Board-style MCQs and past-paper questions in the BIEK / Sindh Board pattern. Tap an option to check yourself instantly. Solved questions are at the bottom.
Multiple-choice questions
Solved questions & self-assessment (past papers)
Distinguish 1°, 2° and 3° alcohols by the Lucas test
Add Lucas reagent (conc. HCl + anhydrous ZnCl₂) to each.
• Tertiary (3°) → turbidity immediately.
• Secondary (2°) → turbidity in about 5 minutes.
• Primary (1°) → no turbidity at room temperature.
Order of reactivity: 3° > 2° > 1° (most stable carbocation reacts fastest).
How do you distinguish phenol from ethanol?
Add neutral FeCl₃ solution. Phenol gives a violet (purple) colour; ethanol gives no colour.
Alternatively, phenol reacts with NaOH to give sodium phenoxide (it is acidic); ethanol does not.
Give the products of oxidising a 1° and a 2° alcohol with K₂Cr₂O₇
1° alcohol (e.g. ethanol) → aldehyde → carboxylic acid: CH₃CH₂OH → CH₃CHO → CH₃COOH.
2° alcohol (e.g. propan-2-ol) → ketone and stops: (CH₃)₂CHOH → (CH₃)₂C=O.
In both, the orange dichromate turns green (Cr³⁺). A 3° alcohol leaves it orange — no reaction.