Lesson 3.3.6.2

3.3.6.2 Mass spectrometry Quiz: AQA Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.3.6.2, Mass spectrometry: 20 multiple choice questions for the AQA Chemistry (7405), Unit 3: Organic chemistry, written with Revision Ninja.

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The 20 questions

  1. In mass spectrometry, what does the molecular ion peak (M+) usually indicate?

    • The number of carbon atoms in the molecule
    • The relative molecular mass of the compound
    • The boiling point of the sample
    • The mass of the most abundant fragment only

  2. Which process forms the molecular ion in electron ionisation mass spectrometry?

    • Addition of a proton to the molecule
    • Removal of one electron from the molecule
    • Loss of a neutron from the nucleus
    • Splitting of the molecule into two equal halves

  3. Why are precise atomic masses used, rather than whole-number masses, to find a molecular formula?

    • Precise masses make the spectrum peaks taller and easier to read on the detector
    • Different formulae can share the same nominal mass but have different precise masses
    • Precise masses show how many isotopes each element has in the sample being tested
    • Whole-number masses cannot be added together to give a total for a molecule

  4. Which molecular formula has a precise molecular mass of 44.0261?

    • N2O
    • CO2
    • C3H8
    • C2H4O

  5. A compound has a precise molecular ion mass of 58.0417. Which molecular formula fits?

    • C3H6O
    • C2H6N2
    • C4H10
    • C2H2O2

  6. A compound has a precise molecular ion mass of 60.0573. Which molecular formula fits?

    • C4H12
    • C2H4O2
    • C3H8O
    • CH4N2O

  7. Compound X has a precise molecular ion mass of 88.0522. Which molecular formula is correct?

    • C4H8O2
    • C3H8N2O
    • C3H4O3
    • C5H12O

  8. A compound has a precise molecular ion mass of 46.0417. Which molecular formula fits?

    • CH4NO
    • C2H6O
    • CH2O2
    • C3H10

  9. A compound has a precise molecular ion mass of 74.0729. Which molecular formula fits?

    • C3H10N2
    • C4H10O
    • C2H6N2O
    • C3H6O2

  10. A compound has a precise molecular ion mass of 102.0678. Which molecular formula fits?

    • C5H10O2
    • C4H10N2O
    • C6H14O
    • C4H6O3

  11. Why can two different molecules have the same nominal mass in mass spectrometry?

    • Electron ionisation destroys all molecules of the same mass
    • Several molecular formulae can add up to the same whole-number mass
    • Nominal mass only counts the carbon atoms in a molecule
    • Two molecules with the same nominal mass always have the same formula

  12. Why may the molecular ion peak be weak or absent for some compounds?

    • Molecular ions are only formed in the solid state
    • Molecular ions are always stable and form the tallest peak
    • The molecular ion always has zero mass
    • The molecular ion can fragment readily after ionisation

  13. A compound contains only carbon, hydrogen and nitrogen, and its precise molecular ion mass is 58.0530. Which formula fits?

    • C3H6O
    • C2H2O2
    • C4H10
    • C2H6N2

  14. What is the degree of unsaturation for C4H8O2?

    • 0
    • 2
    • 1
    • 3

  15. A spectrum shows a molecular ion peak at m/z 44. Which statement is most accurate?

    • The compound could be several formulae such as C2H4O, C3H8 or CO2, so precise masses are needed
    • The compound must contain nitrogen because the molecular ion mass is above 40 units
    • The compound must be CO2 because m/z 44 is always carbon dioxide in the spectrometer
    • The compound must be an alkane because the molecular ion peak is at an even mass

  16. Why is relative molecular mass alone not enough to determine a molecular formula?

    • Relative molecular mass cannot be measured in a mass spectrometer
    • Several different formulae can have the same relative molecular mass
    • Molecular formulae never have the same mass as the molecular ion
    • Relative molecular mass only applies to inorganic compounds

  17. A compound has precise molecular ion mass 74.0366. Which molecular formula fits?

    • C3H6O2
    • C3H10N2
    • C2H6N2O
    • C4H10O

  18. A compound has precise molecular ion mass 58.0417 and contains only C, H and O. Which conclusion is best supported?

    • The formula is C3H6O because it matches the measured mass exactly
    • The formula is C2H2O2 because it has two oxygen atoms
    • The formula cannot be determined without an IR spectrum
    • The formula is C4H10 because nominal mass 58 is ambiguous

  19. What is the degree of unsaturation for a molecule with formula C5H10O2?

    • 1
    • 0
    • 2
    • 3

  20. Which use of mass spectrometry is named in the specification?

    • Measuring the rate of a chemical reaction by timing the formation of a precipitate
    • Counting the number of unpaired electrons in a transition metal ion in solution
    • Measuring the pH of a solution of the compound using a calibrated electrode
    • Determining the molecular formula of a compound using precise atomic masses

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