ASChemistryCIEExam Questions22. Analytical Techniques22.2 Mass Spectrometry

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First teaching 2023

First exams 2025

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Mass Spectrometry (CIE AS Chemistry)

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22.2 Mass Spectrometry

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22.2 Mass Spectrometry

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11 mark

Which of the following corresponds to the base peak in a mass spectrum?

  • The peak corresponding to the ion with lowest m/e.

  • The peak corresponding to the molecular ion.

  • The peak corresponding to any ion formed by the fragmentation of the molecule.

  • The peak corresponding to the most abundant ion.

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21 mark

The diagram shows the structure of ricinoleic acid.

4-1-e-2

Which fragment would produce the tallest peak in the mass spectrum of ricinoleic acid at m/e = 55?

  • CH2CO2+

  • CH═CHCHOH+

  • C4H7+

  • COOH+

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31 mark

In a mass spectrometer, the ions are separated.

Which of the following species will be deflected to the greatest extent?

  • 37Na+

  • 35Na+

  • 37Na

  • 35Na2+

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41 mark

A sample of silicon contains the following isotopes

Isotope

Percentage abundance

28Si

81.21

29Si

14.10

30Si

4.69

What is the relative atomic mass of silicon in this sample, to 1dp?

  • 29.8

  • 29.0

  • 28.2

  • 28.0

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51 mark

Chlorine exists as two isotopes with mass numbers 35 and 37. A sample of chlorine contains 75.3% of chlorine-35 atoms.

What is the relative atomic mass of chlorine in this sample, to 2dp?

  • 35.16

  • 36.00

  • 35.49

  • 35.00

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61 mark

A sample of neon contains the following isotopes

Isotope

Percentage abundance

20Ne

90.92

21Ne

0.26

22Ne

8.82

What is the relative atomic mass of neon in this sample, to 2dp?

  • 21.00

  • 20.18

  • 20.09

  • 20.00

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71 mark

Nitrogen trichloride has the formula NCl3, a sample was found to contain only nitrogen atoms with mass number 14, and chlorine atoms with mass numbers 35 and 37.

Which of the following ions and mass/charge ratio for the ions responsible for the molecular ion peaks in the mass spectrum of nitrogen trichloride is incorrect?

 

Ion

m/e

A

N(35Cl)3+

119

B

N(35Cl)237Cl+

121

C

N35Cl(37Cl)2+

123

D

N(37Cl)2+

125

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    81 mark

    The mass spectrum of silicon is shown below.

    4-1-e-9

    What is the best estimate for the relative atomic mass of silicon in this sample?

    • 29.0

    • 28.8

    • 28.3

    • 28.0

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    11 mark

    Which alcohol is not likely to have a fragment ion at m/e at 43 in its mass spectrum?

    • (CH3)2CHCH2OH

    • CH3CH(OH)CH2CH2CH3

    • CH3CH2CH2CH2OH

    • CH3CH2CH(OH)CH3

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    21 mark

    Which of the compounds below is not likely to have a fragment ion at m/e = 43 in its mass spectrum?

    • 4-1-m-2a

    • 4-1-m-2b

    • 4-1-m-2c

    • 4-1-m-2d

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    31 mark

    Assuming that chlorine has only two isotopes and hydrogen and carbon as one, how many molecular ion peaks will be shown in the mass spectrum of C4H6Cl4?

    • 5

    • 4

    • 3

    • 2

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    41 mark

    Bromine exists as two isotopes 79Br and 81Br, which are found in almost equal abundance.

    Which of the following statements is correct?

    • 79Br is more reactive than 81Br.

    • The mass spectrum of C3H7Br has two molecular ion peaks at 122 and 124.

    • The atomic radius of 79Br is less than the atomic radius of 81Br.

    • The first ionisation energy of 79Br is less than the first ionisation energy of 81Br.

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    51 mark

    Which alcohol is likely to have a fragment ion at m/e = 31 in its mass spectrum?

    • (CH3)2CHCH2OH

    • CH3CH(OH)CH2CH2CH3

    • CH3CH2CH2C(OH)(CH3)2

    • CH3CH2CH(OH)CH3

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    61 mark

    Which pair of compounds would you expect to both have a singly charged peak at m/e = 29 in the mass spectrum?

