IBChemistry: SLDPTopic Questions11. Measurements & Data Processes11.1 Spectroscopic Identification

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First teaching 2014

Last exams 2024

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Spectroscopic Identification (DP IB Chemistry: SL)

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11.1 Spectroscopic Identification

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11.1 Spectroscopic Identification

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11 mark

Which of the following statements about propanal, CH3CH2CHO, and propanone, CH3COCH3 is not correct? 

The compounds have:

  • molecular ion peaks at different mass to charge ratios

  • different fragmentation patterns in the mass spectrum

  • absorption in the infrared spectrum due to the carbonyl group

  • a different fingerprint region in the infrared spectrum

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21 mark

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

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

 

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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    31 mark

    Which of the following cannot be obtained from an infrared spectrum?

    • the molecular mass

    • the presence of C=O bonds

    • the presence of O-H bonds

    • the identity of a compound through comparison with other spectra

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    41 mark

    What is the index of hydrogen deficiency (IHD) for the molecule shown below?

    11-1-mcq-q4-easy-ib-chemistry

    • 1

    • 2

    • 4

    • 5

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    51 mark

    What information can be determined from the infrared spectrum of a molecule?

    • The number of hydrogens

    • The number of hydrogen environments

    • The type of bonds present

    • The relative molecular mass

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    61 mark

    Which of the following bonds will produce strong absorptions in the infrared part of the electromagnetic spectrum? 

      1.    C-N
      2.    O=O
      3.    C=O

    • I and II only  

    • I and III only  

    • II and III only 

    • I, II and III

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    71 mark

    Which of the following is true about the fingerprint region in the IR spectrum of alcohols?

    • The fingerprint region is where single bonds can be identified in the IR spectrum  

    • The fingerprint region is unique to every molecule  

    • The fingerprint region does not provide useful information about molecules 

    • A functional group can be identified from the fingerprint region

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    81 mark

    Which of the following statements is correct about spectroscopic techniques for organic molecules?

    • Information about bond vibrations can be deduced from mass spectroscopy 

    • The values of carbon–hydrogen bond lengths can be found from 1H NMR spectroscopy 

    • The number of hydrogen atoms can be determined from infrared spectroscopy

    • Information about molecular structure can be found from mass spectroscopy

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    91 mark

    In the 1H NMR spectrum of 3-methylbutan-1-ol what is the ratio of the peak areas under each signal?

    • 6 : 1 : 2 : 2 : 1

    • 3 : 3 : 1 : 5 : 1

    • 6 : 1 : 5 : 1

    • 3 : 3 : 1 : 2 : 3

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    101 mark

    Which of the following types of spectroscopic identification will involve bond fission in organic molecules?

    • Nuclear magnetic spectroscopy  

    • Infrared spectroscopy 

    • Mass spectrometry 

    • X-ray crystallography

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    11 mark

    Which alcohol is not likely to have a fragment 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 shown below is likely to have a fragment at m/e = 45 in its mass spectrum?

    11-1-mcq-q2-medium-ib-chemistry

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      31 mark

      Chlorine has two isotopes 35Cl and 37Cl.  Assuming in the molecule C4H6Cl4 there is only one hydrogen and one carbon isotope, how many molecular ion peaks will be seen in its mass spectrum?

      • 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

      The infrared spectrum of a compound is shown below.

      d6mgC1_0_11-1-mcq-q7-medium-ib-chemistry

      Use the infrared absorptions, in wavenumbers, to identify the compound 

      bond

      wavenumber range/ cm-1

      O−H (alcohol)

      3750 – 3200

      C−H (alkane)

      2962 – 2853

      C−H (aldehyde)

      2900 – 2820 and 2775 – 2700

      C═O (aldehyde or ketone)

      1740 - 1680

       

      Which compound is shown by the infrared spectrum?

      • propan-1-ol

      • propan-2-ol

      • propanal

      • propanone

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      81 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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      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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      101 mark

      Below is a 1H NMR spectrum for an unknown organic compound. The relative areas under the peaks are labelled

      11-1-mcq-q10-medium-ib-chemistry

      Which of the following compounds could give this spectrum?

      • propan-1-ol, CH3CH2CH2OH

      • propan-2-ol, CH3CH(OH)CH3

      • methyoxyethane, CH3OCH2CH3

      • pentan-2-one, CH3CH2CH2COCH3

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      11 mark

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

      11-1-mcq-q1-fig-1-hard-ib-chemistry

      11-1-mcq-q1-fig-2-hard-ib-chemistry

      11-1-mcq-q1-fig-3-hard-ib-chemistry

      What evidence from the spectra of the three compounds A, B and C, suggests they could be isomers?

      • 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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      21 mark

      The infrared spectrum below shows an unknown compound.

      11-1-mcq-q2-hard-ib-chemistry

      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

      Which compound could have produced the infrared spectrum?

      11-1-mcq-q2-ma-hard-ib-chemistry

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        31 mark

        The diagram shows an infrared spectrum of a compound.

        11-1-mcq-q3-hard-ib-chemistry

        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

        Which compound would give this spectrum?

        • butanoic acid

        • butanal

        • butan-1-ol

        • 1-bromobutane

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        41 mark

        Which of the following infrared spectra could show a carboxylic acid?

        11-1-mcq-q4-fig-1-hard-ib-chemistry

        11-1-mcq-q4-fig-2-hard-ib-chemistry

        11-1-mcq-q4-fig-3-hard-ib-chemistry

        11-1-mcq-q4-fig-4-hard-ib-chemistry

        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

          Choose your answer

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          51 mark

          A periodic table is needed for this question 

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

          Which of the following statements is incorrect?

          • n = 5

          • the compound could contain bromine

          • there are no isotopes of X or F

          • the compound is a fluoride of iodine

          Choose your answer

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          61 mark

          An organic compound is analysed by mass spectrometry and infrared spectroscopy. The following 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

           

          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

           

          Which of the following compounds could be consistent with the data given?

          11-1-mcq-q6-hard-ib-chemistry

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            71 mark

            What does the 1H NMR spectrum below tell you about a molecule?

            11-1-mcq-q7-hard-ib-chemistry

            • There is only one isotope of hydrogen present in the molecule

            • The molecule is a hydrocarbon

            • There is only one hydrogen atom in the molecule

            • There is only one hydrogen environment in the molecule

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            81 mark

            How many peaks would you expect to see in a 1H NMR spectrum of methylbenzene?

            11-1-mcq-q8-hard-ib-chemistry

            • 3

            • 4

            • 5

            • 6

            Choose your answer

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            91 mark

            What is the index of hydrogen deficiency (IHD) for this molecule of aspirin?

            11-1-mcq-q9-hard-ib-chemistry

            • 3

            • 4

            • 5

            • 6

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            101 mark

            Which molecule has an index of hydrogen deficiency (IHD) = 1?

            • C6H10

            • C2Br2

            • C4H9N

            • C3H8O

            Choose your answer

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