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CAIE A Level Chemistry 9701

Carbonyl compounds questions

Exam-style questions on Carbonyl compounds, 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 marksStandardCompare the reduction of propanal and propanone using NaBH4. In your answer, name the organic product formed in each case and state the conditions required.
  2. Compare5 marksStandardTwo organic compounds, butanone and propanal, are each treated with alkaline aqueous iodine. Compare the expected observations for the two compounds and explain the difference in terms of their structures.
  3. Explain4 marksStandardExplain why propanal is oxidised by acidified K2Cr2O7 under reflux to give propanoic acid, but propanone is not oxidised under the same conditions.
  4. Describe5 marksStandardA colourless liquid is suspected to be a carbonyl compound. A student adds a few drops of 2,4-dinitrophenylhydrazine (2,4-DNPH) reagent to a sample of the liquid. Describe what the student would observe if the liquid…
  5. Explain4 marksStandardPropanone reacts with hydrogen cyanide in the presence of potassium cyanide to form a hydroxynitrile. Explain the mechanism of this reaction, including the role of the cyanide ion.
  6. Compare5 marksStandardCompare the reactions of aldehydes and ketones with Tollens' reagent and with hydrogen cyanide (in the presence of KCN catalyst). In your answer, include typical observations and explain any differences in reactivity…
  7. Suggest4 marksStandardA laboratory has two unlabelled samples, each a colourless liquid. One is propanal and the other is propanone. A student adds a few drops of each liquid to separate warm Fehling's solution. Suggest what the student…
  8. Explain4 marksStandardA student plans to prepare the aldehyde ethanal by oxidising ethanol. The student heats a mixture of ethanol and acidified potassium dichromate(VI) under reflux. Explain why the student will not obtain ethanal as the…
  9. Compare5 marksStandardTwo isomeric carbonyl compounds, butanone and butanal, are each treated separately with alkaline aqueous iodine. Compare the results of this test for the two compounds, and explain the difference.
  10. Explain4 marksStandardPropanone reacts with hydrogen cyanide, HCN, to form a hydroxynitrile. A small amount of KCN is added as a catalyst. Explain the role of the KCN in this reaction.
  11. Explain4 marksStandardPropanone reacts with hydrogen cyanide to form 2-hydroxy-2-methylpropanenitrile. CH3COCH3 + HCN → (CH3)2C(OH)CN The reaction is very slow if hydrogen cyanide is used alone, but it proceeds readily when potassium…
  12. Describe5 marksStandardA colourless liquid was thought to be an organic compound containing a carbonyl group. Describe how 2,4-dinitrophenylhydrazine (2,4-DNPH) reagent could be used to show that the liquid contains a carbonyl group, and…
  13. Suggest4 marksStandardA student plans to prepare propanone by oxidising propan-2-ol. Suggest the reagent, the conditions, and the reason why propanone is not further oxidised under these conditions.
  14. Describe5 marksStandardA student heats ethanol with an excess of acidified potassium dichromate(K2Cr2O7) solution and distils off the product as it forms. The product is collected and tested to confirm its identity.
  15. Suggest4 marksStandardA student wants to prepare propanone from propan-2-ol in the laboratory. Suggest the reagents and conditions needed for this preparation, and explain why the product is propanone rather than an aldehyde.
  16. Explain4 marksStandardPropan-2-ol is heated under reflux with acidified potassium dichromate. The organic product is propanone. Explain, in terms of the structure of propan-2-ol and of propanone, why propanone is formed rather than propanal.
  17. Explain4 marksStandardA student carries out tests on two carbonyl compounds, P and Q, both with the molecular formula C4H8O. The results are shown. Test P Q Tollens' reagent silver mirror formed no change Fehling's solution red precipitate…
  18. Compare5 marksStandardA student is given a sample of butanone, CH3COCH2CH3. The student adds alkaline iodine solution, I2(aq) with NaOH, and warms the mixture. A yellow precipitate forms. Compare the reaction of butanone with the reaction…
  19. Describe5 marksStandardEthanol is oxidised by heating with an excess of acidified potassium dichromate(VI) and distilling off the product as it forms. The organic product, compound X, is a colourless liquid. (a) State the identity of…
  20. Compare5 marksStandardA student has two unlabelled samples, one of butanone and one of butanal. Describe how the student could use the reaction with alkaline iodine (iodoform test) and the reaction with Tollens' reagent to distinguish…
  21. Describe5 marksStandardA student is given a colourless liquid that is known to be a carbonyl compound. Describe how the student could confirm the presence of a carbonyl group using 2,4-dinitrophenylhydrazine (2,4-DNPH) reagent, and state the…
  22. Compare5 marksStandardA student oxidises two separate samples of propan-1-ol and propan-2-ol using acidified potassium dichromate(K2Cr2O7) and distillation. Compare the products formed and the ease of oxidation of these two alcohols. In…
  23. Compare5 marksStandardCompare the oxidation of propan-1-ol with the oxidation of propan-2-ol using acidified K2Cr2O7 and distillation. Include in your answer the organic product formed in each case and the conditions needed to obtain that…
  24. Suggest4 marksStandardA student has two unlabelled bottles, one containing propanal and the other containing propanone. Suggest how the student could use Fehling's reagent to identify which bottle contains propanal. Explain the result…
  25. Explain4 marksStandardPropanone reacts with hydrogen cyanide, HCN, in the presence of KCN as a catalyst, to form a hydroxynitrile. Explain, in terms of the mechanism of the reaction, why the product is formed as a racemic mixture.
