7B.1 Identifying functional groups from IR spectra Quiz: Pearson Edexcel Chemistry, Unit 7

The 20 questions

1. Which wavenumber range in an IR spectrum indicates the O-H group in an alcohol?

   • 1620–1680 cm⁻¹
   • 3200–3550 cm⁻¹
   • 1700–1750 cm⁻¹
   • 2500–3300 cm⁻¹

2. Which IR absorption wavenumber range is characteristic of a ketone C=O bond?

   • 1700–1750 cm⁻¹
   • 3200–3550 cm⁻¹
   • 1620–1680 cm⁻¹
   • 2200–2260 cm⁻¹

3. Which broad IR absorption peak distinguishes a carboxylic acid from an aldehyde?

   • 1620–1680 cm⁻¹
   • 3200–3550 cm⁻¹
   • 1700–1750 cm⁻¹
   • 2500–3300 cm⁻¹

4. Which IR absorption wavenumber range is characteristic of a C=C bond in an alkene?

   • 3200–3550 cm⁻¹
   • 2200–2260 cm⁻¹
   • 1700–1750 cm⁻¹
   • 1620–1680 cm⁻¹

5. Which IR absorption wavenumber range indicates the N-H group in an amine?

   • 1700–1750 cm⁻¹
   • 1620–1680 cm⁻¹
   • 2500–3300 cm⁻¹
   • 3300–3500 cm⁻¹

6. Which wavenumber range is characteristic of C-H stretching in alkanes?

   • About 2850 to 3000 cm-1
   • About 1700 to 1750 cm-1
   • About 3200 to 3550 cm-1
   • About 1620 to 1680 cm-1

7. Which pair of weak IR absorption peaks helps distinguish an aldehyde from a ketone?

   • 1620 and 1680 cm⁻¹
   • 2700 and 2800 cm⁻¹
   • 3200 and 3550 cm⁻¹
   • 1700 and 1750 cm⁻¹

8. A compound shows a strong sharp absorption at 1715 cm-1 and a very broad band from 2500 to 3300 cm-1. What is it most likely to be?

   • An alcohol
   • An alkene
   • A carboxylic acid
   • A primary amine

9. Which IR wavenumber range is characteristic of the C=O stretch in an ester?

   • 1735–1750 cm⁻¹
   • 2500–3300 cm⁻¹
   • 3200–3550 cm⁻¹
   • 1620–1680 cm⁻¹

10. Which compound would show a broad absorption at 3200 to 3550 cm-1 and a C-O absorption near 1050 cm-1?

    • Ethanal
    • Ethene
    • Ethanol
    • Ethane

11. What causes molecules to absorb specific frequencies in infrared spectroscopy?

    • Bond vibrations
    • Molecular rotations
    • Electron transitions
    • Nuclear spin flips

12. Which region of an IR spectrum is used to identify specific functional groups?

    • Below 1000 cm⁻¹
    • Above 1500 cm⁻¹
    • Above 4000 cm⁻¹
    • Below 1500 cm⁻¹

13. Which wavenumber range corresponds to an alkene or aromatic C-H stretch in an IR spectrum?

    • 1620 to 1680 cm-1
    • 3200 to 3600 cm-1
    • 2850 to 2990 cm-1
    • 3000 to 3100 cm-1

14. Which compound shows a C=O stretch around 1715 cm-1 but no broad O-H band?

    • Propanoic acid
    • Propene
    • Propanone
    • Propan-1-ol

15. A compound has IR absorptions at 3350 cm-1 (broad) and 1050 cm-1 but no peak at 1700 cm-1. Which compound best fits?

    • Propene
    • Propan-2-ol
    • Propanone
    • Propanal

16. Which bond vibration produces an IR absorption peak near 1650 cm-1 in an alkene?

    • C=C stretch
    • C-H stretch
    • O-H stretch
    • C-O stretch

17. How do N-H stretching absorption bands of amines differ from O-H bands of alcohols?

    • Sharper bands
    • Lower wavenumber
    • Higher intensity
    • Broader bands

18. Which IR absorption feature is characteristic of a carboxylic acid O-H group?

    • 3200 to 3600 cm-1
    • 1620 to 1680 cm-1
    • 2500 to 3300 cm-1
    • 3300 to 3500 cm-1

19. A student records an IR spectrum with no absorption between 3200 and 3550 cm-1 and no absorption at 1700 cm-1. Which compound is most likely?

    • Hexane
    • Butan-1-amine
    • Ethanoic acid
    • Ethanol

20. Which region of the IR spectrum contains the C-O single bond stretch used to support an alcohol identification?

    • Around 3300 to 3500 cm-1
    • Around 1000 to 1300 cm-1
    • Around 2850 to 3000 cm-1
    • Around 1620 to 1680 cm-1

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