ECAT — Engineering College Admission Test (UET)
Take the ECAT Chemistry — Organic Chemistry: Hydrocarbons to Carbonyls (Set 6): 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. How many structural isomers of molecular formula C₄H₁₀O are alcohols (not ethers)?
Answer: B. 4
Explanation: Butan-1-ol, butan-2-ol, 2-methylpropan-1-ol and 2-methylpropan-2-ol. (The remaining three C₄H₁₀O isomers are ethers.)
Q2. 20 cm³ of ethyne (C₂H₂) is burned in excess oxygen: 2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O. The volume of oxygen consumed, measured at the same temperature and pressure, is:
Answer: C. 50 cm³
Explanation: 2 volumes of C₂H₂ need 5 volumes of O₂, so 20 cm³ needs 20 × 5/2 = 50 cm³ (and gives 40 cm³ CO₂).
Q3. The major product of the addition of HCl to 2-methylbut-2-ene, (CH₃)₂C=CHCH₃, is:
Answer: D. 2-chloro-2-methylbutane
Explanation: By Markovnikov's rule H adds to the carbon with more hydrogens (CHCH₃) giving the tertiary carbocation (CH₃)₂C⁺CH₂CH₃, which captures Cl⁻. Product: 2-chloro-2-methylbutane (tertiary), a more stable cation than the secondary one that gives 2-chloro-3-methylbutane.
Q4. Reductive ozonolysis of 2-methylbut-2-ene, (CH₃)₂C=CHCH₃, gives:
Answer: B. propanone and ethanal
Explanation: Cleavage of the C=C gives (CH₃)₂C=O (propanone) from one carbon and CH₃CH=O (ethanal) from the other.
Q5. Hydration of but-2-yne, CH₃C≡CCH₃, with dilute H₂SO₄ and HgSO₄ gives:
Answer: D. butan-2-one
Explanation: Addition of water gives an unstable enol, CH₃C(OH)=CHCH₃, that tautomerises to the ketone CH₃COCH₂CH₃, butan-2-one. (Only ethyne gives an aldehyde.)
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Q6. How many of the alkynes of molecular formula C₅H₈ give a white precipitate with ammoniacal silver nitrate?
Q7. Heating 2-bromo-2-methylbutane with alcoholic KOH gives mainly which alkene (the more highly substituted alkene is favoured)?
Q8. In SN2 reactions with a given nucleophile in the same solvent, which of CH₃F, CH₃Cl, CH₃Br and CH₃I reacts fastest?
Q9. In the nitration of benzene with a mixture of concentrated HNO₃ and H₂SO₄, the role of sulphuric acid is to:
Q10. The nitration of chlorobenzene mainly gives 2- and 4-nitrochlorobenzene, and occurs more slowly than the nitration of benzene. This is because chlorine:
Q11. Benzene reacts with chloroethane in the presence of anhydrous AlCl₃. The major product is:
Q12. Toluene is chlorinated under conditions that allow substitution of both ring and side-chain hydrogens by a single chlorine atom. How many different monochloro products of C₇H₇Cl are possible?
Q13. How many moles of hydrogen gas are liberated when 1 mol of glycerol, HOCH₂CH(OH)CH₂OH, reacts completely with excess sodium?
Q14. Which route is the better way to make methyl tert-butyl ether, (CH₃)₃C–O–CH₃, by the Williamson synthesis?
Q15. Which test distinguishes benzoic acid from phenol?
Q16. 0.94 g of phenol (C₆H₅OH = 94 g mol⁻¹) is treated with excess bromine water to give 2,4,6-tribromophenol, C₆H₂Br₃OH (Br = 80). The mass of the white precipitate is:
Q17. Ethanal is oxidised to ethanoate by Tollens' reagent: CH₃CHO + 2[Ag(NH₃)₂]⁺ + 3OH⁻ → CH₃COO⁻ + 2Ag + 4NH₃ + 2H₂O. The mass of silver deposited by 0.10 mol of ethanal (Ag = 108) is:
Q18. Which of these aldehydes undergoes the Cannizzaro reaction with concentrated NaOH?
Q19. Which of the following does NOT give a yellow precipitate of iodoform with I₂ and NaOH?
Q20. The pKa values of ethanoic acid and chloroethanoic acid are 4.76 and 2.87. How many times stronger is chloroethanoic acid (ratio of Ka values)?
Q21. 1.0 mol of ethanoic acid and 1.0 mol of ethanol are mixed with a little acid catalyst, and the equilibrium constant for esterification is K_c = 4.0. The moles of ethyl ethanoate at equilibrium are:
Q22. 8.8 g of ethyl ethanoate (C₄H₈O₂ = 88 g mol⁻¹) is hydrolysed completely with aqueous NaOH to give sodium ethanoate (CH₃COONa = 82 g mol⁻¹) and ethanol. The mass of sodium ethanoate is:
Q23. Arrange ethylamine, ammonia and aniline in order of increasing basic strength in water.
Q24. The number of stereoisomers (including the meso form) of butane-2,3-diol, CH₃CH(OH)CH(OH)CH₃, is:
Q25. The number of geometrical isomers of hexa-2,4-diene, CH₃–CH=CH–CH=CH–CH₃, is:
Q26. Propane is reacted with chlorine in sunlight until dichlorides are formed. How many different dichloropropane structural isomers are possible?
Q27. A mixture of iodomethane and iodoethane is treated with sodium metal in dry ether (Wurtz reaction). How many different alkanes can form?
Q28. Thermal cracking of decane, C₁₀H₂₂, gives pentane (C₅H₁₂) as one product. The other product is:
Q29. Benzene is treated with bromine in the presence of iron(III) bromide. Which statement about the reaction is correct?
Q30. Ethylmagnesium bromide, C₂H₅MgBr, reacts with propanone and the product is hydrolysed with dilute acid. The product is: