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Aldehydes and Ketones

11 free MDCAT Chemistry MCQs on Aldehydes and Ketones (PM&DC syllabus), each with the answer, an explanation and the textbook line it comes from. Tap to check, no sign-up.

MDCAT (Pakistan)ChemistryPre-medical (Grade 12)11 questions

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  1. Question 1

    Low molecular weight aldehydes and ketones are water soluble up to:

    Show answer and explanation

    Answer: A) C4

    From C5 onward they are usually insoluble; formaldehyde is highly soluble. Source: Chemistry 12 KPK (taleem360.com), p. 271.

  2. Question 2

    The functional group of aldehydes, -CHO, is called the:

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    Answer: A) Formyl group

    The ketone functional group is the keto group. Source: Chemistry 12 KPK (taleem360.com), p. 265.

  3. Question 3

    Products with a carbon-nitrogen double bond, formed when primary amines react with aldehydes or ketones, are:

    Show answer and explanation

    Answer: D) Imines

    The unstable addition product loses water. Source: Chemistry 12 KPK (taleem360.com), p. 282.

  4. Question 4

    The carbon atom of the carbonyl group is:

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    Answer: B) sp2 hybridized

    Both carbon and oxygen of C=O are sp2 hybridized; the geometry is trigonal planar. Source: Chemistry 12 KPK (taleem360.com), p. 272.

  5. Question 5

    Formaldehyde gives an addition product with methylmagnesium iodide which on hydrolysis gives:

    Show answer and explanation

    Answer: A) Ethyl alcohol

    HCHO + CH3MgI -> CH3CH2OMgI -> CH3CH2OH, a primary alcohol. Source: Chemistry 12 KPK (taleem360.com), p. 236.

  6. Question 6

    The IUPAC name of formaldehyde (HCHO) is:

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    Answer: A) Methanal

    The -e of the alkane is replaced by -al. Source: Chemistry 12 KPK (taleem360.com), p. 267.

  7. Question 7

    Lower aldehydes and ketones dissolve in water because their carbonyl oxygen:

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    Answer: B) Hydrogen bonds with water

    They cannot hydrogen-bond among themselves, having no H on oxygen. Source: Chemistry 12 KPK (taleem360.com), p. 271.

  8. Question 8

    Aldehydes and ketones have boiling points:

    Show answer and explanation

    Answer: C) Above alkanes, below alcohols

    The polar C=O raises boiling points, but they cannot hydrogen-bond like alcohols. Source: Chemistry 12 KPK (taleem360.com), p. 271.

  9. Question 9

    In acid-catalysed nucleophilic addition to a carbonyl compound, the acid:

    Show answer and explanation

    Answer: B) Protonates the carbonyl oxygen

    The oxonium ion makes the carbonyl carbon more electrophilic, so weak nucleophiles can attack. Source: Chemistry 12 KPK (taleem360.com), p. 276.

  10. Question 10

    Ketones are less reactive than aldehydes towards nucleophiles partly because the ketone has a:

    Show answer and explanation

    Answer: C) More crowded carbonyl carbon

    Steric hindrance, plus two electron-releasing alkyl groups reduce the positive charge on carbon. Source: Chemistry 12 KPK (taleem360.com), p. 277.

  11. Question 11

    At room temperature, formaldehyde is a:

    Show answer and explanation

    Answer: C) Gas

    Other aldehydes are colourless liquids. Source: Chemistry 12 KPK (taleem360.com), p. 271.

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