JEE Chemistry Hydrocarbons MCQs Set 03

Question. Statement-1 : 1-Butene on reaction with HBr in the presence of a peroxide produces 1-bromobutane.
Statement-2 : It involves the free radical mechanism.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question. Statement-1 : Iodination of alkanes is reversible.
Statement-2 : Iodination is carried out in presence of iodic acid.
(a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question. Statement-1 : CH₄ does not react with Cl2 in dark.
Statement-2 : Chlorination of CH₄ takes place in sunlight.
(a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(b) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct

Answer: A

Question. Statement-1 : All the hydrogen atoms in CH₂ = C = CH₂ lie in one plane.
Statement-2 : Carbon atoms are sp² and sp hybridized
(a) Assertion is incorrect, reason is correct.
(b) Assertion is correct, reason is correct; reason is a correct explanation for assertion
(c) None of these
(d) Assertion is incorrect, reason is correct

Answer: A

Question. The number of primary, secondary, tertiary and quaternary carbons in neopentane are respectively
(a) 4, 0, 0 and 1
(b) 4, 3, 2 and 1
(c) 5, 0, 0 and 1
(d) 4, 0, 1 and 1

Answer: A

Question. Which one of the following has the lowest boiling point?
(a) 2-methyl propane
(b) 2-methylbutane
(c) 2, 2-dimethyl propane
(d) n-pentane

Answer: A

Question.  Arrange the following in decreasing order of their boiling points.
(A) n–butane   (B) 2-methylbutane
(C) n-pentane  (D) 2, 2–dimethylpropane
(a) C > B > D > A
(b) B > C > D > A
(c) A > B > C > D
(d) D > C > B > A

Answer: A

Question. When neo-pentyl bromide is subjected to Wurtz reaction, the product formed is
(a) 2,2,5,5-tetramethylhexane
(b) 2,2,3,3-tetramethylhexane
(c) 2,2,4,4-tetramethylpentane
(d) 2,2,4,4-tetramethylhexane

Answer: A

Question. A hydrocarbon A on chlorination gives B which on heating with alcoholic potassium hydroxide changes into another hydrocarbon C. The latter decolourises Baeyer's reagent and on ozonolysis forms formaldehyde only. A is
(a) Ethane
(b) Butane
(c) Ethene
(d) Methane

Answer: A

Question. Which of the following compounds can yield only one monochlorinated product upon free radical chlorination?
(a) 2, 2-Dimethylpropane
(b) n-Butane
(c) Propane
(d) 2-Methylpropane

Answer: A

Question. The IUPAC name of the compound having the formula (CH₃)₃CCH = CH₂ is –
(a) 3, 3-dimethyl-1-butene
(b) 1, 1, 1-trimethyl-1-butene
(c) 3, 3, 3-trimethyl-1-propane
(d) None of these

Answer: A

Question. The number of possible open chain (acyclic) isomeric compounds for molecular formula C₅H₁₀ would be
(a) 6
(b) 8
(c) 7
(d) 5

Answer: A

Question. Correct order of stability is
(a) trans-2-butene > cis-2-butene > 1-butene
(b) 1-butene > cis-2-butene > trans-2- butene
(c) cis-2-butene > trans-2-butene > 1-butene
(d) cis -2- butene > 1-butene > trans -2-butene

Answer: A

Question. But-2-ene exhibits cis-trans-isomerism due to
(a) restricted rotation around C = C bond
(b) rotation around C₃ – C₄ sigma bond
(c) rotation around C₁ – C₂ bond
(d) None of these

Answer: A

Question. Aromatisation of n-hexane gives
(a) benzene
(b) toluene
(c) cyclohexane
(d) cycloheptane

Answer: A

Question. When 3, 3-dimethyl 2-butanol is heated with H₂SO₄, the major product obtained is
(a) 2,3-dimethyl 2-butene
(b) 3, 3-dimethyl 1- butene
(c) 2, 3-dimethyl 1- butene
(d) cis & trans isomers of 2, 3-dimethyl 2-butene

Answer: A

Question. Reaction of hydrogen bromide with propene in the absence of peroxide is a/an
(a) electrophilic addition
(b) electrophilic substitution
(c) nucleophilic addition
(d) free radical addition

