ECAT — Engineering College Admission Test (UET)

ECAT Chemistry — Organic Chemistry: Hydrocarbons to Carbonyls (Set 4)

Take the ECAT Chemistry — Organic Chemistry: Hydrocarbons to Carbonyls (Set 4): 30 multiple-choice questions (40 minutes) with instant scoring and a full…

What this test covers

30 ECAT Chemistry

Sample questions with answers

The first 5 questions of this test, with the correct answer and explanation.

Q1. How many structural isomers of the alcohol type (C₅H₁₁OH) exist for the molecular formula C₅H₁₂O?
- A. 10
- B. 4
- C. 8 ✓
- D. 6
Answer: C. 8
Explanation: Pentyl skeleton: 3 pentanols (1-, 2-, 3-). 2-methylbutane skeleton: 4 alcohols (2-methylbutan-1-ol, 3-methylbutan-1-ol, 2-methylbutan-2-ol, 3-methylbutan-2-ol). Neopentane skeleton: 1 (2,2-dimethylpropan-1-ol). Total 8.
Q2. How many stereoisomers does 2,3-dibromobutane, CH₃CHBrCHBrCH₃, have?
- A. 1
- B. 2
- C. 3 ✓
- D. 4
Answer: C. 3
Explanation: It has two stereocentres, but they are identical, so the (2R,3S) form is a meso compound. Stereoisomers: (2R,3R), (2S,3S) and meso = 3 (not 4).
Q3. What is the IUPAC name of CH₃CH=C(CH₃)CH₂CH₃?
- A. 3-Methylpent-2-ene ✓
- B. 2-Methylpent-2-ene
- C. 3-Methylpent-3-ene
- D. 2-Ethylbut-2-ene
Answer: A. 3-Methylpent-2-ene
Explanation: The longest chain containing the double bond has 5 carbons. Numbering from the end nearest the double bond gives C=C at C2 and the methyl at C3: 3-methylpent-2-ene.
Q4. 20 mL of a mixture of methane and ethane is burned and gives 30 mL of CO₂ (same conditions). What volume of O₂ is consumed?
- A. 40 mL
- B. 70 mL
- C. 55 mL ✓
- D. 35 mL
Answer: C. 55 mL
Explanation: Let CH₄ = x and C₂H₆ = y mL: x + y = 20 and x + 2y = 30, so y = 10 and x = 10. O₂ needed: CH₄ needs 2 volumes each (20 mL) and C₂H₆ needs 3.5 each (35 mL). Total = 55 mL.
Q5. In free-radical monochlorination of 2-methylpropane, each tertiary hydrogen is 5 times as reactive as each primary hydrogen. What percentage of the product is 2-chloro-2-methylpropane?
- A. About 50%
- B. About 36% ✓
- C. About 83%
- D. About 10%
Answer: B. About 36%
Explanation: There are 9 primary H (reactivity 1 each = 9) and 1 tertiary H (reactivity 5). Tertiary product = 5/(9 + 5) = 36%.

