Carboxylic acids Knowledge-Based Download PDF

Questions

1. 1.

   Which of the following reagents produces brisk effervescence of carbon dioxide gas when added to an aqueous solution of a carboxylic acid, serving as a classic qualitative test to distinguish it from an alcohol?

   • A) Sodium hydrogen carbonate ($\text{NaHCO}_3$)
   • B) Sodium borohydride ($\text{NaBH}_4$)
   • C) Acidified potassium dichromate ($\text{K}_2\text{Cr}_2\text{O}_7$)
   • D) Bromine water ($\text{Br}_2/\text{H}_2\text{O}$)
2. 2.

   Which class of organic compounds is synthesized when a carboxylic acid reacts with an alcohol in the presence of a strong acid catalyst?

   • A) Ester
   • B) Ether
   • C) Acid anhydride
   • D) Aldehyde
3. 3.

   Carboxylic acids exhibit significantly greater acidity than alcohols of comparable molecular mass. Which of the following is the primary reason for this marked difference in acid strength?

   • A) The electron-donating inductive effect of the carbonyl carbon that stabilizes the un-ionized acid
   • B) The complete dissociation of carboxylic acid molecules into hydronium ions in aqueous solution
   • C) The formation of strong intramolecular hydrogen bonds within the conjugate base
   • D) The resonance stabilization of the carboxylate anion, which delocalizes the negative charge over two electronegative oxygen atoms
4. 4.

   Which of the following statements correctly explains why carboxylic acids exhibit higher boiling points than alcohols of comparable molecular mass?

   • A) They form stable cyclic dimers held together by two intermolecular hydrogen bonds between molecules.
   • B) They contain nonpolar carbonyl groups that eliminate dipole-dipole repulsions in the liquid phase.
   • C) They completely dissociate into free ions that form high-melting extended ionic networks.
   • D) They lack hydroxyl groups, enabling unusually strong London dispersion forces to dominate.
5. 5.

   Which of the following statements correctly describes the functional group and characteristic chemical behavior of carboxylic acids?

   • A) The carboxyl group consists of a carbonyl group and a hydroxyl group bonded to the same carbon atom, enabling the molecule to donate a proton as a weak acid.
   • B) The carboxyl group contains an ether oxygen between two carbonyl carbons, preventing the molecule from participating in intermolecular hydrogen bonding.
   • C) The carboxyl group acts primarily as a Brønsted–Lowry base because the carbonyl oxygen readily accepts protons from neutral water.
   • D) The carboxyl group is formed by the direct linkage of a carbonyl group and an amino group, allowing it to behave as an amphoteric zwitterion.