ECAT — Engineering College Admission Test (UET)

ECAT Chemistry — Organic Chemistry: Hydrocarbons to Carbonyls (Set 1)

Take the ECAT Chemistry — Organic Chemistry: Hydrocarbons to Carbonyls (Set 1): 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. The IUPAC name of CH₃–CH(CH₃)–CH₂–CH₃ is:
- A. 1,1-dimethylpropane
- B. 2-methylbutane ✓
- C. 2-ethylpropane
- D. 3-methylbutane
Answer: B. 2-methylbutane
Explanation: The longest chain has 4 carbons and the methyl group gets the lowest locant, 2.
Q2. How many structural isomers does pentane (C₅H₁₂) have?
- A. 3 ✓
- B. 4
- C. 5
- D. 2
Answer: A. 3
Explanation: n-pentane, 2-methylbutane and 2,2-dimethylpropane.
Q3. Which alcohol is optically active?
- A. 2-methylpropan-2-ol
- B. butan-1-ol
- C. propan-2-ol
- D. butan-2-ol ✓
Answer: D. butan-2-ol
Explanation: In butan-2-ol, C-2 carries four different groups (H, OH, CH₃, C₂H₅), so it is chiral; the others have no such carbon.
Q4. The initiation step in the chlorination of methane in sunlight is:
- A. Cl• + Cl• → Cl₂
- B. Cl₂ → 2Cl• ✓
- C. CH₃• + Cl₂ → CH₃Cl + Cl•
- D. CH₄ → CH₃⁺ + H⁻
Answer: B. Cl₂ → 2Cl•
Explanation: UV light splits Cl₂ homolytically into free radicals, starting the chain reaction; the others are propagation and termination steps.
Q5. Ethene decolourizes cold, dilute alkaline KMnO₄ (Baeyer's reagent) and forms:
- A. ethane-1,2-diol ✓
- B. ethanal
- C. ethanoic acid
- D. ethanol
Answer: A. ethane-1,2-diol
Explanation: The C=C is hydroxylated: CH₂=CH₂ + [O] + H₂O → HOCH₂CH₂OH (ethylene glycol).

The other 25 questions

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Q6. Addition of HBr to propene (no peroxide) gives mainly:
- A. 2-bromopropane
- B. propyl bromide and H₂
- C. 1,2-dibromopropane
- D. 1-bromopropane
Q7. When HBr adds to propene in the presence of a peroxide, the main product is:
- A. 1-bromopropane
- B. 2-bromopropane
- C. propan-2-ol
- D. 2,2-dibromopropane
Q8. Ozonolysis of but-2-ene (CH₃CH=CHCH₃) followed by treatment with Zn/H₂O gives:
- A. two molecules of ethanoic acid only
- B. butanal
- C. two molecules of ethanal
- D. one molecule of propanone and one of methanal
Q9. Which compound gives a white precipitate with ammoniacal AgNO₃ solution?
- A. ethane
- B. ethene
- C. but-2-yne
- D. ethyne
Q10. Ethyne reacts with water in the presence of dilute H₂SO₄ and HgSO₄ to give:
- A. ethanoic acid
- B. propanone
- C. ethanol
- D. ethanal (acetaldehyde)
Q11. In the sulphonation of benzene with fuming sulphuric acid, the attacking electrophile is:
- A. SO₂
- B. SO₃
- C. HSO₄⁻
- D. H₃O⁺
Q12. The catalyst used in the Friedel–Crafts alkylation of benzene is:
- A. Pt
- B. Ni
- C. anhydrous AlCl₃
- D. conc. H₂SO₄
Q13. In electrophilic substitution of nitrobenzene, the incoming group enters mainly at the:
- A. ortho and para positions equally
- B. meta position
- C. para position
- D. ortho position
Q14. Which substituent on benzene is deactivating but directs incoming groups to ortho and para positions?
- A. –OH
- B. –Cl
- C. –CH₃
- D. –NO₂
Q15. Which statement about an SN2 reaction is correct?
- A. It is fastest for tertiary alkyl halides
- B. Its rate depends only on the alkyl halide concentration
- C. It goes through a carbocation intermediate
- D. It takes place in one step with inversion of configuration
Q16. The SN1 reaction of an optically active alkyl halide usually gives:
- A. a mixture of both configurations (racemization)
- B. no substitution product
- C. complete retention of configuration
- D. complete inversion of configuration
Q17. CH₃MgBr reacts with propanone (acetone) and the product is hydrolysed. The final product is:
- A. 2-methylpropan-1-ol
- B. butan-2-ol
- C. 2-methylpropan-2-ol
- D. propan-2-ol
Q18. In the Lucas test (conc. HCl + ZnCl₂), which alcohol produces turbidity immediately?
- A. 2-methylpropan-2-ol
- B. butan-2-ol
- C. methanol
- D. butan-1-ol
Q19. Ethanol is refluxed with excess acidified K₂Cr₂O₇. The main organic product is:
- A. ethoxyethane
- B. ethanoic acid
- C. ethene
- D. ethanal
Q20. Phenol is a stronger acid than ethanol because:
- A. the ethoxide ion is stabilized by resonance
- B. phenol has more hydrogen atoms
- C. phenol forms stronger hydrogen bonds with water
- D. the phenoxide ion is stabilized by resonance with the benzene ring
Q21. Phenol reacts with bromine water at room temperature to give a white precipitate of:
- A. 4-bromophenol only
- B. 2,4,6-tribromophenol
- C. 2-bromophenol only
- D. bromobenzene
Q22. Williamson's synthesis is used to prepare ethers by reacting:
- A. an alkyl halide with a sodium alkoxide
- B. two alcohols with conc. HNO₃
- C. an alkene with water
- D. an aldehyde with an alcohol
Q23. Tollens' reagent (ammoniacal silver nitrate) can be used to distinguish:
- A. primary amines from secondary amines
- B. aldehydes from ketones
- C. alkanes from alkenes
- D. alcohols from ethers
Q24. Which compound does NOT give the iodoform test?
- A. ethanal
- B. propanone
- C. ethanol
- D. propanal
Q25. Which aldehyde undergoes the Cannizzaro reaction with concentrated NaOH?
- A. propanal
- B. methanal (HCHO)
- C. ethanal
- D. butanal
Q26. Aldol condensation is shown by aldehydes that:
- A. have no α-hydrogen atom
- B. contain a benzene ring only
- C. have at least one α-hydrogen atom
- D. have a –COOH group
Q27. Addition of HCN to ethanal gives a cyanohydrin. This is an example of:
- A. nucleophilic addition
- B. elimination
- C. free radical substitution
- D. electrophilic addition
Q28. Carbonyl compounds react with 2,4-dinitrophenylhydrazine (2,4-DNPH) to give:
- A. a silver mirror
- B. a brick-red precipitate of Cu₂O
- C. a yellow-orange precipitate
- D. a purple colour
Q29. An alkane has a molar mass of 72 g mol⁻¹. Its molecular formula is:
- A. C₆H₁₄
- B. C₄H₁₀
- C. C₅H₁₂
- D. C₅H₁₀
Q30. All carbon–carbon bonds in benzene have a length of 1.39 Å. This is because:
- A. all carbons are sp³ hybridized
- B. the π electrons are delocalized over all six sp² carbon atoms
- C. benzene is non-planar
- D. benzene has three isolated single and three isolated double bonds