Hydrocarbons MCQ for NEET PDF with Answers | Class 11 & 12 | Previous Year Questions
Mastering Hydrocarbons MCQ for NEET? This high-weightage chapter fuels 4-5 questions in the exam! Our free Hydrocarbons MCQ PDF covers Class 11 and 12, packed with 100+ questions, answers, and previous year NEET questions. Designed for NCERT-focused prep, it drills into alkanes, alkenes, alkynes, aromatic compounds, reaction mechanisms (Markovnikov, ozonolysis), and isomerism.
Each MCQ includes detailed solutions to clarify concepts like carbocation stability or electrophilic substitution. Download the Hydrocarbons MCQs with answers PDF for offline practice or try our online MCQ test for instant scoring. Perfect for last-minute revision, self-assessment, or spotting NEET’s trick questions (e.g., “Which reagent distinguishes alkynes from alkenes?”). No signup or fees! Boost your organic chemistry score today.
Hydrocarbons MCQ for NEET PDF with Answers | Class 11 & 12 | Previous Year Questions
Practicing these MCQ on Hydrocarbons for NEET will help you to answer every question that is being asked in the board exams as well as in NEET Exam also. Students can solve these Hydrocarbons MCQ for NEET Pdf Download to know their preparation level. Hydrocarbons Objective type Questions help the students to understand the concepts thoroughly and to score good marks in NEET. The below Multiple Choice Questions on Hydrocarbons with answers Pdf have been prepared as per the latest syllabus. Practice it now and score high in NEET exam.
1. The order of reactivity of alkyl halides in Wurtz reaction is__________
(1) R–I > R–Br > R–Cl
(2) R–I < R–Br < R–Cl
(3) R–Br > R–I < R–Cl
(4) R–I > R–Cl > R–Br
Answer: 1
Explanation: In the Wurtz reaction, the reactivity of alkyl halides depends on the bond strength between carbon and the halogen. C–I bond is weakest, making iodoalkanes most reactive, followed by bromo- and then chloro-alkanes.
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2. Reduction of aldehydes and ketones into hydrocarbons using zinc amalgam and conc. HCl is called_____
(1) Cope reduction
(2) Dow reduction
(3) Wolf-Kishner reduction
(4) Clemmensen reduction
Answer: 4
Explanation: Clemmensen reduction uses Zn-Hg (zinc amalgam) and concentrated HCl to convert aldehydes and ketones into alkanes under acidic conditions.
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3. Which of the compounds with molecular formula C₅H₁₀ yields acetone on ozonolysis_________
(1) 3-Methyl-1-butene
(2) Cyclopentene
(3) 2-Methyl-1-butene
(4) 2-Methyl-2-butene
Answer: 4
Explanation: Ozonolysis of 2-Methyl-2-butene cleaves the double bond to give two identical molecules of acetone, as both sides of the double bond are symmetrically substituted.
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4. Kolbe’s electrolysis of a mixture of potassium propanoate and potassium 3-methylbutanoate gives______
(1) Butane and isobutane
(2) Butane and 2,5–dimethylhexane
(3) Butane, 2,5-dimethylhexane and isohexane
(4) Butane and isohexane
Answer: 3
Explanation: Kolbe’s electrolysis involves decarboxylation and radical coupling. Mixing two different carboxylic acids gives three products due to possible combinations of radicals: homocoupling and cross-coupling products.
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5. The Corey-House alkane synthesis is carried out by treating an alkyl halide with________
(1) Lithium metal
(2) Copper metal
(3) Lithium metal followed by reaction with cuprous iodide and then treating the product with an alkyl halide
(4) Cuprous iodide followed by reaction with alkyl halide
Answer: 3
Explanation: Corey-House synthesis involves conversion of alkyl halide to lithium dialkyl cuprate using lithium metal and CuI, followed by coupling with another alkyl halide to form alkanes.
6. Which of the following acids on decarboxylation gives isobutane________
(1) 2,2–Dimethyl butanoic acid
(2) 2,2–dimethyl propanoic acid
(3) 3–Methyl pentanoic acid
(4) 2–Methyl butanoic acid
Answer: 2
Explanation: 2,2-Dimethylpropanoic acid, upon decarboxylation, gives isobutane (CH₃)₃CH by removal of the –COOH group.
