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 5 of 34
- A. Propan-1-ol
- B. Propan-2-ol
- C. Ethanol
- D. 2-Methylpropan-2-ol
Explanation: The nucleophilic methyl group from the Grignard reagent adds to the carbonyl carbon of acetaldehyde.
Correct answer: Propan-2-ol- A. Acetal
- B. Ketal
- C. Ether
- D. Ester
Explanation: In the presence of an acid catalyst, an aldehyde reacts with two equivalents of an alcohol.
Correct answer: Acetal- A. Iodoform test
- B. Lucas test
- C. Tollens' test
- D. Benedict's test
Explanation: Tollens' test, also known as the silver mirror test, is a classic method to differentiate aldehydes from ketones.
Correct answer: Tollens' test- A. Primary alcohol
- B. Secondary alcohol
- C. Tertiary alcohol
- D. Alkenes
Explanation: Sodium borohydride (NaBH₄) is a common reducing agent that delivers a hydride ion (H⁻) to the carbonyl carbon.
Correct answer: Secondary alcohol- A. LiAlH₄
- B. H₂/Pd
- C. Zn(Hg) and conc. HCl
- D. N₂H₄, KOH/ethylene glycol
Explanation: The Clemmensen reduction is a specific chemical reaction used to reduce aldehydes or ketones to alkanes (C=O →CH₂).
Correct answer: Zn(Hg) and conc. HCl- A. Acidic
- B. Basic
- C. Neutral
- D. Anhydrous
Explanation: The Wolff-Kishner reduction is a chemical reaction that reduces aldehydes and ketones to their corresponding hydrocarbons.
Correct answer: Basic- A. Acetaldehyde
- B. Propanal
- C. Benza ldehyde
- D. Acetone
Explanation: The Cannizzaro reaction is a disproportionation reaction given by aldehydes that do not have any α-hydrogen atoms.
Correct answer: Benza ldehyde- A. β-Hydroxy aldehyde or ketone
- B. α-Hydroxy aldehyde or ketone
- C. α,β-Unsaturated aldehyde or ketone
- D. A dicarboxylic acid
Explanation: The aldol reaction involves the nucleophilic addition of an enolate ion to another carbonyl compound.
Correct answer: β-Hydroxy aldehyde or ketone- A. Pentan-3-one
- B. Benzaldehyde
- C. Propanal
- D. Acetone
Explanation: The iodoform test is a qualitative test for the presence of a methyl ketone group (CH₃-CO-) or an alcohol that can be oxidized to a methyl…
Correct answer: Acetone- A. Aromatic aldehydes
- B. Aliphatic aldehydes
- C. Ketones
- D. Alcohols
Explanation: Fehling's test is used to differentiate between aldehydes and ketones. It is a weak oxidizing agent that gives a positive result (a red…
Correct answer: Aliphatic aldehydes- A. 2,2-Dichloropropane
- B. 1,2-Dichloropropane
- C. Propanoyl chloride
- D. Chloroacetone
Explanation: Phosphorus pentachloride (PCl₅) is a reagent that can replace a carbonyl oxygen atom with two chlorine atoms.
Correct answer: 2,2-Dichloropropane- A. One molecule of alcohol with an aldehyde
- B. Two molecules of alcohol with an aldehyde
- C. One molecule of alcohol with a ketone
- D. Two molecules of alcohol with a ketone
Explanation: A hemiacetal is a functional group that has both a hydroxyl (-OH) group and an alkoxy (-OR) group attached to the same carbon atom.
Correct answer: One molecule of alcohol with an aldehyde- A. 2-Propanone
- B. 3-Propanone
- C. 2-Butanone
- D. 2-Pentanone
Explanation: Acetone has the structure CH₃-CO-CH₃, a three-carbon ketone. The carbonyl group is on the second carbon, so the IUPAC name is 2-propanone.
Correct answer: 2-Propanone- A. Halogenated
- B. Dehydrated
- C. Oxidized
- D. Unchanged
Explanation: The Cannizzaro reaction is a redox disproportionation reaction that occurs with aldehydes lacking α-hydrogens in the presence of a strong…
Correct answer: Oxidized- A. A strong acid
- B. A strong base
- C. A strong oxidizing agent
- D. A strong reducing agent
Explanation: An enolate ion is formed by the removal of an α-hydrogen (a proton) from a carbonyl compound.
Correct answer: A strong base- A. Alcohols
- B. Ethers
- C. Ketones
- D. Aldehydes
Explanation: Schiff's test is a chemical test used to detect the presence of aldehydes.
Correct answer: Aldehydes- A. Prop-2-enal
- B. But-2-enal
- C. Pent-2-enal
- D. Propanal
Explanation: Acrolein has a three-carbon chain. It contains an aldehyde group (which gets priority and is at carbon 1) and a double bond starting at…
Correct answer: Prop-2-enal- A. H2SO4
- B. HSO4
- C. SO3H+
- D. SO3
Explanation: In aromatic sulfonation, SO₃ acts as the electrophile that attacks the benzene ring to form the sulfonic acid.
Correct answer: SO3- A. Aromatic aldehydes
- B. Ketones
- C. Reducing sugars (which contain an aldehyde or α-hydroxy ketone group)
- D. Non-reducing sugars
Explanation: Benedict's test is a chemical test used to detect reducing sugars. These sugars typically have a free aldehyde group or an α-hydroxy…
Correct answer: Reducing sugars (which contain an aldehyde or α-hydroxy ketone group)- A. CH₂=C(OH)CH₃
- B. CH₃CH=CHOH
- C. CH₂=CH-O-CH₃
- D. HOCH₂-CH=CH₂
Explanation: Tautomerization of acetone involves the removal of a proton from one of the α-carbons and its placement on the carbonyl oxygen, along with…
Correct answer: CH₂=C(OH)CH₃