The other 25 questions

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Q6. A mixture of bromoethane and 2-bromopropane is treated with sodium metal in dry ether (Wurtz reaction). How many different alkanes can form?
- A. 2
- B. 4
- C. 1
- D. 3
Q7. Which alkene is the major product of heating 2-bromobutane with alcoholic KOH?
- A. But-2-ene
- B. But-1-ene
- C. 2-Methylpropene
- D. Butane
Q8. An alkene C₅H₁₀ on ozonolysis (followed by Zn/H₂O) gives only acetone and acetaldehyde. The alkene is
- A. Pent-2-ene
- B. 3-Methylbut-1-ene
- C. 2-Methylbut-2-ene
- D. 2-Methylbut-1-ene
Q9. In the presence of an organic peroxide, HBr adds to propene to give mainly
- A. 1,2-Dibromopropane
- B. 2-Bromopropane
- C. 1-Bromopropane
- D. Propan-1-ol
Q10. Which alkyne gives an aldehyde, not a ketone, on hydration with dilute H₂SO₄ and HgSO₄?
- A. But-2-yne
- B. Propyne
- C. But-1-yne
- D. Ethyne
Q11. Which of the following is aromatic?
- A. Cyclobutadiene
- B. Cyclooctatetraene
- C. Cyclopentadienyl cation, C₅H₅⁺
- D. Cyclopentadienyl anion, C₅H₅⁻
Q12. Which pair correctly gives the main products of chlorinating toluene with (i) Cl₂/light and (ii) Cl₂/FeCl₃?
- A. (i) benzyl chloride; (ii) m-chlorotoluene
- B. (i) o- and p-chlorotoluene; (ii) benzyl chloride
- C. (i) benzyl chloride; (ii) o- and p-chlorotoluene
- D. (i) m-chlorotoluene; (ii) benzyl chloride
Q13. Benzene is treated with 1-chloropropane and anhydrous AlCl₃. The main product is
- A. propylbenzene
- B. isopropylbenzene (cumene)
- C. 1,3-dipropylbenzene
- D. chlorobenzene
Q14. Among phenol, p-nitrophenol, p-cresol and 2,4-dinitrophenol, which is the weakest acid?
- A. p-Nitrophenol
- B. Phenol
- C. 2,4-Dinitrophenol
- D. p-Cresol
Q15. In the Lucas test (anhydrous ZnCl₂ in conc. HCl at room temperature), which alcohol gives turbidity immediately?
- A. Propan-2-ol
- B. Propan-1-ol
- C. Ethanol
- D. 2-Methylpropan-2-ol
Q16. Ethyl tert-butyl ether is best made by the Williamson synthesis using
- A. sodium tert-butoxide and chloroethane
- B. sodium ethoxide and tert-butanol
- C. tert-butanol and ethanol with conc. H₂SO₄ at 140 °C
- D. sodium ethoxide and 2-chloro-2-methylpropane
Q17. Which is the correct order of reactivity towards nucleophilic addition of HCN?
- A. HCHO > CH₃CHO > CH₃COCH₃ > C₆H₅COCH₃
- B. CH₃CHO > HCHO > CH₃COCH₃ > C₆H₅COCH₃
- C. C₆H₅COCH₃ > CH₃COCH₃ > CH₃CHO > HCHO
- D. CH₃COCH₃ > CH₃CHO > HCHO > C₆H₅COCH₃
Q18. Which compound reduces Tollens' reagent but does not reduce Fehling's solution?
- A. Propanone
- B. Benzaldehyde
- C. Glucose
- D. Ethanal
Q19. Ethyl 4-oxopentanoate, CH₃COCH₂CH₂COOC₂H₅, is treated with NaBH₄ in ethanol. Which group is reduced?
- A. Both groups, giving a diol after full reduction
- B. Only the ester group, giving a primary alcohol
- C. Only the ketone group, giving a secondary alcohol
- D. Neither group, because NaBH₄ cannot reduce C=O
Q20. What is the product of the Wolff–Kishner reduction (N₂H₄, KOH, heat) of acetophenone, C₆H₅COCH₃?
- A. Ethylbenzene
- B. Benzoic acid
- C. Styrene
- D. 1-Phenylethanol
Q21. Which Grignard reagent and carbonyl compound, followed by acid hydrolysis, give propan-1-ol?
- A. CH₃MgBr and ethanal
- B. CH₃MgBr and methanal
- C. C₂H₅MgBr and methanal
- D. C₂H₅MgBr and ethanal
Q22. Which of these carbonyl compounds will NOT undergo aldol condensation?
- A. 2,2-Dimethylpropanal, (CH₃)₃CCHO
- B. Propanone
- C. Propanal
- D. Ethanal
Q23. In the crossed Cannizzaro reaction between methanal and benzaldehyde with conc. NaOH, the products are
- A. benzyl alcohol and sodium benzoate
- B. methanol and sodium benzoate
- C. sodium methanoate and benzyl alcohol
- D. methanol and benzyl alcohol
Q24. 78 g of benzene is nitrated with a mixture of conc. HNO₃ and conc. H₂SO₄ to give nitrobenzene (C₆H₅NO₂, M = 123) in 80% yield. What mass of nitrobenzene is obtained? (C = 12, H = 1)
- A. 78 g
- B. 61.5 g
- C. 98.4 g
- D. 123 g
Q25. What volume of ethyne at STP is formed when 12.8 g of calcium carbide (CaC₂, M = 64) reacts with excess water? (CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂)
- A. 22.4 L
- B. 2.24 L
- C. 8.96 L
- D. 4.48 L
Q26. What mass of 2,4,6-tribromophenol (M = 331) is obtained when 9.4 g of phenol (M = 94) reacts completely with excess bromine water?
- A. 9.4 g
- B. 16.6 g
- C. 99.3 g
- D. 33.1 g
Q27. The enthalpy of hydrogenation of cyclohexene is −120 kJ mol⁻¹ and that of benzene to cyclohexane is −208 kJ mol⁻¹. What is the resonance energy of benzene?
- A. 152 kJ mol⁻¹
- B. 28 kJ mol⁻¹
- C. 88 kJ mol⁻¹
- D. 360 kJ mol⁻¹
Q28. (R)-2-Bromobutane reacts with aqueous NaOH by a pure SN2 mechanism. What is the product?
- A. But-2-ene
- B. (S)-Butan-2-ol
- C. (R)-Butan-2-ol
- D. A racemic mixture of butan-2-ol
Q29. How many hyperconjugative structures can be drawn for the tert-butyl cation, (CH₃)₃C⁺?
- A. 1
- B. 3
- C. 9
- D. 6
Q30. Which conformation of n-butane (viewed along the C2–C3 bond) is the most stable?
- A. Gauche (staggered, CH₃ groups 60° apart)
- B. Eclipsed with CH₃ groups 120° apart
- C. Fully eclipsed (CH₃ groups 0° apart)
- D. Anti (staggered, CH₃ groups 180° apart)