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7. Which of the following compound is not suitable to obtain from Wurtz reaction?
(1) Ethane
(2) Butane
(3) Isobutane
(4) Hexane
Answer: 3
Explanation: Wurtz reaction works best for symmetrical alkanes. Isobutane (a branched alkane) cannot be obtained using a single alkyl halide due to difficulty in selective formation via radical pathway.
8. When ethyl chloride and n-propyl chloride undergo Wurtz reaction, which is not obtained________
(1) n-butane
(2) n-pentane
(3) n-hexane
(4) isobutane
Answer: 4
Explanation: Ethyl and n-propyl radicals can combine to give n-butane, n-pentane, and n-hexane. Isobutane, being branched, cannot be formed from this combination.
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9. Kolbe’s electrolysis of sodium maleate at anode gives__________
(1) Only acetylene
(2) Only CO₂
(3) Acetylene + CO₂
(4) CO₂ + H₂
Answer: 3
Explanation: Sodium maleate undergoes decarboxylation during Kolbe’s electrolysis to yield acetylene and carbon dioxide as products at the anode.
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10. The pH of solution in Kolbe’s electrolysis___________
(1) Increases with time
(2) Decreases with time
(3) Remains constant
(4) Nothing can be said
Answer: 1
Explanation: During Kolbe’s electrolysis, OH⁻ ions are formed at the cathode, increasing the pH of the solution over time (making it more basic).
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11. Which of the following compound will not give a precipitate with Tollen’s reagent_____
(1) ethyne
(2) 1-butyne
(3) 3-methyl-1-butyne
(4) 1-pentene
Answer: 4
Explanation: Tollen’s reagent gives a positive test with terminal alkynes and aldehydes. 1-pentene is an alkene and does not react with Tollen’s reagent.
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12. Liquid hydrocarbons can be converted to a mixture of gaseous hydrocarbons by______
(1) Hydrolysis
(2) Oxidation
(3) Cracking
(4) Distillation under reduced pressure
Answer: 3
Explanation: Cracking is a thermal decomposition process where large hydrocarbon molecules are broken into smaller gaseous molecules like ethene and propene.
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13. Benzene is________
(1) Weakly attracted in the magnetic field
(2) Strongly attracted in the magnetic field
(3) Strongly repelled in magnetic field
(4) Weakly repelled in magnetic field
Answer: 4
Explanation: Benzene is aromatic and non-polar; it is weakly repelled by a magnetic field due to its delocalized π-electrons.
14. The oxidation of benzene by V₂O₅ in the presence of air produces________
(1) Benzoic acid
(2) Benzaldehyde
(3) Benzoic anhydride
(4) Maleic anhydride
Answer: 4
Explanation: In the presence of vanadium pentoxide (V₂O₅) and air, benzene undergoes oxidation to form maleic anhydride, an important industrial product.
15. Ozonolysis of 3–Methyl–1–butene gives a mixture of_____
(1) Propanal and ethanal
(2) Propanone and ethanal
(3) 2–Methylpropanal and methanal
(4) Butanone and methanal
Answer: 3
Explanation: Ozonolysis cleaves the double bond in 3-Methyl-1-butene to yield 2-Methylpropanal and methanal as products.
16. Which alkene gives acetone only on ozonolysis______
(1) Isobutylene
(2) 2,3–Dimethyl–1–butene
(3) 2,3–Dimethyl–2–butene
(4) 3,3–Dimethyl–1–butene
Answer: 3
Explanation: 2,3-Dimethyl-2-butene on ozonolysis gives two identical molecules of acetone due to symmetric substitution around the double bond.
17. Oxidation of isobutylene with acidified potassium permanganate gives________
(1) Acetone + CO₂
(2) Acetic acid
(3) Acetic acid + CO₂
(4) Acetic acid + acetone
Answer: 1
Explanation: Oxidation of isobutylene with KMnO₄ cleaves the double bond, giving acetone and carbon dioxide as products.
18. Which of the following reactions is used for locating the position of double bond in an alkene_________
(1) Hydroboration
(2) Hydroxylation
(3) Chlorohydroxylation
(4) Ozonolysis
Answer: 4
Explanation: Ozonolysis cleaves the double bond, and the nature of resulting carbonyl compounds helps determine the original position of the double bond.