    • Propan-1-ol and propanal

    • Propanal and propanone

    • Propan-2-ol and propanal

    • Propan-1-ol and propan-2-ol

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    71 mark

    Which of the ketones listed would not be expected to have a peak in its mass spectrum at m/e = 57?

    • Hexan-3-one, CH3CH2CH2COCH2CH3

    • Pentan-3-one, CH3CH2COCH2CH3

    • 3-methylbutanone, (CH3)2CHCOCH3

    • Butanone, CH3CH2COCH3

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    81 mark

    Chlorine has two isotopes, 35Cl and 37Cl. 

    What is the number of molecular ion peaks in the mass spectrum of a sample of Cl2?

    • 5

    • 4

    • 3

    • 2

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    91 mark

    Which of the following statements about the mass spectrum of CH3Br is correct?

    • There is one peak for the molecular ion with an m/e value of 44.

    • There is one peak for the molecular ion with an m/e value of 95.

    • The last two peaks have abundances in the ratio 3:1 and occur at m/e values of 94 and 96.

    • The last two peaks are of equal size and occur at m/e values of 94 and 96.

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    11 mark

    Two stable isotopes of bromine have relative masses of 79 and 81. 

    Which is the correct pattern of peaks in the mass spectrum of molecular bromine?

    • b0gDg7dh_4-1-h-2a

    • 4-1-h-2b

    • 4-1-h-2c

    • 4-1-h-2d

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    21 mark

    The mass spectra of three compounds A, B and C are shown below.

    4-1-h-3a

    4-1-h-3b

    4-1-h-3c

    Which of the following features of the three compounds A, B and C shows the molecular formula is C4H10O?

    • All show a molecular ion peak at 74

    • All show a molecular ion peak at 13

    • All show a molecular ion peak at 73

    • All show a molecular ion peak at 33

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    31 mark

    Chlorine exists as two isotopes 35Cl and 37Cl in the ratio 3:1.

    Which of the following statements about the molecular ion peaks in the mass spectrum of Cl2 is correct?

    • Peaks at m/e = 70 and 72 in the ratio 3:1

    • Peaks at m/e = 70, 72 and 74 in the ratio 9:3:1

    • Peaks at m/e = 70, 72 and 74 in the ratio 9:6:1

    • Peaks at m/e = 70 and 74 in the ratio 3:1

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    41 mark

    A compound XFn is a fluoride of another halogen, X, and it is known that n > 1. The highest mass peak in the spectrum of XFn is assigned to the parent ion and comes as single peak at m/e = 222. 

    Which of the following statements is incorrect?

    • n = 5

    • The compound could contain bromine

    • X and F are monotopic

    • The compound is a fluoride of iodine

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    51 mark

    In the mass spectrum of trifluoroacetic acid, CF3CO2H, intense peaks are observed at m/e = 69 and 45 (base peak) in addition to other peaks. 

    The peak at m/e = 69 is accompanied by a peak at m/e = 70, which is about 1.1% the intensity of the peak at m/e = 69. 

    Which of the following statements is not supported by this information?

    • C−C bond cleavage occurs

    • Fluorine is monotopic

    • [HO2C]+ is a fragment ion

    • CF3CO2H fragments by sequential loss of F atoms

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    61 mark

    A sample is analysed by mass spectrometry and infrared spectroscopy. The following incomplete data is obtained.

    Mass spectrometry

    Infrared spectroscopy

    Molecular ion peak at m/e = 128

    Sharp peak at 1720 cm-1

    Fragment ion peak at m/e = 15

    No broad peak around 3200 cm-1

    Which of the following compounds is demonstrated by this data?

    Bond

    Wavenumber range / cm-1

    C−O; hydroxyl, ester

    1040 – 1300

    C═C; aromatic compound, alkene

    1500 - 1680

    C═O amide

    carbonyl, carboxyl

    ester

    1640 – 1690

    1670 – 1740 

    1710 - 1750

    C≡N; nitrile

    2200 – 2250

    C−H; alkane

    2850 – 2950

    N−H; amine, amide

    3300 – 3500

    O−H; carboxyl

    hydroxyl

    2500 – 3000

    3200 - 3600

    • 4-1-h-10a

    • 4-1-h-10b

    • 4-1-h-10c

    • 4-1-h-10d

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