Aldehydes and Ketones

Aldehydes and Ketones MDCAT MCQs with answers

49 past paper MCQs from Chemistry unit 17, Aldehydes and Ketones, across 3 topics. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.

Practise as a quiz

Nomenclature and Structure of Aldehydes and Ketones

1.Which of the following is the correct name of $\mathrm{CH_3CH_2CH_2COCH_2CHO}$? (MDCAT 2022)

  1. 3-oxohexanal
  2. 3-onehexanal
  3. 3-oxohexanone
  4. hexanedial
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Correct answer: (a) 3-oxohexanal

The aldehyde takes the suffix and is carbon 1, so the ketone at carbon 3 is named as an oxo prefix.

2.$\mathrm{C_nH_{2n}O}$ is the general formula of: (MDCAT 2024)

  1. ethers
  2. carboxylic acids
  3. ketones
  4. carbolic acid
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Correct answer: (c) ketones

Aldehydes and ketones share this formula; of the options only the ketones fit.

3.Formalin is a mixture of: (NUMS MDCAT 2025)

  1. 40% HCHO, 8% CH3OH, 52% H2O
  2. 40% CH3CHO, 8% CH3OH, 50% H2O
  3. 40% CH3CHO, 8% C2H5OH, 50% H2O
  4. 45% HCHO, 8% C2H5OH, 50% H2O
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Correct answer: (a) 40% HCHO, 8% CH3OH, 52% H2O

Formalin is the $40\%$ aqueous solution of formaldehyde, with a little methanol to stop it polymerizing.

All 8 Nomenclature and Structure of Aldehydes and Ketones MCQs → Nomenclature and Structure of Aldehydes and Ketones notes →

Reactions of Aldehydes and Ketones

4.Which of the following is also called the silver mirror test? (MDCAT 2022)

  1. Benedict's solution test
  2. Fehling's solution test
  3. iodoform test
  4. Tollen's reagent test
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Correct answer: (d) Tollen's reagent test

The aldehyde reduces the silver ion of Tollen's reagent to metallic silver, which plates the tube.

5.The blue colour of Fehling's solution is changed to red when warmed with an aldehyde due to the formation of: (MDCAT 2024)

  1. $\mathrm{NO_2}$
  2. $\mathrm{Cu_2O}$
  3. $\mathrm{Ag_2O}$
  4. $\mathrm{SO_2}$
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Correct answer: (b) $\mathrm{Cu_2O}$

The aldehyde reduces copper(II) to a red precipitate of copper(I) oxide.

6.The reaction of HCN with formaldehyde is a: (MDCAT 2024)

  1. nucleophilic addition reaction
  2. nucleophilic substitution reaction
  3. electrophilic addition reaction
  4. electrophilic substitution reaction
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Correct answer: (a) nucleophilic addition reaction

The cyanide ion adds to the carbon of the polar carbonyl group, giving a cyanohydrin.

All 37 Reactions of Aldehydes and Ketones MCQs → Reactions of Aldehydes and Ketones notes →

Reactivity of Aldehydes and Ketones

7.Which carbonyl carbon is more electrophilic: (SIBA MDCAT 2025)

  1. HCOOH
  2. HCHO
  3. CH3COCH3
  4. CH3COOH
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Correct answer: (b) HCHO

Formaldehyde has no alkyl group to push electrons towards the carbonyl carbon, so that carbon is the most electron poor.

8.Which aldehyde is more reactive towards nucleophilic addition? (KMU MDCAT 2024)

  1. Acetaldehyde
  2. Butyraldehyde
  3. Formaldehyde
  4. Propionaldehyde
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Correct answer: (c) Formaldehyde

Formaldehyde has no alkyl group feeding electrons to the carbonyl carbon, so it is the most open to attack.

9.Acetone is less reactive than acetaldehyde due to: (PMC MDCAT 2022)

  1. More Stearic hindrance offered by its methyl groups.
  2. Electron withdrawing nature of its methyl groups.
  3. Its Carbonyl carbon is sp2 hybridized.
  4. Oxygen of carbonyl group is more electronegative than carbon atom.
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Correct answer: (a) More Stearic hindrance offered by its methyl groups.

Two methyl groups crowd the carbonyl carbon and push electrons towards it, so it is less open to attack.

10.Both aldehydes and ketones are planer to the neighborhoods of carbonyl (C=O) group. Which one of the following bonds is distorted towards the oxygen atoms? (UHS MDCAT 2015)

  1. π-bond of C and O
  2. Sigma bond of C and H
  3. Sigma bond of C and O
  4. Sigma bond of C and C
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Correct answer: (a) π-bond of C and O

Oxygen is the more electronegative, so the loose pi electrons of the double bond are drawn towards it.

Reactivity of Aldehydes and Ketones notes →

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