19. Which one of the following has the smallest heat of hydrogenation per mole_____________
(1) 1–butene
(2) Trans–2–butene
(3) Cis–2–butene
(4) Propene
Answer: 2
Explanation: Trans-2-butene is more stable than its cis-isomer and other alkenes listed, so it has the lowest heat of hydrogenation.
20. The volume of methane evolved by treatment of 16.6 g of methyl magnesium iodide with water at S.T.P. is________
(1) 224 mL
(2) 2.24 L
(3) 0.224 L
(4) 22.4 L
Answer: 2
Explanation: One mole of CH₃MgI gives one mole of CH₄. 16.6 g corresponds to 0.1 mol, which gives 2.24 L of methane at STP (0.1 × 22.4 L).
21. The molecules having dipole moment are________
(1) 2,2-dimethylpropane
(2) trans-pent-2-ene
(3) cis-hex-3-ene
(4) 2 and 3
Answer: 4
Explanation: Trans isomers have zero dipole moment due to symmetry, but cis-isomers like cis-hex-3-ene are polar. Trans-pent-2-ene is slightly polar due to alkyl chain asymmetry. Hence, both 2 and 3 show dipole moments.
22. The highest boiling point is expected for__________
(1) Isooctane
(2) 2,2,3,3-tetramethylbutane
(3) n-octane
(4) n-butane
Answer: 3
Explanation: Straight-chain alkanes like n-octane have greater surface area and intermolecular van der Waals forces, leading to higher boiling points than branched isomers.
23. Pyrolysis of alkanes is a____________
(1) Nucleophilic addition reaction
(2) Free radical substitution reaction
(3) Electrophilic addition reaction
(4) Free radical elimination reaction
Answer: 4
Explanation: Pyrolysis or cracking involves breaking C–C and C–H bonds via free radicals, leading to elimination and formation of alkenes and smaller alkanes.
24. Which of the following does not give alkane with R—Mg—X.
(1) Ph—OH
(2) C₆H₆
(3) CH₃COOH
(4) HCl
Answer: 2
Explanation: Benzene (C₆H₆) is not acidic enough to react with Grignard reagent (R–Mg–X) to give alkane, unlike phenol, carboxylic acid, and HCl which can donate protons.
25. Which of the following reaction can not be used to obtain propane in good yield________
(1) Wurtz reaction
(2) Corey-House reaction
(3) Decarboxylation of acid salt
(4) All of them
Answer: 1
Explanation: Wurtz reaction yields symmetrical alkanes. Propane is an unsymmetrical alkane and cannot be prepared in good yield using a single alkyl halide by this method.
26. The compound with the highest boiling point is_________
(1) n-hexane
(2) n-pentane
(3) 2,2-dimethylpropane
(4) propane
Answer: 1
Explanation: Longer straight-chain alkanes like n-hexane have greater surface area and intermolecular forces, resulting in higher boiling points than shorter or branched alkanes.
27. Photochemical chlorination of alkane is initiated by a process of_________
(1) Pyrolysis
(2) Substitution
(3) Homolysis
(4) Peroxidation
Answer: 3
Explanation: UV light breaks Cl–Cl bond homolytically to form chlorine radicals that initiate the chain reaction in photochemical chlorination of alkanes.
28. Isomerization in alkane may be brought about by using_______
(1) Al₂O₃
(2) Fe₂O₃
(3) AlCl₃ and HCl
(4) Concentrated H₂SO₄
Answer: 3
Explanation: Isomerization of alkanes is catalyzed by Lewis acid (AlCl₃) in the presence of HCl, converting straight-chain alkanes into branched isomers.
29. Bromination of an alkane as compared to chlorination proceeds___________
(1) At a slower rate
(2) At a faster rate
(3) With equal rates
(4) With equal or different rate depends upon the temperature
Answer: 1
Explanation: Bromination is slower than chlorination because bromine radicals are less reactive. However, it is more selective in hydrogen abstraction.
30. An alkene on treating with hot acidified KMnO₄ gives 4-oxopentanoic acid. The alkene is_________
(1) Pentene
(2) 2–Pentene
(3) 1–Methylcyclobutene
(4) 1,2–Dimethylcyclopropene
Answer: 3
Explanation: 1-Methylcyclobutene upon oxidative cleavage with hot KMnO₄ gives 4-oxopentanoic acid due to ring opening and oxidation of double bond.
