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 2 of 34
- A. HI
- B. LiAlH4
- C. K2Cr2O7
- D. NaBH4
Explanation: Acidified potassium dichromate is the standard oxidising agent for converting an aldehyde to a carboxylic acid, turning from orange to…
Correct answer: K2Cr2O7- A. Formaldehyde
- B. Acetaldehyde
- C. Propanal
- D. Propanone
Explanation: Reducing an aldehyde adds hydrogen across the carbonyl group and gives a primary alcohol with the same number of carbon atoms, so the one…
Correct answer: Formaldehyde- A. Electrophilic addition
- B. Nucleophilic substitution
- C. Nucleophilic addition
- D. Nucleophilic elimination
Explanation: The carbonyl group is polar, with a partially positive carbon atom that is attacked by nucleophiles, followed by addition across the C=O…
Correct answer: Nucleophilic addition- A. Electrophilic addition
- B. Electrophilic substitution
- C. Nucleophilic addition
- D. Necleophilic substitution
Explanation: The cyanide ion from HCN attacks the electrophilic carbonyl carbon of the aldehyde, followed by protonation to give a cyanohydrin, so the…
Correct answer: Nucleophilic addition- A. the presence of halogen atom
- B. the presence of magnesium atom
- C. the polarity of C-Mg bond
- D. all
Explanation: A Grignard reagent is reactive because the C-Mg bond is strongly polar, giving the carbon atom partial negative character and making it a…
Correct answer: the polarity of C-Mg bond- A. increases the nucleophilic character of reagent
- B. increases electrophilic character of carbonyl compound
- C. acidic character of reagent
- D. both a and b
Explanation: A base removes a proton from a nucleophilic reagent such as water, alcohol or a carbon compound, increasing the concentration and…
Correct answer: increases the nucleophilic character of reagent- A. Tartaric acid
- B. Propanoic acid
- C. Lactic acid
- D. Valeric acid
Explanation: Acetaldehyde cyanohydrin is CH3CH(OH)CN. Acid hydrolysis changes the nitrile group, -CN, into a carboxylic acid group, -COOH, giving…
Correct answer: Lactic acid- A. Grignard reagent
- B. Tollens reagent
- C. Fehlings reagent
- D. Benedicts reagent
Explanation: Grignard reagents add to the electrophilic carbonyl carbon of both aldehydes and ketones, producing alcohols after hydrolysis.
Correct answer: Grignard reagent- A. electronphilic addition
- B. electrophilic substitution
- C. nucleophilic addition
- D. nucleophilic substitution
Explanation: In acetone, the carbonyl carbon is electron-deficient, while cyanide ion from HCN acts as the nucleophile and attacks it, followed by…
Correct answer: nucleophilic addition- A. Acid
- B. Base
- C. Both A and B
- D. None
Explanation: Nucleophilic addition can be acid-catalysed by protonating the carbonyl oxygen, which makes the carbonyl carbon more electrophilic, or…
Correct answer: Both A and B- A. CH4
- B. C2H6
- C. C2H4
- D. C2H2
Explanation: Ethyne reacts with dilute H2SO4 in the presence of HgSO4 by acid-catalysed hydration, initially forming an enol that rearranges to…
Correct answer: C2H2- A. Carboxylic acid
- B. Acetaldehyde
- C. Formaldehyde
- D. Ketone
Explanation: Urotropine, or hexamethylenetetramine, is formed by the condensation of formaldehyde with ammonia: 6HCHO + 4NH3 → (CH2)6N4 + 6H2O.
Correct answer: Formaldehyde- A. PdCl2
- B. Cu2Cl2
- C. CuCl2
- D. PbCl2
Explanation: Industrial oxidation of ethene to ethanal by the Wacker process uses PdCl2 as the catalyst and CuCl2 as the promoter or co-oxidant.
Correct answer: CuCl2- A. 60%
- B. 50%
- C. 52%
- D. 8%
Explanation: Commercial formalin usually contains 40% formaldehyde and about 8% methanol, so water makes up the remainder: 100% - 40% - 8% = 52% water.
Correct answer: 52%- A. formamint
- B. lactomint
- C. aldomint
- D. formalactose
Explanation: Formaldehyde combined with lactose produces Formamint, a well-known antiseptic throat lozenge.
Correct answer: formamint- A. 10%
- B. 20%
- C. 40%
- D. 60%
Explanation: Formalin is conventionally a concentrated aqueous solution containing about 40% formaldehyde by mass, often stabilized with a small amount…
Correct answer: 40%- A. formaldehyde
- B. acetaldehyde
- C. methane
- D. acetone
Explanation: On dry distillation, calcium acetate undergoes ketonic decarboxylation: (CH3COO)2Ca gives CH3COCH3, acetone, along with calcium carbonate.
Correct answer: acetone- A. sp3 hybridised
- B. sp2 hybridised
- C. sp hybridised
- D. Unhybridised
Explanation: The carbonyl carbon forms three sigma bonds in a trigonal planar arrangement and has an unhybridised p orbital for the pi bond, so it is…
Correct answer: sp2 hybridised- A. White colour
- B. Yellow colour
- C. Red colour
- D. Blue colour
Explanation: HCHO reduces Fehling solution, converting blue Cu2+ ions into brick-red Cu2O precipitate while the aldehyde is oxidised to formate or…
Correct answer: Red colour- A. Aldehydes
- B. Thio alcohols
- C. Amines
- D. Ethers
Explanation: In Tollens' test, aldehydes reduce diamminesilver(I) ions to metallic silver, producing a silver mirror, while the aldehyde is oxidised to…
Correct answer: Aldehydes