Aldehydes, Ketones and Carboxylic Acids Mock Test – Class 12 Chemistry

1. In the Cannizzaro reaction of benzaldehyde, the oxidation number of the aldehydic carbon is approximately . What are its oxidation numbers in benzoate ion and benzyl alcohol, respectively?

2. Two isomeric ketones have the same molecular formula. One is highly branched, while the other has a less-branched carbon skeleton. The less-branched ketone will generally have the higher boiling point because it:

3. An unknown compound gives a precipitate with -DNPH, restores the magenta colour of Schiff reagent, gives a silver mirror with Tollens reagent, and gives no yellow precipitate with iodine and alkali. Among the following, the most plausible compound is:

4. Which sequence correctly represents the principal stages of the Cannizzaro mechanism?

5. Acetophenone, , is reduced under Clemmensen conditions using of zinc and of hydrochloric acid. Use

After complete carbonyl reduction, excess zinc reacts with the remaining acid according to

Ethylbenzene is isolated in yield. Which pair gives its mass and the volume of hydrogen evolved at and ? Use .

6. The number of symmetrical saturated acyclic ketones with molecular formula is:

7. A sample of propene at STP undergoes complete reductive ozonolysis. What is the total amount of carbonyl products formed?

8. The table proposes roles for four carbonyl compounds under ordinary aldol conditions.

Which row is correct?

9. A graph has nucleophilic-addition reactivity on the vertical axis and increasing electron donation by carbonyl substituents on the horizontal axis. The expected overall trend is:

10. Why is thionyl chloride often preferred over phosphorus pentachloride for preparing a pure acyl chloride from a carboxylic acid?

11. Match each ketone in Column I with its classification in Column II.

12. During acid-catalysed addition of a weak neutral nucleophile to an aldehyde, the step that directly activates the carbonyl group is:

13. Read the reaction record below and answer the question.
Ozonolysis of an alkene followed by reductive work-up gives methanal and propanone. The propanone fraction is isolated and reduced with sodium borohydride.
Which pair identifies the original alkene and the final reduction product?

14. The common name -dibromobutyraldehyde corresponds to the IUPAC name:

15. A mixture of propanal and propanone is treated with of acidified dichromate. Only propanal is oxidised under the stated conditions, and one mole of dichromate oxidises three moles of propanal. The propanoic acid is isolated in yield. Which pair gives the mole percentage of propanal in the original mixture and the isolated acid mass?

16. Match each property in Column I with its most suitable explanation in Column II.

17. Aniline does not undergo ordinary Friedel-Crafts acylation smoothly with mainly because:

18. Which row correctly classifies all the compounds shown?

19. A reaction mixture initially contains methanal, benzaldehyde, and sodium hydroxide. Assume the following ideal sequence:
First, methanal undergoes selective crossed Cannizzaro reaction with an equal amount of benzaldehyde.
Then, the remaining sodium hydroxide causes self-Cannizzaro reaction of the remaining benzaldehyde.
Benzyl alcohol is isolated in yield. Which pair gives the isolated benzyl alcohol mass and the mass of benzaldehyde left unreacted?

20. Consider the following statements about carboxylic-acid dimerisation.
Statement I: Dimerisation is especially important in vapour and non-polar media.
Statement II: A cyclic dimer contains two hydrogen bonds.
Statement III: Dimerisation helps explain the unusually high boiling points of carboxylic acids.
Statement IV: Dimerisation decreases the effective intermolecular attraction between acid molecules.

21. Why does benzoic acid generally resist an ordinary Friedel-Crafts alkylation or acylation?

22. Which use is correctly associated with methanoic acid?

23. Match each compound in Column I with its description in Column II.

24. Which row correctly relates the alcohol, oxidation condition, and main organic product?

25. The reagent commonly recognised for converting a primary alcohol into an aldehyde without extensive over-oxidation is:

26. Assertion: Ethanoic acid and methyl methanoate are functional isomers.
Reason: Both compounds have the molecular formula , but one contains and the other contains .

27. A sample gives brisk effervescence with sodium bicarbonate and also reduces Tollens reagent. Which conclusion is safest?

