ECAT — Engineering College Admission Test (UET)
Take the ECAT Chemistry — Organic Chemistry: Hydrocarbons to Carbonyls (Set 2): 30 multiple-choice questions (40 minutes) with instant scoring and a full…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. The IUPAC name of CH₃–CH=C(CH₃)–CH₃ is:
Answer: D. 2-methylbut-2-ene
Explanation: Number the 4-carbon chain from the end nearer the double bond: the C=C starts at C-2 and the methyl group is on C-2.
Q2. How many structural isomers of C₄H₁₀O are alcohols?
Answer: A. 4
Explanation: Butan-1-ol, butan-2-ol, 2-methylpropan-1-ol and 2-methylpropan-2-ol. (The other three C₄H₁₀O isomers are ethers.)
Q3. Cis-but-2-ene and trans-but-2-ene do not interconvert at room temperature because:
Answer: C. Rotation about the C=C bond would require breaking the π bond
Explanation: The π bond is formed by sideways overlap of parallel p orbitals; twisting the molecule would destroy this overlap, which needs about 250 kJ mol⁻¹.
Q4. How many structural isomers are possible for dichlorobenzene, C₆H₄Cl₂?
Answer: A. 3
Explanation: The two Cl atoms can be 1,2 (ortho), 1,3 (meta) or 1,4 (para).
Q5. What volume of oxygen is needed for the complete combustion of 2 dm³ of propane, measured at the same temperature and pressure?
Answer: B. 10 dm³
Explanation: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O; by Gay-Lussac's law 2 dm³ propane needs 2 × 5 = 10 dm³ O₂.
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Q6. A mixture of CH₃Br and C₂H₅Br is treated with sodium in dry ether (Wurtz reaction). The alkanes formed are:
Q7. Heating sodium propanoate (CH₃CH₂COONa) with soda lime gives:
Q8. 2-Bromobutane is heated with alcoholic KOH. According to Saytzeff's rule, the major product is:
Q9. Ethanol heated with excess concentrated H₂SO₄ at about 170°C gives mainly:
Q10. Alkenes are converted to alkanes by hydrogen gas in the presence of finely divided nickel at about 250°C. This is called:
Q11. What mass of bromine adds completely to 14 g of ethene (C₂H₄ + Br₂ → C₂H₄Br₂; Br = 80)?
Q12. Ethyne is prepared in the laboratory by the action of water on:
Q13. Ethyne is more acidic than ethene and ethane because:
Q14. When ethyne is passed through a red-hot iron tube, three molecules combine to give:
Q15. When benzene is treated with chlorine in bright sunlight in the absence of a catalyst, the product is:
Q16. In the nitration of benzene with a mixture of concentrated HNO₃ and H₂SO₄, the electrophile is:
Q17. Toluene is heated with alkaline KMnO₄ and then acidified. The organic product is:
Q18. Chlorine is passed into boiling toluene in sunlight without a catalyst. The main product is:
Q19. The reactivity of alkyl halides towards nucleophilic substitution is in the order R–I > R–Br > R–Cl > R–F because:
Q20. Ethyl bromide reacts with aqueous KOH and with alcoholic KOH. The main products are respectively:
Q21. Which alkyl halide undergoes SN1 reaction most rapidly?
Q22. To prepare propan-1-ol using a Grignard reagent, ethylmagnesium bromide should be treated with ______ followed by acid hydrolysis.
Q23. In the fermentation of glucose to ethanol, the enzyme that converts glucose into ethanol and CO₂ is:
Q24. Phenol dissolves in aqueous NaOH but does not liberate CO₂ from aqueous NaHCO₃. This shows that phenol is:
Q25. Which reagent can be used to distinguish phenol from ethanol?
Q26. An aldehyde, but not a ketone, reduces Fehling's solution on warming to give a red precipitate of:
Q27. Which carbonyl compound is the most reactive towards nucleophilic addition?
Q28. Reduction of propanone with NaBH₄ (or H₂/Ni) gives:
Q29. Ketones are generally prepared in the laboratory by the oxidation of:
Q30. A hydrocarbon of molar mass 42 g mol⁻¹ decolourizes bromine water. Its molecular formula is: