Free Aldehydes and Ketones MCQs with Answers
679 Aldehydes and Ketones MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Aldehydes and ketones contain the polar carbonyl group, but aldehydes are generally more readily oxidised and more reactive than ketones. Coverage includes preparation by oxidation or reduction routes, nucleophilic addition of reagents such as hydrogen cyanide and bisulfite, and tests that distinguish aldehydes from ketones.
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679 questions · page 3 of 34
- A. Tollen's reagent
- B. Iodoform test
- C. Schiff's test
- D. Benedict's reagent
Explanation: A dimethyl ketone is acetone, CH3COCH3, which contains the CH3CO- group required for the iodoform test.
Correct answer: Iodoform test- A. Ethanol
- B. Ethanal
- C. Propane
- D. Propanol
Explanation: Clemmensen reduction uses zinc amalgam and concentrated HCl to replace the carbonyl oxygen of a ketone with two hydrogen atoms.
Correct answer: Propane- A. Iodoform test
- B. Lucas test
- C. Benedict's test
- D. Tollen's test
Explanation: Acetaldehyde gives the iodoform test because it contains the CH3CO- equivalent, and it gives Benedict's and Tollens' tests because it is…
Correct answer: Lucas test- A. Acetone
- B. Acetaldehyde
- C. Acetic acid
- D. Methyl acetate
Explanation: Schiff's reagent is decolorized by sulphurous acid and develops a pink or magenta colour with aldehydes, such as acetaldehyde.
Correct answer: Acetaldehyde- A. Acetone
- B. Acetic acid
- C. Acetophenone
- D. Phenyl acetate
Explanation: The structure C6H5-CO-CH3 has a carbonyl group bonded to a phenyl group and a methyl group, so it is acetophenone, an aromatic ketone.
Correct answer: Acetophenone- A. Ether
- B. Ketone
- C. Aldehyde
- D. Ester
Explanation: Acetophenone has the structure C6H5COCH3, in which the carbonyl carbon is bonded to two carbon groups, phenyl and methyl.
Correct answer: Ketone- A. HCHO
- B. C6H5CHO
- C. Cl3CCHO
- D. CH3COCH3
Explanation: Aldol condensation requires a carbonyl compound with at least one alpha hydrogen, which allows enolate formation.
Correct answer: CH3COCH348. On heating aldehydes with Fehlings solution we get a precipitate whose colour is_________________?
- A. pink
- B. black
- C. yellow
- D. brick red
Explanation: Aldehydes reduce the blue Cu2+ ions in Fehling's solution to insoluble Cu2O, which forms a brick-red precipitate, while the aldehyde is…
Correct answer: brick red- A. HCOX
- B. CX4
- C. CHX3
- D. CH3X
Explanation: A haloform has one hydrogen and three halogen atoms attached to the same carbon, so its general formula is CHX3, where X may be Cl, Br or…
Correct answer: CHX3- A. formaldehyde
- B. acetaldehyde
- C. diemthyl ketone
- D. propionaldehyde
Explanation: Aldol condensation requires an alpha hydrogen to form an enolate or enol, but formaldehyde has no alpha carbon and therefore cannot…
Correct answer: formaldehyde- A. nucleophile addition
- B. polymerization
- C. oxidation
- D. all of the above
Explanation: Aldehydes and ketones can undergo nucleophilic addition at the carbonyl group, and some carbonyl compounds can polymerize; oxidation is…
Correct answer: all of the above- A. sp hybridized
- B. sp2 hybridized
- C. cp3 hybridized
- D. dsp2 hybridized
Explanation: The carbonyl carbon forms three sigma bonds and has no lone pair involved in its hybrid orbitals, giving it trigonal planar geometry and…
Correct answer: sp2 hybridized- A. methanol
- B. ethanal
- C. propanal
- D. hexanone
Explanation: Hexanone has the largest carbon skeleton and molar mass among the choices, so its stronger dispersion forces give it the highest boiling…
Correct answer: hexanone- A. ethanol and methanol
- B. acetaldehyde and methanal
- C. acetone and diethyl ketone
- D. all of the above
Explanation: The iodoform test is positive for ethanol and compounds containing the CH3CO- or CH3CH(OH)- group, including acetaldehyde and acetone.
Correct answer: all of the above55. Cannizaros reaction takes place through the transfer of ____________________ from complex anion?
- A. hydrogen ion
- B. hydride ion
- C. oxide ion
- D. methoxide ion
Explanation: In the Cannizzaro reaction, one aldehyde molecule is oxidized while another is reduced through transfer of a hydride ion, H-, from an…
Correct answer: hydride ion- A. proton
- B. H+
- C. both A & amp; B
- D. H-
Explanation: The tetrahydroborate ion, BH4-, supplies hydride, H-, which attacks the carbonyl carbon and reduces aldehydes or ketones to alcohols.
Correct answer: H-- A. formation of phenolic resins
- B. formation of mirror
- C. antiseptic inhalant
- D. formation of throat lozenges
Explanation: Acetaldehyde is used for silvering mirrors because it reduces silver ions to metallic silver, and it is also associated with…
Correct answer: formation of throat lozenges- A. in silvery mirror
- B. in making medicine urotropine
- C. in making throat lozenges
- D. in making acetic acid
Explanation: Formaldehyde can be used in silvering mirrors and in preparing urotropine, while its antiseptic action supports some medicinal uses such…
Correct answer: in making acetic acid- A. alkyl groups are electron donating
- B. steric hindrance
- C. Both A and B
- D. none
Explanation: Ketones are less reactive because two alkyl groups donate electron density toward the carbonyl carbon, reducing its positive character…
Correct answer: Both A and B- A. formaldehyde
- B. acetaldehyde
- C. benzaldehyde
- D. trimethyl acetaldehyde
Explanation: Cannizzaro reaction is shown by aldehydes that do not have an alpha hydrogen.
Correct answer: acetaldehyde