Answer: A

Question. Which of the following types of reaction occur when a reactant has got a double bond ?
(i) Addition
(ii) Photolysis
(iii) Nucleophilic substitution
(iv) Polymerization
(a) (i) and (iv)
(b) (iii) and (iv)
(c) (i), (ii) and (iii)
(d) (ii) and (iii)

Answer: A

Question. The disappearance of the characteristic purple colour of KMnO₄ in its reaction with an alkene is the test for unsaturation. It is known as
(a) Baeyer test
(b) Grignard test
(c) Markownikoff test
(d) Wurtz test

Answer: A

Question. The only alcohol that can be prepared by the indirect hydration of alkene is
(a) Ethyl alcohol
(b) Propyl alcohol
(c) Isobutyl alcohol
(d) Methyl alcohol

Answer: A

Question. Which reactions are most common in alkenes
(a) Electrophilic addition reactions
(b) Nucleophilic addition reactions
(c) Nucleophillic substitution reactions
(d) Electrophilic substitution reactions

Answer: A

Question. In the presence of peroxide, hydrogen chloride and hydrogen iodide do not give anti-Markownikov’s addition to alkenes because
(a) One of the steps is endothermic in both the cases
(b) All the steps are exothermic in both the cases
(c) One is oxidising and the other is reducing
(d) Both are highly ionic

Answer: A

Question. Which of the following statements is incorrect regarding dehydrohalogenation of alkenes ?
(a) Only nature of halogen atom determine rate of the reaction
(b) Rate of reaction for same alkyl group; Iodine > Bromine > Chlorine
(c) Both
(d) None of these

Answer: A

Question. How many structural isomers are possible for the alkyne C₆H₁₀ ?
(a) 7
(b) 8
(c) 6
(d) 5

Answer: A

Question. Which of the following will have least hindered rotation around carbon - carbon bond ?
(a) Ethane
(b) Acetylene
(c) Ethylene
(d) Hexachloroethane

Answer: A

Question. Acetylenic hydrogens are acidic because
(a) Sigma electron density of C – H bond in acetylene is nearer to carbon, which has 50% s-character
(b) Acetylene has only open hydrogen in each carbon
(c) Acetylene contains least number of hydrogens among the possible hydrocarbons having two carbons
(d) None of these

Answer: A

Question. Propyne can be prepared by dehydrohalogenation of
(a) 1, 2–dichloropropane
(b) 1, 2–dichloroethane
(c) 1, 1, 2, 2–tetrachloroethane
(d) 1–chloropropane

Answer: A

Question. Which one of these is not compatible with arenes?
(a) Electrophilic additions
(b) Resonance
(c) Greater stability
(d) None of these

Answer: A

Question. The carbon-carbon bond length in benzene is
(a) In between C₂H₆ and C₂H₄
(b) In between C₂H₄ and C₂H₂
(c) Same as in C₂H₄
(d) None of these

Answer: A

Question. Point out the wrong statement in relation to the structure of benzene
(a) It forms only one monosubstitution product
(b) The C - C bond distance in benzene is uniformly 1.397Å
(c) It is a resonance hybrid of a number of canonical forms
(d) None of these

Answer: A

Question. (i) Chlorobenzene and (ii) benzene hexachloride are obtained from benzene by the reaction of chlorine, in the pesence of
(a) (i) Direct sunlight and (ii) anhydrous AlCl₃
(b) (i) Sodium hydroxide and (ii) sulphuric acid
(c) (i) Ultraviolet light and (ii) anhydrous FeCl₃
(d) (i) Anhydrous AlCl₃ and (ii) direct sunlight

Answer: A

Question. A group which deactivates the benzene ring towards electrophilic substitution but which directs the incoming group principally to the o- and p-positions is
(a) –Cl
(b) –C₂H₅
(c) –NH₂
(d) –NO₂

Answer: A

Question. Benzene can be obtained by heating either benzoic acid with X or phenol with Y. X and Y are respectively.
(a) Soda lime and zinc dust
(b) Zinc dust and soda lime
(c) Zinc dust and sodium hydroxide
(d) Soda lime and copper

Answer: A

Question. Which of the following statements is false for isopentane
(a) It has a carbon which is not bonded to hydrogen
(b) It has one CH group
(c) It has one CH₂ group
(d) None of these

Answer: A