 appears. What has been lost?

    • A hydroxyl group, OH, with mass 17
    • A methyl group, CH3, with mass 15
    • A hydrogen atom, with mass 1
    • A carbonyl group, CO, with mass 28

  20. M and M+2 peaks of nearly equal height at 2 mass units apart would indicate which element in a fragment?

    • One carbon atom in a large molecule
    • One chlorine atom
    • One bromine atom
    • One sulfur atom in an aromatic ring

All Pearson Edexcel Chemistry quizzes