JEE Main - Carboxylic acids acidity and factors affecting acidic strength Question Bank with Options

1. The acidity of carboxylic acids is a consequence of:

A) The high polarity of the C=O bond.

B) The ease of proton removal and stability of the resulting carboxylate anion.

C) The ability to form strong intermolecular hydrogen bonds.

D) The presence of alpha-hydrogens.

2. Which of the following is a factor that increases the acidity of a carboxylic acid?

A) Electron-donating resonance effect of a substituent on the phenyl ring.

B) Electron-donating inductive effect of an alkyl chain.

C) Electron-withdrawing inductive effect of a halogen atom.

D) Increased steric hindrance around the carboxyl group.

3. Consider the acidity of formic acid, acetic acid, and propanoic acid. The order of decreasing acidity is:

A) Formic acid > Acetic acid > Propanoic acid

B) Propanoic acid > Acetic acid > Formic acid

C) Acetic acid > Formic acid > Propanoic acid

D) Formic acid > Propanoic acid > Acetic acid

4. What is the effect of a strong electron-withdrawing group like a trifluoromethyl (-CF3) group on the acidity of benzoic acid when placed in the meta position?

A) It decreases acidity through resonance donation.

B) It increases acidity through inductive withdrawal.

C) It has no significant effect.

D) It makes the compound a stronger base.

5. The acidity of carboxylic acids is higher than that of alcohols because:

A) The O-H bond in carboxylic acids is more polar.

B) The carboxylate anion is resonance stabilized, while the alkoxide ion is not.

C) Carboxylic acids can form stronger hydrogen bonds.

D) The carbon atom of the carboxyl group is more electronegative than that in an alcohol.

6. Which factor is LEAST likely to increase the acidity of a carboxylic acid?

A) Presence of a halogen atom on the alpha-carbon.

B) Presence of a nitro group on the para position of benzoic acid.

C) Presence of an electron-donating alkyl group.

D) Increased resonance stabilization of the carboxylate anion.

7. Consider the acidity of malonic acid (HOOC-CH2-COOH) and succinic acid (HOOC-CH2-CH2-COOH). Malonic acid is more acidic overall. Why?

A) The two carboxyl groups in malonic acid are electron-donating.

B) The methylene group in malonic acid is electron-withdrawing.

C) The two carboxyl groups in malonic acid exert a stronger electron-withdrawing effect on each other.

D) Succinic acid has a more stable conjugate base.

8. How does the inductive effect of an alkyl group compare to that of a hydrogen atom in terms of acidity?

A) Alkyl groups are electron-donating, decreasing acidity.

B) Alkyl groups are electron-withdrawing, increasing acidity.

C) Alkyl groups have no effect.

D) Alkyl groups increase acidity more than hydrogen.

9. The acidity of a carboxylic acid is directly proportional to:

A) The basicity of the conjugate base.

B) The stability of the conjugate base.

C) The electron-donating ability of substituents.

D) The steric hindrance around the carboxyl group.

10. What is the effect of intramolecular hydrogen bonding in certain substituted carboxylic acids (e.g., ortho-substituted benzoic acids) on their acidity?

A) It increases acidity by stabilizing the acid molecule.

B) It decreases acidity by stabilizing the acid molecule and hindering solvation of the anion.

C) It has no effect on acidity.

D) It increases acidity by making the O-H bond weaker.

11. Which of the following carboxylic acids would be the weakest acid?

A) Salicylic acid

B) Benzoic acid

C) p-Nitrobenzoic acid

D) p-Methoxybenzoic acid

12. Consider the acidity of formic acid and methyl formate. Formic acid is acidic, while methyl formate is essentially neutral. Why?

A) Methyl formate has a more stable carboxylate anion.

B) The O-H bond in formic acid is more polar.

C) The ester linkage in methyl formate does not allow for facile deprotonation.

D) The methyl group is electron-donating, decreasing acidity.

13. What is the effect of introducing a second electron-withdrawing group on the alpha-carbon of a carboxylic acid that already has one?

A) Acidity decreases.

B) Acidity increases further.

C) Acidity remains the same.

D) Acidity becomes negligible.

14. The acidity of a carboxylic acid is influenced by the solvent. Which type of solvent would generally enhance the acidity of carboxylic acids?

A) Non-polar aprotic solvents

B) Polar protic solvents

C) Apolar solvents

D) Hydrophobic solvents

15. Which statement is FALSE regarding the acidity of carboxylic acids?

A) Electron-withdrawing groups increase acidity.

B) Electron-donating groups increase acidity.

C) Acidity is related to the stability of the conjugate base.

D) Formic acid is more acidic than acetic acid.

16. Consider the effect of a sulfonyl group (-SO3H) attached to a benzene ring in the para position to the carboxyl group. How would this affect the acidity of benzoic acid?

A) It would decrease acidity due to electron donation.

B) It would increase acidity due to strong electron withdrawal.

C) It would have no effect.

D) It would make the compound a stronger base.

