Nomenclature, Structure and Preparation of Carboxylic Acids

Nomenclature, Structure and Preparation of Carboxylic Acids MDCAT MCQs with answers

22 past paper MCQs on Nomenclature, Structure and Preparation of Carboxylic Acids, from the Carboxylic Acids unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.The hydrolysis of nitriles produces: (MDCAT 2020)

  1. carboxylic acids
  2. aldehydes
  3. ketones
  4. esters
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Correct answer: (a) carboxylic acids

$\mathrm{RCN+2H_2O\to RCOOH+NH_3}$, which is one of the standard preparations of an acid.

2.When carboxylic acids and dicarboxylic acids have similar molecular weights, how do their melting points compare? (MDCAT 2022)

  1. carboxylic acids have greater melting points
  2. dicarboxylic acids have greater melting points
  3. both acids have similar melting points
  4. there is no consistent pattern
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Correct answer: (b) dicarboxylic acids have greater melting points

Two carboxyl groups make more hydrogen bonds and pack better, so more heat is needed to break the crystal up.

3.If both carboxylic acid and ketone $\mathrm{C{=}O}$ groups are present in a chain, then the final name will be given as: (MDCAT 2022)

  1. oxo...oic acid
  2. one...oic acid
  3. al...oic acid
  4. none of these
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Correct answer: (a) oxo...oic acid

The acid outranks the ketone, so the acid takes the suffix and the ketone becomes an oxo prefix.

4.If both a carboxylic acid group and a ketone group are present in a chain, then the final name will be given as: (MDCAT 2023)

  1. oxo...oic acid
  2. one...oic acid
  3. al...oic acid
  4. none of these
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Correct answer: (a) oxo...oic acid

The acid takes the suffix, so the ketone is named as an oxo prefix.

5.The common name of 2-hydroxypropanoic acid is: (MDCAT 2024)

  1. tartaric acid
  2. lactic acid
  3. phthalic acid
  4. formic acid
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Correct answer: (b) lactic acid

That is lactic acid, the acid of sour milk and of tired muscle.

6.The boiling point of carboxylic acids are relatively high due to: (NUMS MDCAT 2025)

  1. Increased molecular mass
  2. Intermolecular carbon bonding
  3. Intermolecular oxygen bonding
  4. Intermolecular hydrogen bonding
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Correct answer: (d) Intermolecular hydrogen bonding

Two molecules of the acid hydrogen bond into a dimer, so a great deal of heat is needed to separate them.

7.Common name of 2-hydroxy propanoic acid is: (UHS MDCAT 2024)

  1. Tartaric acid
  2. Lactic acid
  3. Phthalic acid
  4. Formic acid
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Correct answer: (b) Lactic acid

2-hydroxypropanoic acid is lactic acid, the acid of sour milk.

8.Acetic acid can be prepared by the hydrolysis of (KMU MDCAT 2024)

  1. Ethanal
  2. Ethanol
  3. Methanoic acid
  4. Methyl cyanide
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Correct answer: (d) Methyl cyanide

Hydrolysis of methyl cyanide gives acetic acid and ammonia.

9.Select the carboxylic acid with highest melting point: (NUMS MDCAT 2024)

  1. Ethanoic acid
  2. Propanoic acid
  3. Butanoic acid
  4. Pentanoic acid
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Correct answer: (a) Ethanoic acid

Ethanoic acid packs into the tightest crystal of the four, so it melts highest.

10.Hydrolysis of Nitriles produces: (NUMS MDCAT 2023)

  1. Carboxylic acid
  2. Aldehydes
  3. Ketones
  4. Esters
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Correct answer: (a) Carboxylic acid

A nitrile hydrolyses to the carboxylic acid with one more carbon than the alkyl group.

11.Carboxylic acids are obtained from fats and oils by: (PMC MDCAT 2022)

  1. Oxidation
  2. Reduction
  3. Decarboxylalion
  4. Hydrolysis
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Correct answer: (d) Hydrolysis

Fats and oils are esters, and hydrolysing them gives glycerol and the fatty acids.

12.Which one of the following carboxylic acid has an unpleasant smell? (PMC MDCAT 2022)

  1. Propionic acid
  2. Formic acid
  3. Butyric acid
  4. Acetic acld
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Correct answer: (c) Butyric acid

Butyric acid is what gives rancid butter its smell.

13.Acetic acid was first isolated from: (PMC MDCAT 2022)

  1. Ants
  2. Butter
  3. Milk
  4. Vinegar
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Correct answer: (d) Vinegar

Acetic acid was first got from vinegar, which is where its name comes from.

14.The aliphatic monocarboxylic acids is obtained from (PMC MDCAT 2022)

  1. fats and oils
  2. proteins and oils
  3. fats and proteins
  4. fats only
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Correct answer: (a) fats and oils

Hydrolysing a fat or an oil gives glycerol and the straight chain fatty acids.

15.Carboxylic acids are water soluble because they: (NUMS MDCAT 2022)

  1. Are more reactive
  2. Have hydrogen bonding
  3. Have low melting point
  4. Have high density
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Correct answer: (b) Have hydrogen bonding

The carboxyl group hydrogen bonds to water, so the lower members dissolve freely.

16.Which of the following is most soluble in water? (PMC Practice 2021)

  1. Ethanoic acid
  2. Pentanoic acid
  3. Hexanoic acid
  4. Butanoic acid
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Correct answer: (a) Ethanoic acid

The shorter the chain the more the carboxyl group tells, so the smallest acid is the most soluble.

17.Which of the following is an example of aromatic carboxylic acid? (PMC Practice 2021)

  1. Ethanoic acid
  2. Butanoic acid
  3. Adipic acid
  4. Phthalic acid
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Correct answer: (d) Phthalic acid

Phthalic acid carries its two carboxyl groups on a benzene ring.

18.In the case of HOCH2CH2CH2COOH, from where is numbering started? (PMC Practice 2021)

  1. OH group is given number 1 position
  2. Carboxylic acid is given number 1 position
  3. COOH is given number 3 position
  4. COOH is given number 4 position
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Correct answer: (b) Carboxylic acid is given number 1 position

The carboxyl carbon is always carbon one.

19.Acetic acid is soluble in? (PMC Practice 2021)

  1. Water, Alcohol, Ether
  2. HCl, HBr, HI
  3. Bromine water
  4. All of these options are correct
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Correct answer: (a) Water, Alcohol, Ether

The carboxyl group hydrogen bonds to water and the alkyl group dissolves in the organic solvents.

20.Nitriles (RCN), on hydrolysis, in the presence of a mineral acid yield: (UHS MDCAT 2019)

  1. Ethers
  2. Carboxylic acids
  3. Aldehydes
  4. Alcohols
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Correct answer: (b) Carboxylic acids

A nitrile hydrolyses to the carboxylic acid and ammonia.

21.The dilute solution of ______ is called vinegar. (UHS MDCAT 2018)

  1. Formic acid
  2. Oxalic acid
  3. Benzoic acid
  4. Acetic acid
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Correct answer: (d) Acetic acid

Vinegar is dilute acetic, that is ethanoic, acid.

22.Final product of hydrolysis of nitrile yield: (UHS MDCAT 2017)

  1. Ketone
  2. Ketone
  3. Alcohol
  4. Carboxylic acid
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Correct answer: (d) Carboxylic acid

A nitrile hydrolyses to the carboxylic acid.

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