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CAIE A Level Chemistry 9701

Analytical techniques questions

Exam-style questions on Analytical techniques, ordered from foundation to challenge. Pick one, write your answer the way you would in the exam, and it comes back marked against the mark scheme, point by point.

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Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.

  1. Compare5 marksStandardThe carbon-13 NMR spectrum of an unknown compound A, with molecular formula C4H10O, consists of four peaks. The carbon-13 NMR spectrum of an isomer of A, compound B, also with molecular formula C4H10O, consists of only…
  2. Compare5 marksStandardThe table shows data from the mass spectra of two organic compounds, A and B. The spectra were recorded using electron impact ionisation. For each compound, the molecular ion (M+) peak and the [M+1]+ and [M+2]+ peaks…
  3. Describe5 marksStandardA mixture of the alkanes hexane, heptane and octane is separated using gas chromatography. The stationary phase is a high boiling point non-polar liquid coated on a solid support, and the mobile phase is an unreactive…
  4. Explain4 marksStandardA sample of propanal, CH3CH2CHO, is dissolved in a deuterated solvent and its proton NMR spectrum is recorded. The spectrum shows three peaks, with relative peak areas in the ratio 3 : 2 : 1. TMS is added as a…
  5. Compare5 marksStandardA chemist uses ^1H NMR spectroscopy to analyse two organic compounds, ethanol (CH3CH2OH) and methoxymethane (CH3OCH3). Compare the ^1H NMR spectra of these two compounds. In your answer you should discuss the number of…
  6. Suggest4 marksStandardA sample of chloromethane, CH3Cl, is analysed by mass spectrometry. The mass spectrum shows a molecular ion peak at m/e = 50 and another peak at m/e = 52. The relative abundance of the peak at m/e = 52 is about one…
  7. Explain4 marksStandardThe mass spectrum of an organic compound, Z, was recorded. The molecular ion peak is observed at m/z 84. The relative abundances of selected peaks are shown in the table. m/z relative abundance / % 84 100 85 5.5 86 32…
  8. Compare5 marksStandardThe mass spectrum of a bromoalkane shows a molecular ion peak at m/e = 122 and a peak of similar height at m/e = 124. The spectrum also shows a fragmentation peak at m/e = 43. Compare the information given by the peaks…
  9. Compare5 marksStandardA student carries out thin-layer chromatography (TLC) using a silica gel plate and a non-polar solvent. Two compounds, X and Y, are spotted separately. After development, the solvent front has travelled 8.0 cm from the…
  10. Suggest4 marksStandardA colourless liquid has the molecular formula C4H8O. Its infrared spectrum shows a strong, sharp absorption at 1715 cm^-1 and no absorption in the range 2700–2850 cm^-1. Suggest, with a reason, which functional group…
  11. Describe5 marksStandardA student records the infrared spectrum of a colourless liquid with the molecular formula C3H8O. The spectrum shows a strong, broad absorption between 3230 and 3550 cm^-1 and a strong absorption at 1050 cm^-1. No…
  12. Explain4 marksStandardA student records the mass spectrum of a volatile organic compound, X, which contains only carbon, hydrogen and bromine. The molecular ion peak, M+, appears at m/e = 122, with a relative abundance of 50. A peak at m/e…
  13. Explain4 marksStandardAn unknown compound has the molecular formula C3H6O2. Its infrared spectrum shows a strong, broad absorption between 2500 and 3300 cm⁻¹, a strong absorption at 1710 cm⁻¹, and a strong absorption at 1250 cm⁻¹. Explain…
  14. Suggest4 marksStandardA student records the proton NMR spectrum of a colourless liquid with the molecular formula C4H8O2. The spectrum shows three signals. Signal A: chemical shift 1.1 ppm, integration ratio 3, triplet Signal B: chemical…
  15. Explain4 marksStandardThe infrared spectrum of a compound with molecular formula C₄H₈O₂ shows a strong absorption at 1740 cm⁻¹ and a broad absorption between 2500 and 3300 cm⁻¹. Explain how this information can be used to identify the…
  16. Describe5 marksStandardA student separates a mixture of amino acids using paper chromatography. The stationary phase is a sheet of cellulose paper, and the mobile phase is a non-polar solvent. The student marks a baseline in pencil near the…
  17. Compare5 marksStandardThe infrared spectra of two organic compounds, A and B, are recorded. The table shows the key absorption bands and their intensities. Compound Absorption bands / cm^-1 (appearance) A 2950 (weak), 3200–3500 (strong…
  18. Compare5 marksStandardA colourless organic compound has the molecular formula C3H6O2. Its infrared spectrum shows a strong, broad absorption between 2500 and 3300 cm^-1, and a strong, sharp absorption at about 1710 cm^-1. Compare the…
  19. Describe5 marksStandardA student records the carbon-13 NMR spectrum of propanone, CH3COCH3, and observes the number of peaks in the spectrum. Describe what the carbon-13 NMR spectrum of propanone would show, and explain your reasoning.