17. How does the presence of a double bond in the alpha, beta, or gamma position to the carboxyl group affect acidity?

A) It generally decreases acidity due to electron donation.

B) It generally increases acidity due to resonance stabilization of the carboxylate anion.

C) It has no significant effect.

D) It increases acidity only if conjugated with a phenyl ring.

18. Which of the following is the correct order of acidity for formic acid, benzoic acid, and phenol?

A) Phenol > Benzoic acid > Formic acid

B) Formic acid > Benzoic acid > Phenol

C) Benzoic acid > Formic acid > Phenol

D) Formic acid > Phenol > Benzoic acid

19. Consider the effect of a phenyl group attached to the carboxyl carbon (benzoic acid). How does it influence acidity compared to an alkyl group?

A) The phenyl group is electron-donating, decreasing acidity.

B) The phenyl group is electron-withdrawing through resonance, increasing acidity.

C) The phenyl group provides steric hindrance, increasing acidity.

D) The phenyl group has no significant effect.

20. The acidity of a carboxylic acid is directly related to:

A) The basicity of its conjugate base.

B) The stability of its conjugate base.

C) The polarity of the C-H bond.

D) The electronegativity of the alkyl group.

21. Which of the following is an example of a carboxylic acid with a strong electron-withdrawing group that significantly enhances its acidity?

A) Butanoic acid

B) Pentanoic acid

C) 2-Chlorobutanoic acid

D) Hexanoic acid

22. What is the trend in acidity for formic acid, acetic acid, and propanoic acid?

A) Formic acid > Acetic acid > Propanoic acid

B) Propanoic acid > Acetic acid > Formic acid

C) Acetic acid > Formic acid > Propanoic acid

D) Formic acid > Propanoic acid > Acetic acid

23. In oxalic acid (HOOC-COOH), the second dissociation (pKa2) is weaker than the first (pKa1). Why?

A) The carboxylate anion formed after the first dissociation is electron-donating.

B) The two negative charges in the dianion repel each other.

C) The two carboxyl groups are electron-withdrawing.

D) The molecule becomes more polar after the first dissociation.

24. Which statement about the acidity of dicarboxylic acids is generally true?

A) The first dissociation is always stronger than the second.

B) The second dissociation is always stronger than the first.

C) Both dissociations have similar strengths.

D) Acidity is independent of the number of carboxyl groups.

25. The acidity of trifluoroacetic acid (CF3COOH) is significantly higher than that of acetic acid (CH3COOH). This is primarily due to:

A) The high electronegativity and electron-withdrawing inductive effect of the three fluorine atoms.

B) The resonance stabilization provided by the CF3 group.

C) The steric hindrance caused by the CF3 group.

D) The increased polarity of the C-F bonds.

26. Which factor would make a carboxylic acid *less* acidic?

A) A nitro group in the para position of benzoic acid.

B) An amino group in the para position of benzoic acid.

C) A halogen atom in the ortho position of benzoic acid.

D) A methoxy group in the ortho position of benzoic acid.

27. What is the role of the carbonyl oxygen in the acidity of carboxylic acids?

A) It withdraws electron density from the hydroxyl group, making the O-H bond more polar.

B) It donates electron density to the hydroxyl group, weakening the O-H bond.

C) It stabilizes the hydrogen atom, making it easier to remove.

D) It participates in hydrogen bonding, increasing acidity.

28. Consider a carboxylic acid with a strong electron-withdrawing group like -CN in the beta-position. How would this affect its acidity compared to a similar acid without the -CN group?

A) Acidity would decrease significantly.

B) Acidity would increase slightly.

C) Acidity would increase significantly.

D) Acidity would remain unchanged.

29. Which of the following is a correct statement about the acidity of carboxylic acids?

A) Acidity increases with electron-donating groups.

B) Acidity decreases with electron-withdrawing groups.

C) Acidity is primarily due to the stability of the carboxylate anion.

D) Acidity is independent of resonance effects.

30. How does the hybridization of the carbon atom attached to the carboxyl group affect acidity?

A) sp3 hybridization increases acidity.

B) sp2 hybridization increases acidity.

C) sp hybridization increases acidity.

D) Hybridization has no effect on acidity.

31. What is the primary reason for the difference in acidity between carboxylic acids and alcohols?

A) The C-O bond in alcohols is stronger than the C-O bond in carboxylic acids.

B) The conjugate base of an alcohol (alkoxide) is less stable than the carboxylate anion.

C) The O-H bond in alcohols is less polar than in carboxylic acids.

D) Alcohols can undergo hydrogen bonding more effectively.

32. Why is formic acid considered a stronger acid than acetic acid?

A) The O-H bond in formic acid is more polar.

B) The formate anion is less resonance stabilized than the acetate anion.

C) The methyl group in acetic acid is electron-donating, destabilizing the acetate anion.

D) The hydrogen atom in formic acid is electron-withdrawing.

33. Consider the acidity of substituted benzoic acids. Electron-donating groups on the phenyl ring will:

A) Increase acidity.

