MDCAT Chemistry chapter 18: Chemistry · Carboxylic acids MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

51 exam-style questions on Chemistry · Carboxylic acids, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

51 questions · 1 topics · 10 per test

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What chapter 18 covers

Ten Chemistry · Carboxylic acids questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. Sodium benzoate, C6H5COONa, is heated strongly with soda lime. The organic product is

  1. A
    benzene
  2. B
    methylbenzene
  3. C
    phenol
  4. D
    benzaldehyde
Show answer

Answer: A. Decarboxylation removes the –COONa group as Na2CO3 and puts H in its place: C6H5COONa + NaOH → C6H6 + Na2CO3. Methylbenzene would keep all seven carbons, which needs reduction, not decarboxylation.

2. The IUPAC name of (CH3)2CHCOOH is

  1. A
    2-methylpropanoic acid
  2. B
    2-methylbutanoic acid
  3. C
    1-methylpropanoic acid
  4. D
    3-methylpropanoic acid
Show answer

Answer: A. Numbering starts at the COOH carbon (C-1), so the CH carrying the methyl branch is C-2 of a three-carbon chain. 2-Methylbutanoic acid would contain five carbons, not four.

3. Methane can be prepared in the laboratory by heating

  1. A
    sodium propanoate with soda lime
  2. B
    sodium methanoate with soda lime
  3. C
    ethanoic acid with HI and red phosphorus
  4. D
    sodium ethanoate with soda lime
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Answer: D. Soda lime (NaOH with CaO) removes the carboxyl carbon as Na2CO3: CH3COONa + NaOH → CH4 + Na2CO3, so the alkane has one carbon fewer than the salt. Sodium propanoate gives ethane, and HI with red phosphorus keeps every carbon, turning ethanoic acid into ethane.

4. Apart from water, which species is present in the greatest amount in 0.10 mol dm−3 aqueous ethanoic acid?

  1. A
    CH3COO− ions, as the acid ionises almost completely
  2. B
    CH3COOH molecules, as only a small fraction ionises
  3. C
    H3O+ ions, as each molecule releases several protons
  4. D
    OH− ions, as ethanoate ions react with water
Show answer

Answer: B. Ethanoic acid is a weak acid: CH3COOH + H2O ⇌ CH3COO− + H3O+ lies far to the left, with only about 1% of the molecules ionised, whereas a mineral acid such as HCl is fully ionised. Only the –COOH hydrogen is acidic, so each molecule can give at most one proton.

5. Which order shows decreasing reactivity of acid derivatives towards nucleophiles?

  1. A
    amide > ester > acid anhydride > acid chloride
  2. B
    acid chloride > acid anhydride > ester > amide
  3. C
    acid anhydride > acid chloride > amide > ester
  4. D
    ester > acid chloride > amide > acid anhydride
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Answer: B. Cl− is the best leaving group and chlorine withdraws electrons strongly, so acid chlorides react fastest. In amides the nitrogen lone pair feeds electrons to the C=O carbon, making them the least reactive.

6. Ethanenitrile, CH3CN, is boiled with aqueous sodium hydroxide until hydrolysis is complete. The products are

  1. A
    sodium ethanoate and ammonia
  2. B
    ethanamide and sodium cyanide
  3. C
    ethanoic acid and ammonia
  4. D
    ethanoic acid and ammonium chloride
Show answer

Answer: A. The nitrile is hydrolysed via ethanamide, CH3CONH2; in alkali the nitrogen leaves as ammonia gas and the acid stays as its salt: CH3CN + NaOH + H2O → CH3COONa + NH3. With dilute hydrochloric acid instead, the products are ethanoic acid and ammonium chloride.

7. N-Ethylethanamide, CH3CONHCH2CH3, can be made at room temperature by reacting ethanoyl chloride with

  1. A
    ethanol, CH3CH2OH
  2. B
    ammonia, NH3
  3. C
    chloroethane, CH3CH2Cl
  4. D
    ethylamine, CH3CH2NH2
Show answer

Answer: D. An acyl chloride reacts with a primary amine to give an N-substituted amide: CH3COCl + 2CH3CH2NH2 → CH3CONHCH2CH3 + CH3CH2NH3+Cl−. Ethanol would give the ester ethyl ethanoate, and ammonia the unsubstituted amide ethanamide.

8. In the common system, CH3COCH2COOH is called β-ketobutyric acid. Its IUPAC name is

  1. A
    3-oxobutanoic acid
  2. B
    2-oxobutanoic acid
  3. C
    3-oxobutanal
  4. D
    2-oxopropanoic acid
Show answer

Answer: A. Greek letters start at the carbon next to –COOH (α = C-2), so β is C-3, and a ketone C=O in a chain ending in –COOH is shown by the prefix oxo-. Taking β as C-2 gives 2-oxobutanoic acid, a different compound.

9. Two acids have Ka values of 1.0 × 10−4 and 1.0 × 10−5 mol dm−3. Compared with the second acid, the first acid

  1. A
    is weaker, and its pKa is higher by 1
  2. B
    is stronger, and its pKa is higher by 1
  3. C
    is weaker, and its pKa is lower by 1
  4. D
    is stronger, and its pKa is lower by 1
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Answer: D. A larger Ka means more ionisation, so the first acid is stronger. pKa = −log Ka gives 4 and 5, so the stronger acid has the lower pKa, by 1 unit for a tenfold difference in Ka.

10. Which common name of a carboxylic acid is correctly matched with its IUPAC name?

  1. A
    formic acid – ethanoic acid
  2. B
    butyric acid – 2-methylpropanoic acid
  3. C
    propionic acid – propanoic acid
  4. D
    acetic acid – methanoic acid
Show answer

Answer: C. Propionic acid, CH3CH2COOH, is propanoic acid. Formic acid (HCOOH) is methanoic acid, acetic acid is ethanoic acid, and butyric acid is straight-chain butanoic acid; 2-methylpropanoic acid is its branched isomer, isobutyric acid.

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How many Chemistry · Carboxylic acids MCQs are there?

51, each with the answer and a short explanation, across 1 topics: Carboxylic acids and derivatives. Every chapter test draws ten of them, so you can take it many times.

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Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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