  20. Explain4 marksStandardA sample containing three organic compounds is separated by gas-liquid chromatography. The chromatogram shows three peaks. The first peak has a retention time of 1.8 minutes and the third peak has a retention time of…
  21. Compare5 marksStandardA student separates a mixture of two dyes, P and Q, using thin-layer chromatography. Two separate plates are run, one with a non-polar solvent and one with a polar solvent. The table shows the Rf values obtained. Dye…
  22. Explain4 marksStandardA compound with molecular formula C3H6Cl2 produces a carbon-13 NMR spectrum with two distinct peaks. Explain what this observation indicates about the carbon environments in the molecule, and suggest two possible…
  23. Describe5 marksStandardThe mass spectrum of butane, C4H10, shows a molecular ion peak at m/e = 58. The two most abundant fragment peaks are at m/e = 29 and m/e = 43. Describe what the molecular ion peak tells you about the molecule, and…
  24. Explain4 marksStandardA student uses thin-layer chromatography (TLC) to separate pigments extracted from a plant leaf. The stationary phase is aluminium oxide on a glass plate. The mobile phase is a mixture of ethanol and hexane. Two…
  25. Compare5 marksStandardA mixture of three organic compounds, X, Y, and Z, is analysed by gas-liquid chromatography using a non-polar stationary phase and an inert carrier gas. The table shows the retention times and relative peak areas…
  26. Suggest4 marksStandardA sample of a perfume is analysed by gas–liquid chromatography. The chromatogram shows four peaks. The peak areas are: P, 1.8 cm²; Q, 3.6 cm²; R, 0.6 cm²; S, 2.4 cm². The retention times are: P, 1.2 min; Q, 2.5 min; R…
  27. Suggest4 marksStandardA student separates a mixture of two coloured dyes, P and Q, using column chromatography. The column is packed with aluminium oxide, a polar stationary phase, and the dyes are eluted with a non-polar solvent. The…
  28. Explain4 marksStandardThe 1H NMR spectrum of propan-1-ol (CH3CH2CH2OH) is obtained using CDCl3 as solvent and TMS as reference. The spectrum displays four signals: a triplet at δ 0.9 (integration 3H), a multiplet at δ 1.5 (integration 2H)…
  29. Explain4 marksStandardA student separates three pigments extracted from a leaf using thin-layer chromatography. The stationary phase is a thin layer of aluminium oxide on a glass plate. The mobile phase is a non-polar solvent. After the…
  30. Explain4 marksStandardA mixture of three alkanes (pentane, hexane, heptane) is analysed by gas-liquid chromatography using a non-polar stationary phase (a high boiling point alkane on a solid support) and nitrogen as the mobile phase. The…
  31. Describe7 marksChallengeA compound X has the molecular formula C5H12O. Its carbon-13 NMR spectrum (proton-decoupled) shows four peaks at chemical shifts of δ 15, 25, 50 and 80 ppm relative to TMS. Describe the carbon environments present in X…
  32. Suggest7 marksChallengeAn unknown organic compound, suspected to be an ester, is analysed by infrared spectroscopy. The spectrum shows a strong absorption at 1740 cm^-1, a strong broad absorption between 2500 and 3300 cm^-1, and a strong…
  33. Compare7 marksChallengeA mixture of two isomeric alcohols, butan-1-ol and butan-2-ol, is separated by gas-liquid chromatography. The stationary phase is a high-boiling-point non-polar liquid coated on a solid support, and the mobile phase is…
  34. Describe7 marksChallengeThe following data were obtained from a gas-liquid chromatographic analysis of a mixture of three alkanes: pentane, hexane and heptane. Alkane Retention time / min Peak area / arbitrary units pentane 2.5 45 hexane 4.8…