B) Decrease acidity.

C) Have no effect on acidity.

D) Make the compound a stronger base.

34. What is the effect of a fluorine atom on the acidity of a carboxylic acid compared to a chlorine atom at the same position?

A) Fluorine increases acidity more than chlorine.

B) Chlorine increases acidity more than fluorine.

C) They have the same effect.

D) Both decrease acidity.

35. The pKa of an acid is a measure of its acidity. A lower pKa indicates:

A) A stronger acid.

B) A weaker acid.

C) A neutral compound.

D) An equilibrium mixture.

36. Which of the following substituents would most significantly increase the acidity of a carboxylic acid?

A) Methyl (-CH3)

B) Methoxy (-OCH3)

C) Nitro (-NO2)

D) Ethyl (-CH2CH3)

37. How does resonance within the carboxylic acid molecule itself influence its acidity?

A) It stabilizes the acid, making it less acidic.

B) It destabilizes the acid, making it more acidic.

C) It has no effect on the acidity.

D) It increases the polarity of the O-H bond, increasing acidity.

38. What is the relative acidity order of formic acid, acetic acid, and trichloroacetic acid?

A) Formic acid > Acetic acid > Trichloroacetic acid

B) Trichloroacetic acid > Formic acid > Acetic acid

C) Trichloroacetic acid > Acetic acid > Formic acid

D) Acetic acid > Formic acid > Trichloroacetic acid

39. Consider the acidity of benzoic acid and cyclohexanecarboxylic acid. Benzoic acid is more acidic. Why?

A) The phenyl ring is electron-donating.

B) The carboxylate anion of benzoic acid is more resonance stabilized by the phenyl ring.

C) The carboxylate anion of cyclohexanecarboxylic acid is destabilized by the saturated ring.

D) Cyclohexane is a more polar ring than benzene.

40. What is the effect of increasing the distance of an electron-withdrawing group from the carboxyl group on acidity?

A) Acidity increases as the distance increases.

B) Acidity decreases as the distance increases.

C) Acidity remains unchanged.

D) Acidity increases only if the group is within two carbons.

41. Why are phenols generally more acidic than aliphatic alcohols but less acidic than carboxylic acids?

A) Phenols are stabilized by resonance, but less than carboxylate anions.

B) Alcohols are stabilized by inductive effect, but less than phenols.

C) Carboxylate anions are less stable than phenoxide ions.

D) Alcohols form more stable conjugate bases than phenols or carboxylate anions.

42. The acidity of carboxylic acids is generally compared to which other class of organic compounds?

A) Alcohols

B) Phenols

C) Amines

D) Ethers

43. Which of the following carboxylic acids is expected to be the strongest acid?

A) Propanoic acid

B) Ethanoic acid

C) Chloroacetic acid

D) Dichloroacetic acid

44. How does the number of electron-withdrawing groups attached to the alpha-carbon affect the acidity of a carboxylic acid?

A) Increases acidity with each additional group.

B) Decreases acidity with each additional group.

C) No significant change in acidity.

D) Increases acidity only if the groups are halogens.

45. What is the approximate pKa value of a typical aliphatic carboxylic acid like acetic acid?

A) 1-2

B) 3-4

C) 4-5

D) 7-8

46. Consider formic acid (HCOOH) and acetic acid (CH3COOH). Which is more acidic and why?

A) Acetic acid is more acidic due to the electron-withdrawing effect of the methyl group.

B) Formic acid is more acidic because the hydrogen atom is less electron-donating than the methyl group.

C) Formic acid is more acidic because the carboxylate anion is more resonance stabilized.

D) Acetic acid is more acidic due to steric hindrance in formic acid.

47. Which factor generally leads to an increase in the acidity of carboxylic acids?

A) Presence of electron-donating groups.

B) Presence of electron-withdrawing groups.

C) Longer alkyl chains.

D) Steric hindrance around the carboxyl group.

48. How does the electron-withdrawing inductive effect of a substituent on the alkyl chain affect the acidity of a carboxylic acid?

A) It decreases acidity by destabilizing the carboxylate anion.

B) It increases acidity by stabilizing the carboxylate anion.

C) It has no significant effect on the acidity.

D) It increases acidity by destabilizing the carboxylate anion.

49. Which of the following statements best describes the stability of the carboxylate anion?

A) The negative charge is localized on the oxygen atom.

B) The negative charge is delocalized between the two oxygen atoms through resonance.

C) The negative charge is stabilized by the adjacent alkyl group.

D) The negative charge is destabilized by the carbonyl oxygen.

50. What is the primary reason for the acidic nature of carboxylic acids?

A) The presence of the carbonyl group (C=O).

B) The ability to form a stable carboxylate anion upon deprotonation.

C) The inductive effect of alkyl groups attached to the carboxyl group.

D) The resonance stabilization of the carboxylic acid molecule itself.

Carboxylic acids acidity and factors affecting acidic strength - Question Bank