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120 questions · 120 marks · 2 hours
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Correct answer: (B) Ba(N₃)₂ → Ba + 3N₂
Thermal decomposition of barium azide gives pure nitrogen, since no other gas is formed.
Correct answer: (A) C₂H₆
Electrolysis of potassium acetate—Kolbe's reaction—joins two methyl radicals to give ethane, C₂H₆.
Correct answer: (A) N₂O
Nitrous oxide (N₂O) is used as an anaesthetic and is also called laughing gas.
Correct answer: (A) Butane
Sodium acting on ethyl iodide—Wurtz reaction—joins two ethyl groups to give butane.
Correct answer: (D) More than one of the above
Concentrated nitric acid is reduced to NO₂ with carbon, with sulphur and with copper alike, so the answer is ‘more than one’.
Correct answer: (C) CH≡CH
The carbons of ethyne are sp hybridized, with the greatest s character, so its hydrogen leaves most readily and it is the most acidic.
Correct answer: (B) C₂—C₃
The inductive effect dies away along the chain, so it is least in the C₂—C₃ bond, the one farthest from the bromine.
Correct answer: (C) CH₃CHO
With dilute sulphuric acid and HgSO₄ water adds to ethyne, and the unstable enol rearranges to acetaldehyde, CH₃CHO.
Correct answer: (B) Isomerization
The molecular formula stays the same and only the position of the double bond shifts, so the change is an isomerization.
Correct answer: (C) C₆H₅(H)C=CH—CH₃
Cis-trans isomerism needs two different groups on each carbon of the double bond, and only C₆H₅(H)C=CH—CH₃ meets that condition.
Correct answer: (D) More than one of the above
Both the Fischer–Tropsch process and the Bergius process were developed for making petrol, so the answer is ‘more than one’.
Correct answer: (C) Isoprene
Natural rubber is a polymer of isoprene, that is 2-methyl-1,3-butadiene.
Correct answer: (E) None of the above
By Hückel's rule a ring is aromatic if it holds (4n + 2) delocalised electrons. Naphthalene, anthracene and phenanthrene all meet that condition, so none of them is non-aromatic and the answer is ‘None of the above’.
Correct answer: (D) More than one of the above
Conformations are shown both by sawhorse and by Newman projections, so the answer is ‘more than one’. An enantiomer is a matter of isomerism, not conformation.
Correct answer: (C) Glucose
Glucose has a free aldehyde group, so it reduces Tollens' reagent and gives the silver mirror. Cane sugar and starch are not reducing sugars.
Correct answer: (A) DDT
DDT is now banned, since it does not break down and goes on accumulating along the food chain.
Correct answer: (A) (CH₃)₂CHCl < CH₃CH₂Cl < CH₃Cl
In SN2 the nucleophile attacks from behind, so crowding lowers the reactivity—the increasing order is (CH₃)₂CHCl < CH₃CH₂Cl < CH₃Cl.
Correct answer: (C) Carbon
Lassaigne's test detects nitrogen, sulphur, halogens and phosphorus; carbon is detected by combustion instead.
Correct answer: (B) Trichloromethane
Trichloromethane—chloroform—is used in industry as a solvent for fats, waxes, resins and rubbers.
Correct answer: (C) p-Chlorobenzene
The para isomer is symmetrical and so packs well into the crystal lattice, which gives it the highest melting point.