  35. Describe7 marksChallenge2-methylpropan-2-ol, (CH3)3COH, is a simple alcohol. Describe the expected proton NMR spectrum of this compound, including the chemical shift region and splitting pattern for each type of proton. Describe the use of…
  36. Describe7 marksChallengeThe infrared spectrum of an organic compound, Q, shows the following absorptions: a strong, broad peak at 3350 mathrmcm^-1 a strong, sharp peak at 1735 mathrmcm^-1 a medium, sharp peak at 1650 mathrmcm^-1 Describe how…
  37. Explain5 marksChallengeA plant extract is separated by chromatography on a plate coated with aluminium oxide. The solvent is a non-polar hydrocarbon. Two pigments are separated: pigment A has Rf = 0.85 and pigment B has Rf = 0.30. Explain…
  38. Describe7 marksChallengeIn an experiment using thin-layer chromatography, a mixture of three compounds A, B and C is separated. The stationary phase is aluminium oxide and the mobile phase is a non-polar solvent. The measured Rf values are: A…
  39. Explain5 marksChallengeA student records an infrared spectrum of a colourless liquid with molecular formula C3H5N. The spectrum shows a sharp, strong absorption at 2250 cm^-1 and a broad absorption between 2500 and 3300 cm^-1. No other…
  40. Describe6 marksChallengeA reaction mixture is analysed by gas–liquid chromatography using a non-polar stationary phase and nitrogen as the mobile phase. The chromatogram shows two peaks, P and Q. Peak P appears at a retention time of 2.5…
  41. Explain5 marksChallengeThe carbon-13 NMR spectrum of benzene, C6H6, shows only one peak, at about 128 ppm. Explain why the spectrum of benzene shows only one peak.
  42. Compare7 marksChallengeA compound has the molecular formula C4H8. Its carbon-13 NMR spectrum shows exactly two peaks. Compare the possible structures of this compound and explain which structure is consistent with the spectrum.
  43. Explain5 marksChallengeA mixture of three liquid organic compounds is separated by gas-liquid chromatography. The chromatograph uses a non-polar stationary phase and an unreactive gas as the mobile phase. The three compounds are butanone…
  44. Suggest7 marksChallengeA student separates the pigments from a leaf extract using thin-layer chromatography. The stationary phase is a thin layer of aluminium oxide on a glass plate. The mobile phase is a mixture of cyclohexane and ethyl…
  45. Describe6 marksChallengeA student records the infrared spectrum of ethyl ethanoate, CH3COOC2H5. The spectrum shows a strong, sharp absorption at about 1740 cm⁻¹ and a strong, broad absorption at about 1240 cm⁻¹. Describe how the student can…
  46. Describe7 marksChallengeThe mass spectrum of an organic compound, which contains carbon, hydrogen, and a single halogen atom, is recorded. The spectrum shows a molecular ion peak at m/e = 122 with a relative abundance of 100%. There is also…
  47. Describe6 marksChallengeA student prepares a liquid ester by reacting an alcohol with an acid. The carbon-13 NMR spectrum of the ester shows four peaks, with chemical shifts of approximately 14, 22, 60 and 170 ppm. Describe what can be…
  48. Describe6 marksChallengeA student extracts pigments from a leaf and separates them by thin-layer chromatography. The stationary phase is aluminium oxide coated on a glass plate. The student draws a pencil baseline near the bottom of the plate…
  49. Describe6 marksChallengeTetramethylsilane, (CH3)4Si, is added to the sample when a proton NMR spectrum is obtained, and its signal is assigned a chemical shift of 0 ppm. Describe the reasons for using TMS as the standard for chemical shift…