Concept:The acidic strength of a compound depends directly on the stability of its conjugate base.
Formula:$$ \text{HA} \rightleftharpoons \text{H}^+ + \text{A}^- $$
Solution:- Carboxylic acids form highly stable carboxylate ions due to resonance across two electronegative oxygen atoms (Strongest).
- Phenols form phenoxide ions stabilized by resonance in the benzene ring, but less stable than carboxylate.
- Water forms hydroxide (\(\text{OH}^-\)), which is stable but lacks resonance stabilization.
- Alcohols form alkoxide ions where the alkyl group exhibits an electron-donating (+I) effect, intensifying the negative charge and making it the least stable conjugate base (Weakest acid).
Why other options are incorrect:Only Option B correctly orders the resonance stability and +I effects governing the respective conjugate bases.
Quality & Fidelity Assurance:
Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.