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 4 of 34
- A. CH3-CHO
- B. CH3-CH-CH3
- C. CH3-COOH
- D. CH3-CO-CH2-CH3
Explanation: Tollens reagent oxidizes aldehydes to carboxylate ions while Ag+ is reduced to metallic silver, producing the characteristic silver…
Correct answer: CH3-CHO- A. acetaldehyde
- B. ethyl alcohol
- C. methyl alcohol
- D. acetone
Explanation: The iodoform test is positive for compounds containing the CH3CO group, and ethanol is oxidized under the test conditions to ethanal…
Correct answer: methyl alcohol- A. reaction with HCN
- B. reaction with NaHSO3
- C. reaction with 2 4 dinitrophenyl hydrazine
- D. reaction with Fehling solution
Explanation: Ketones form addition products with HCN and NaHSO3 and condensation products with 2,4-dinitrophenylhydrazine because their carbonyl group…
Correct answer: reaction with Fehling solution- A. Ethanal
- B. Acetone
- C. Benzaldehyde
- D. Butanone
Explanation: Aldol condensation requires at least one alpha hydrogen so that an enolate can form.
Correct answer: Benzaldehyde- A. alkaline aquenous iodine
- B. aqueous bromine
- C. Fehling solution
- D. aqueous NaOH
Explanation: Acetone contains the CH3CO- group and gives the iodoform test with alkaline aqueous iodine, producing yellow iodoform, CHI3.
Correct answer: alkaline aquenous iodine- A. Addition - elimination
- B. Electrophilic addition
- C. Free radical addition
- D. Nucleophilic addition
Explanation: The given reaction involves the addition of a nucleophile (NH3) to a carbonyl group of an aldehyde (CH3CHO) to form an imine.
Correct answer: Nucleophilic addition- A. Aqueous Bromine
- B. Fehling's reagent
- C. Tollen's reagent
- D. Alkaline aqueous iodine
Explanation: Propanone (also known as acetone) is a ketone that is often produced in the breath of diabetic patients.
Correct answer: Alkaline aqueous iodine- A. Green
- B. Brown
- C. Magenta
- D. Red
Explanation: Brady's reagent (2,4-dinitrophenylhydrazine) reacts with the carbonyl group of benzaldehyde.
Correct answer: Red- A. Because water reacts violently with LiAlH4
- B. Because water will protonate LiAlH4
- C. Because water inhibits the process
- D. Because it will result to alkenes
Explanation: This is the correct option. LiAlH₄ is a highly reactive reducing agent.
Correct answer: Because water reacts violently with LiAlH4- A. Methanal
- B. Ethanal
- C. Propanal
- D. Butanal
Explanation: Acetaldehyde is a common name. The IUPAC name is based on the longest carbon chain; with two carbon atoms, the parent alkane is ethane.
Correct answer: Ethanal- A. Formaldehyde
- B. Acetone
- C. Benzaldehyde
- D. Acetaldehyde
Explanation: 2-Propanone is the systematic IUPAC name for the simplest ketone. Its widely used common name is acetone.
Correct answer: Acetone- A. Acetaldehyde
- B. Propanal
- C. Benzaldehyde
- D. Cyclohexanone
Explanation: An aromatic aldehyde is a compound where an aldehyde functional group (-CHO) is attached directly to an aromatic ring.
Correct answer: Benzaldehyde- A. 2-Methyl-3-butanone
- B. 3-Methyl-2-butanone
- C. Isobutyl methyl ketone
- D. 2-Pentanone
Explanation: The longest carbon chain containing the ketone is a four carbon compound (butanone).
Correct answer: 3-Methyl-2-butanone- A. Acetic acid
- B. Formaldehyde
- C. Formic acid
- D. Acetone
Explanation: Formalin is the common name for a saturated aqueous solution of formaldehyde, typically containing 37-40% formaldehyde by mass.
Correct answer: Formaldehyde- A. sp hybridized
- B. sp² hybridized
- C. sp³ hybridized
- D. unhybridized
Explanation: The carbon atom in a carbonyl group (C=O) forms three sigma bonds and one pi bond.
Correct answer: sp² hybridized- A. Propanal
- B. Propan-1-ol
- C. Propane
- D. Ethoxyethane
Explanation: Propan-1-ol can form strong intermolecular hydrogen bonds due to its -OH group.
Correct answer: Propan-1-ol- A. They are non-polar
- B. They can form hydrogen bonds with water
- C. They have low molecular weights
- D. They can ionize in water
Explanation: The lone pairs of electrons on the oxygen atom of the carbonyl group can act as hydrogen bond acceptors.
Correct answer: They can form hydrogen bonds with water- A. CH3CHO
- B. CH3COCH3
- C. CH3COCH2CHO
- D. CH3COCH2COOCH3
Explanation: The acidity of α-hydrogens increases with electron withdrawing groups adjacent to the α-carbon.In CH₃COCH₂COOCH₃, the α -hydrogens are…
Correct answer: CH3COCH2COOCH3- A. Two molecules of formaldehyde
- B. Two molecules of acetaldehyde
- C. One molecule of acetaldehyde and one of formaldehyde
- D. One molecule of propanal
Explanation: Reductive ozonolysis cleaves the carbon-carbon double bond and forms a carbonyl group on each of the original double-bonded carbons.
Correct answer: Two molecules of acetaldehyde- A. Electrophilic substitution
- B. Nucleophilic addition
- C. Electrophilic addition
- D. Nucleophilic substitution
Explanation: This is a classic nucleophilic addition reaction. The nucleophilic cyanide ion (CN⁻) attacks the partially positive (electrophilic) carbon…
Correct answer: Nucleophilic addition