  26. Describe5 marksStandardA student is given a colourless liquid P. A few drops of P are added to a solution of 2,4-dinitrophenylhydrazine (2,4-DNPH reagent). An orange precipitate forms immediately. Describe how the student can use this…
  27. Suggest4 marksStandardA student has two colourless liquids, propanal and propanone, in unlabelled bottles. Suggest how the student could use Fehling's reagent to distinguish between them, and state the observation that would identify each…
  28. Suggest4 marksStandardA student wants to convert propan-2-ol into propanone. Suggest the reagent and conditions needed for this conversion.
  29. Describe5 marksStandardA student oxidises ethanol by heating it with acidified potassium dichromate(K2Cr2O7) and distilling off the product as it forms. The distillate is collected and tested with 2,4-dinitrophenylhydrazine (2,4-DNPH)…
  30. Explain4 marksStandardPropanone reacts with hydrogen cyanide, HCN, in the presence of potassium cyanide, KCN, and heat to form a hydroxynitrile. Explain why the reaction of propanone with hydrogen cyanide is described as a nucleophilic…
  31. Suggest5 marksChallengeA colourless liquid, X, has the molecular formula C3H6O. It reacts with 2,4-dinitrophenylhydrazine reagent to form an orange precipitate, but it does not react with Tollens' reagent. Suggest two chemical tests, other…
  32. Describe6 marksChallengeA student oxidises ethanol to ethanal using acidified potassium dichromate(VI). The reaction mixture is heated and the product is collected by distillation. Describe the essential practical conditions needed to obtain…
  33. Describe5 marksChallengeA student plans to convert ethanol into ethanal by oxidation, using acidified potassium dichromate(VI). Describe the procedure that the student should use to obtain ethanal as the main organic product, and explain why…
  34. Suggest6 marksChallengeA laboratory has two unlabelled bottles, each containing a colourless liquid. One is propanal and the other is propanone. Suggest how you could distinguish between the two liquids, using chemical tests only. Include…
  35. Describe6 marksChallengeA liquid suspected to be a carbonyl compound is mixed with 2,4-dinitrophenylhydrazine reagent and warmed. An orange precipitate forms. In a separate experiment, the liquid is warmed with Fehling's solution and no…
  36. Explain5 marksChallengePropanone reacts with hydrogen cyanide, using potassium cyanide as a catalyst and heat, to form a hydroxynitrile. Explain why this reaction occurs and describe the mechanism by which the product is formed.
  37. Explain6 marksChallengePropanone reacts with hydrogen cyanide, HCN, in the presence of a small amount of potassium cyanide, KCN, as a catalyst, to form a hydroxynitrile. Explain why the addition of HCN to propanone is a nucleophilic…
  38. Describe7 marksChallengePropanal and propanone are two carbonyl compounds with the molecular formula C3H6O. Describe how you would use chemical tests to distinguish between them, including reagents, conditions and expected observations.
  39. Compare6 marksChallengeButanone, CH3COCH2CH3, and butanal, CH3CH2CH2CHO, are structural isomers with the molecular formula C4H8O. Compare the reactions of the two compounds with: (a) Tollens' reagent; (b) alkaline aqueous iodine. For each…
  40. Suggest7 marksChallengeA student oxidises propan-2-ol with acidified potassium manganate(VII). The mixture is heated gently and the product is collected by distillation as it forms. The student then treats a sample of the product with…
  41. Explain7 marksChallengeA student investigates an unknown liquid, X. The student carries out the following tests. Test 1: A few drops of X are added to warm Fehling's solution. A red precipitate forms. Test 2: A few drops of X are added to a…
  42. Suggest5 marksChallengePropan-1-ol and propan-2-ol are each heated with acidified potassium dichromate(VI), K2Cr2O7(aq), and the product of each reaction is collected by distillation. The product formed from propan-1-ol is P and the product…
  43. Compare7 marksChallengeCompare the reduction of propanal and propanone with aqueous sodium borohydride, NaBH4. Include in your answer the products formed and the role of NaBH4 in the reaction.