What is the approximate percentage by mass of oxygen in methanal, HCHO (C = 12, H = 1, O = 16)?
Correct answer C. 53.3%
Topic / 37 questions
Aldehydes and Ketones MCQs
Aldehydes and Ketones MCQs are multiple-choice questions on carbonyl compounds, covering their naming, structure, preparation, nucleophilic addition reactions, oxidation, reduction and identification tests. They follow the MDCAT chemistry curriculum, and every question on MCQs360 shows its correct answer instantly so you can check reagents, products and calculations as you practise.
- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
What is the IUPAC name of CH₃COCH₃?
Correct answer A. Propanone
What is the hybridisation of the carbonyl carbon in aldehydes and ketones?
Correct answer C. sp²
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Oxidation of a secondary alcohol with acidified potassium dichromate gives ____.
Correct answer A. a ketone
Aldehydes are generally more reactive than ketones towards nucleophilic addition because ____.
Correct answer D. they have less steric hindrance and fewer electron-releasing alkyl groups
Ethanal reacts with HCN in the presence of a base to form ____.
Correct answer A. 2-hydroxypropanenitrile
In acid-catalysed nucleophilic addition to a carbonyl group, the acid acts by ____.
Correct answer A. protonating the carbonyl oxygen to make the carbon more electrophilic
Reduction of propanone with NaBH₄ gives ____.
Correct answer B. propan-2-ol
Which compound gives a silver mirror with Tollens’ reagent?
Correct answer B. Ethanal
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Which of these aldehydes cannot undergo aldol condensation?
Correct answer C. Methanal
Aldehydes and ketones react with 2,4-dinitrophenylhydrazine to give ____.
Correct answer D. a yellow-orange precipitate
What mass of copper(I) oxide forms when 0.05 mol of propanal reacts completely with Fehling’s solution (Cu = 63.5, O = 16)?
Correct answer C. 7.15 g
Take C = 12, H = 1, I = 127. What mass of triiodomethane, CHI₃, can form from 0.10 mol of propanone in the iodoform reaction?
Correct answer D. 39.4 g
Take molar volume = 22.4 dm³/mol. What volume of H₂ at STP is needed to reduce 11.6 g of propanone (M = 58 g/mol) completely to propan-2-ol?
Correct answer C. 4.48 dm³
Take C = 12, H = 1, O = 16. What is the percentage by mass of carbon in propanone, CH₃COCH₃?
Correct answer A. 62.1%
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Reduction of butanal with LiAlH₄ followed by aqueous work-up gives ____.
Correct answer D. Butan-1-ol
What mass of copper(I) oxide (M = 143 g/mol) forms when 0.050 mol of ethanal reacts completely with Fehling’s solution?
Correct answer C. 7.15 g
Take Ag = 108. What mass of silver is deposited when 0.10 mol of ethanal reacts completely with Tollens’ reagent?
Correct answer C. 21.6 g
Which statement about the oxidation of ketones is correct?
Correct answer D. They are oxidised only by strong oxidising agents, with breaking of C–C bonds
What is formed when propanone is reduced with sodium tetrahydridoborate(III), NaBH₄?
Correct answer A. Propan-2-ol
About Aldehydes and Ketones MCQs
Naming and preparation questions ask for IUPAC names such as propanal, the industrial manufacture of methanal from methanol, oxidation of alcohols and ozonolysis of alkenes. Reactivity questions compare aldehydes with ketones and test acid- and base-catalysed nucleophilic addition, including the addition of HCN and reactions with 2,4-dinitrophenylhydrazine. Oxidation and reduction questions cover Tollens' reagent and its active species, Fehling's solution, why ketones resist mild oxidation, the iodoform reaction for methyl ketones and reduction to primary or secondary alcohols. Several questions add mole calculations, such as the mass of silver deposited in the silver mirror test.
Key facts to remember
- The carbonyl carbon is sp² hybridised and the C=O bond is polar, so aldehydes and ketones undergo nucleophilic addition.
- Aldehydes are more reactive than ketones towards nucleophiles because they have less steric hindrance and fewer electron-donating alkyl groups.
- Tollens' reagent contains the diamminesilver(I) ion, [Ag(NH₃)₂]⁺, and gives a silver mirror with aldehydes but not with ketones.
- Compounds containing the CH₃CO– group, such as propanone and ethanal, give a yellow precipitate of triiodomethane (CHI₃) in the iodoform test.
- Reduction of aldehydes gives primary alcohols and reduction of ketones gives secondary alcohols, for example with NaBH₄ or H₂ and a nickel catalyst.
- Methanal is manufactured by oxidising methanol vapour with air over a heated silver catalyst.
Exams that include Aldehydes and Ketones MCQs
Pakistan
- MDCAT
- ECAT
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Aldehydes and Ketones MCQs
- Make a table of tests (Tollens', Fehling's, iodoform, 2,4-DNPH) showing which compounds give a positive result.
- For Tollens' calculations, remember that one mole of RCHO deposits two moles of silver.
- Explain reactivity differences using both steric and electronic effects.
- Revise ozonolysis products by splitting the C=C bond and adding an oxygen to each carbon.
Frequently asked questions
What does the MDCAT syllabus include in Aldehydes and Ketones?
The PMDC MDCAT curriculum covers the nomenclature and structure of aldehydes and ketones, their preparation, comparative reactivity, acid- and base-catalysed nucleophilic addition reactions, and their reduction to alcohols and oxidation reactions.
Which exams ask Aldehydes and Ketones MCQs?
Carbonyl chemistry is tested in MDCAT, ECAT, NUMS and AKU entry tests and in FSc board papers in Pakistan. It is also part of NEET and JEE Main in India and HSC and medical admission tests in Bangladesh.
How can an aldehyde be distinguished from a ketone?
Aldehydes are easily oxidised, so they give a silver mirror with Tollens' reagent and, for aliphatic aldehydes, a brick-red precipitate with Fehling's solution. Ketones resist mild oxidation and give neither result, although both classes give an orange-yellow precipitate with 2,4-DNPH.
Last reviewed October 2026