28. A hydrogen cyanide solution has density and contains by mass. It reacts with of an ethanal sample that is pure. If the isolated cyanohydrin yield is , what mass of ethanal cyanohydrin is obtained?

29. Assertion: Many aldehydes rapidly produce a pink or magenta colour with Schiff reagent.
Reason: Ordinary ketones generally remain negative or react much more slowly under the same test conditions.

30. An sample containing butan--one is oxidised according to:

The oxidising agent supplies of . If ethanoic acid is isolated in yield, which pair gives the isolated acid mass and the mass of unreacted butan--one?

31. An ethanal molecule labelled with at its carbonyl carbon acts only as the electrophilic acceptor in an aldol reaction. An unlabelled ethanal molecule forms the enolate donor. In the product , the labelled carbon becomes:

32. Sulphonation of benzoic acid principally introduces the group at which position relative to ?

33. Consider the following statements about ketone nomenclature.
Statement I: The parent chain must contain the carbonyl carbon.
Statement II: The carbonyl group receives the lowest possible locant before ordinary alkyl substituents are considered.
Statement III: A ketone group is expressed by the prefix when a higher-priority functional group supplies the suffix.

34. Assertion: Nucleophilic addition to a carbonyl group involves movement of the carbon-oxygen pi electrons toward oxygen.
Reason: Carbon cannot normally retain the original pi bond while also forming an additional bond to the attacking nucleophile without exceeding its usual valency.

35. Which compound is expected to be the strongest acid?

36. Use the arrangement described below: a four-carbon open chain has a group at each end and a bond between the two middle carbons. The molecular structure is:

37. A model shows the carbonyl carbon bonded to oxygen and two other atoms. The three sigma bonds lie in one plane, while electron density occurs above and below that plane. The electron density above and below the plane represents:

38. Acetamide labelled with , , undergoes complete acidic hydrolysis. Where is the isotope found?

39. An unknown -haloethanoic acid has concentration and equilibrium pH . The reference values are:


Which halogen is present?

40. Propanenitrile is to be converted into propan--ol through an aldehyde. Which sequence is appropriate?

41. A compound with molecular formula gives a -DNPH precipitate and a positive iodoform test but does not reduce Tollens reagent. Reduction of the compound gives propan--ol. Which compound and reducing reagent fit the evidence?

42. Propene, (0.250,mathrm{mol}), undergoes reductive ozonolysis with (80.0%) conversion. The complete carbonyl-product mixture is treated with excess Tollens reagent under conditions in which methanal is completely oxidised to carbonate, and (75.0%) of the theoretical silver is recovered. In a separate experiment, the ethanal fraction gives iodoform in (90.0%) yield. Assume that one mole of methanal deposits four moles of silver, while one mole of ethanal deposits two moles of silver. Which pair gives the recovered silver mass and iodoform mass? Use (M(mathrm{Ag})=108,mathrm{g,mol^{-1}}) and (M(mathrm{CHI_3})=394,mathrm{g,mol^{-1}}).

43. Hydration of an unsymmetrical internal alkyne may give a mixture of ketones because:

44. A cyclopentane ring bears a group at ring carbon and a methyl group at the adjacent ring carbon. The compound is named:

45. The equation representing the reaction of benzoic acid with phosphorus pentachloride is:

46. Consider the following statements about Benedict and Fehling reagents.
Statement I: Both may form brick-red when reduced.
Statement II: Benedict reagent uses citrate, whereas Fehling solution uses tartrate as the principal complexing ligand.
Statement III: A positive Benedict test always proves that an unknown compound is a simple aldehyde and excludes reducing carbohydrates or other reducing substances.

47. In the general notation , the symbol represents ______.

48. Ethanal and propanal are mixed under conditions where both self-aldol and crossed-aldol additions are possible. Ignoring stereoisomers, what is the minimum number of constitutionally different beta-hydroxy aldehydes expected from the two self-additions and the two possible donor-acceptor crossed additions?

49. Which row correctly gives the products formed under the stated conditions?

50. A carbonyl compound is required as a solvent that is completely miscible with water and also dissolves many organic substances. The most suitable choice is: