Concept:Qualitative chemical tests rely on distinct visual changes corresponding to specific functional group reactivities.
Formula:$$ \text{R-OH} + \text{HCl} \xrightarrow{\text{ZnCl}_2} \text{R-Cl} + \text{H}_2\text{O} $$
Solution:- The Lucas test exploits the varying stabilities of carbocations generated from different classes of alcohols.
- Tertiary alcohols form stable carbocations instantly, generating a cloudy alkyl chloride layer immediately.
- Secondary alcohols take 5-10 minutes, and primary alcohols require heat.
- Thus, it is exclusively a test for identifying and classifying alcohols.
Why other options are incorrect:Alkyl halides are the
products of this test, not the reactants being identified. Alkenes use bromine water or Baeyer's reagent. Carboxylic acids are identified by sodium bicarbonate effervescence.
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.