Lesson 7A.1

7A.1 Using mass spectrometer data Quiz: Pearson Edexcel Chemistry, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 7A.1, Using mass spectrometer data: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 7: Modern Analytical Techniques I, written with Revision Ninja.

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The 20 questions

  1. In mass spectrometry, which peak is used to determine the relative molecular mass of an organic compound?

    • The molecular ion peak, M+
    • The base peak, which is always the tallest
    • The peak at m/z = 1 from the hydrogen ion
    • The peak at the lowest m/z value of all fragments

  2. A compound shows a molecular ion peak at m/z = 58. What is its likely relative molecular mass?

    • 57
    • 58
    • 29
    • 116

  3. The mass spectrum of an organic compound has a peak at m/z 43 and another at m/z 58. Which species is most likely formed by fragmentation at m/z 43?

    • C2H5+, from loss of hydrogen chloride, which is a common fragmentation of a chloroalkane
    • CH3CO+, from loss of a methyl group from propanone
    • C3H8+, from loss of an oxygen atom, which would leave a fragment with no carbonyl group present
    • CH2OH+, from loss of a methyl radical, which is the typical fragment of a primary alcohol

  4. An organic compound has a molecular ion peak at m/z 46. A major fragment appears at m/z 31. Which fragment is most consistent with an alcohol?

    • C2H5+
    • CH2OH+
    • CH3+
    • CHO+

  5. A mass spectrum shows molecular ion peaks at m/z 79 and 81 of roughly equal height. Which element is most likely present?

    • Chlorine, from the 35Cl and 37Cl isotopes
    • Carbon, from the 12C and 13C isotopes
    • Oxygen, from the 16O and 18O isotopes
    • Bromine, from the 79Br and 81Br isotopes

  6. What relative molecular mass is indicated by a molecular ion peak at m/z 72 for a compound that is a pentane isomer?

    • 58
    • 86
    • 72
    • 144

  7. Which fragment is most likely to have m/z 15 in the mass spectrum of an alkane?

    • C3H7+
    • C4H9+
    • CH3+
    • C2H5+

  8. Which fragment appears at m/z 29 for an alkane such as butane?

    • C4H9+
    • C2H5+
    • C3H7+
    • CH3+

  9. What is the relative molecular mass of a compound whose molecular ion peak is at m/z 88, and which fragments by losing 15 units?

    • 88, with a fragment at m/z 73 from loss of CH3
    • 88, with a fragment at m/z 58 from loss of CH3
    • 73, because the molecular ion is the fragment
    • 15, because the fragment has the lowest mass

  10. In mass spectrometry, what does the term base peak mean?

    • The peak produced by the carrier gas
    • The molecular ion that has the highest mass
    • The peak formed by the solvent used in the sample
    • The most abundant ion, shown at 100% relative abundance

  11. A compound contains one chlorine atom and has a molecular ion at m/z 64 and an M+2 peak at m/z 66. What is the approximate ratio of their heights?

    • 2:1
    • 1:1
    • 3:1
    • 1:3

  12. Which ion is responsible for the peak at m/z 31 in the mass spectrum of methanol?

    • CH3+
    • CHO+
    • CH2OH+
    • OCH3-

  13. What is the relative molecular mass of an alkene whose molecular ion peak appears at m/z 56?

    • 42, as C3H6
    • 112, as C8H16
    • 28, as C2H4
    • 56, as C4H8

  14. Which ion would be expected from the fragmentation of 2-chloropropane (Mr 78.5) at m/z 43?

    • CH3CHCl+, from loss of oxygen
    • C3H7+, from loss of the chlorine atom
    • CH2Cl+, from loss of a methyl radical
    • C2H5Cl+, from loss of hydrogen

  15. Why does the molecular ion peak sometimes have a very small height in a mass spectrum?

    • Some molecules fragment readily, so few intact molecular ions survive to be detected
    • The molecular ion has no mass and so is not recorded by the instrument in any spectrum
    • The molecular ion is always absorbed by the detector before it can reach the ion collector plate
    • The sample contains no carbon atoms and so the molecular ion cannot form in the chamber

  16. What is the mass difference between the M+ peak and an M-15 fragment peak?

    • 28 mass units, equivalent to a loss of C2H4
    • 17 mass units, equivalent to a loss of OH
    • 15 mass units, equivalent to a loss of CH3
    • 1 mass unit, equivalent to a loss of H

  17. Which fragment at m/z 57 is consistent with the mass spectrum of butane, C4H10 (Mr 58)?

    • C2H5+, formed by loss of an ethyl group
    • C4H9+, formed by loss of a hydrogen atom
    • C3H7+, formed by loss of a methyl group
    • CH3+, formed by loss of a propyl group

  18. What is the expected m/z value of the molecular ion of chloroethane, C2H5Cl, for the 35Cl isotope?

    • 64
    • 66
    • 65
    • 29

  19. What relative molecular mass is shown by the molecular ion peak of ethanoic acid, CH3COOH?

    • 60
    • 44
    • 45
    • 74

  20. A compound shows a molecular ion at m/z 72 and a fragment at m/z 57. What is the mass lost in forming the fragment?

    • 17, consistent with loss of an OH group
    • 1, consistent with loss of a hydrogen atom
    • 28, consistent with loss of an ethene unit
    • 15, consistent with loss of a methyl group

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