31. The addition of Br₂ to cis–2–butene produces____________
(1) (+)–2,3–dibromobutane only
(2) (–)–2,3–dibromobutane only
(3) racemic–2,3–dibromobutane
(4) meso–2,3–dibromobutane
Answer: 4
Explanation: Addition of Br₂ to cis–2–butene occurs via anti-addition mechanism leading to a meso compound due to symmetry and internal compensation of optical activity.
32. Which of the following reactions does not involve a C—C bond formation_________
(1) Hydrolysis of a Grignard reagent
(2) Combination of two alkyl free radicals
(3) Corey-House synthesis of alkanes
(4) RNa + R–Br → R–R + NaBr
Answer: 1
Explanation: Hydrolysis of Grignard reagent produces alkanes but does not involve carbon–carbon bond formation. Other reactions listed result in C–C bond formation.
33. If two moles of isopropyl chloride react with Na in presence of dry ether, which alkane is obtained__________
(1) Hexane
(2) 2,3-Dimethylbutane
(3) Isopentane
(4) Neopentane
Answer: 2
Explanation: Wurtz reaction of isopropyl chloride leads to coupling of two isopropyl groups, forming 2,3-dimethylbutane, a branched alkane.
34. If isopropyl chloride and ethyl chloride both react with Na in presence of dry ether, which alkanes are obtained__________
(1) n-Butane
(2) 2-Methylbutane
(3) 2,3-Dimethylbutane
(4) All of them
Answer: 4
Explanation: Cross and self-coupling of isopropyl and ethyl radicals give multiple products including n-butane (from ethyl-ethyl), 2-methylbutane (from ethyl-isopropyl), and 2,3-dimethylbutane (from isopropyl-isopropyl).
35. Which of the following compound can not be obtained from single alkyl halide by Wurtz reaction________
(1) Ethane
(2) Butane
(3) Isobutane
(4) Hexane
Answer: 3
Explanation: Wurtz reaction with a single alkyl halide gives symmetrical alkanes. Isobutane is a branched unsymmetrical compound, thus cannot be obtained from a single halide.
36. How many acids can be taken to obtain isobutane by decarboxylation ?
(1) 4
(2) 3
(3) 2
(4) 5
Answer: 3
Explanation: Decarboxylation of certain branched carboxylic acids like 2,2-dimethylpropanoic acid and two others can lead to isobutane. A total of 3 acids are commonly known.
37. When ethene reacts with bromine in aqueous sodium chloride solution, the product(s) obtained is (are)___________
(1) Ethylene dibromide only
(2) Ethylene dibromide and 1–bromo–2–chloroethane
(3) 1–bromo–2–chloroethane only
(4) Ethylene dichloride only
Answer: 2
Explanation: In aqueous NaCl, Br₂ forms bromonium ion intermediate. Nucleophilic attack by both Br⁻ and Cl⁻ yields a mixture of ethylene dibromide and bromo-chloroethane.
38. A compound having a bond angle 180° is__________
(a) Alkyne
(b) Alkane
(c) Alkene
(d) Cycloalkane
Answer: 1
Explanation: Alkynes have a linear geometry due to sp hybridization of carbon atoms in the triple bond, leading to a bond angle of 180°.
39. Which one of these is not true for benzene?
(1) There are three carbon–carbon single bonds and three carbon–carbon double bonds
(2) Heat of hydrogenation of benzene is less than the theoretical value
(3) It forms only one type of mono-substituted product
(4) The bond angle between carbon–carbon bonds is 120°
Answer: 1
Explanation: Benzene has six equivalent C–C bonds due to delocalized π electrons, not alternating single and double bonds. Hence, statement 1 is incorrect.
40. Presence of a nitro group in a benzene ring____________
(1) Activates the ring towards electrophilic substitution
(2) Renders the ring basic
(3) Deactivates the ring towards nucleophilic substitution
(4) Deactivates the ring towards electrophilic substitution
Answer: 4
Explanation: The nitro group is an electron-withdrawing group that deactivates the aromatic ring toward electrophilic substitution by reducing electron density.
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