Hydrocarbons NEET Previous Year Questions (PYQs)
Practice NEET previous year questions from Hydrocarbons. These MCQs cover alkanes, alkenes, alkynes, benzene, aromaticity, conformations, electrophilic substitution and important reactions with answers and clear explanations.
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Hydrocarbons Chapter Notes
Q1. Hydrocarbon (A) reacts with bromine by substitution to form an alkyl bromide which on Wurtz reaction gives a gaseous hydrocarbon containing less than four carbon atoms. (A) is:
(NEET 2018)
- (A) Ethane
- (B) Propane
- (C) n-Butane
- (D) Methane
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(D)
Show Explanation
Methane gives methyl bromide, which on Wurtz reaction forms ethane (C2H6).
Q2. Correct order of acidity is:
(NEET 2017)
- (A) Alkynes > Alkenes > Alkanes
- (B) Alkanes > Alkenes > Alkynes
- (C) Alkenes > Alkynes > Alkanes
- (D) Alkanes > Alkynes > Alkenes
Show Answer
(A)
Show Explanation
Acidity increases with % s-character: sp > sp2 > sp3.
Q3. With respect to conformers of ethane, which statement is true?
(NEET 2017)
- (A) Bond angle changes
- (B) Bond length changes
- (C) Both bond angle and bond length remain same
- (D) Both change
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(C)
Show Explanation
Only torsional angle changes; bond length and bond angle remain same.
Q4. Which halide can be used in Friedel–Crafts alkylation?
(NEET 2016)
- (A) Chlorobenzene
- (B) Bromobenzene
- (C) Chloroethene
- (D) Isopropyl chloride
Show Answer
(D)
Show Explanation
Aryl and vinyl halides do not undergo Friedel–Crafts reaction.
Q5. Staggered conformation of ethane is more stable because:
(NEET 2016)
- (A) Bond angle increases
- (B) Bond length decreases
- (C) It has no torsional strain
- (D) It has steric strain
Show Answer
(C)
Show Explanation
Staggered form has minimum repulsion between bonding electrons.
Q6. Which compound is most reactive towards electrophilic aromatic substitution?
(NEET 2020)
- (A) Nitrobenzene
- (B) Benzene
- (C) Chlorobenzene
- (D) Phenol
Show Answer
(D)
Show Explanation
–OH group strongly activates benzene ring by +R effect.
Q7. Which reaction is a free-radical substitution reaction?
(NEET 2020)
- (A) Benzene + Br2/AlCl3
- (B) Acetylene + HBr
- (C) Methane + Br2/hv
- (D) Propene + HBr
Show Answer
(C)
Show Explanation
Alkanes undergo substitution via free-radical mechanism.
Q8. Dihedral angle in staggered form of ethane is:
(NEET 2000)
- (A) 0°
- (B) 60°
- (C) 120°
- (D) 180°
Show Answer
(B)
Show Explanation
Staggered conformation has maximum separation of H-atoms (60°).
Q9. Which alkene shows geometrical isomerism?
(NEET 2009)
- (A) 1-Butene
- (B) 2-Butene
- (C) 2-Butyne
- (D) Propene
Show Answer
(B)
Show Explanation
2-Butene has restricted rotation and different groups on both carbons.
Q10. Which compound has zero dipole moment?
(NEET 1996)
- (A) cis-2-Butene
- (B) 1-Butene
- (C) 2-Methylpropene
- (D) trans-2-Butene
Show Answer
(D)
Show Explanation
Dipole moments cancel in symmetrical trans-isomer.
Q11. Acetylenic hydrogen is acidic because:
(NEET 1989)
- (A) High s-character
- (B) Low bond energy
- (C) Fewer hydrogens
- (D) Triple bond
Show Answer
(A)
Show Explanation
sp-hybridised carbon is more electronegative.
Q12. Which reagent distinguishes 1-butyne from 2-butyne?
(NEET 2010)
- (A) Ammoniacal AgNO3
- (B) HCl
- (C) Br2
- (D) KMnO4
Show Answer
(A)
Show Explanation
Terminal alkynes form silver acetylide precipitate.
Q13. Reactive electrophile in nitration of benzene is:
(NEET 1994)
- (A) NO2
- (B) NO2+
- (C) HNO3
- (D) HNO2
Show Answer
(B)
Show Explanation
Nitronium ion is the actual attacking species.
Q14. Most stable alkene is:
(NEET 2000)
- (A) 1-Butene
- (B) cis-2-Butene
- (C) trans-2-Butene
- (D) All equal
Show Answer
(C)
Show Explanation
Trans-isomer has minimum steric repulsion.
Q15. Which hydrocarbon is desirable in petrol for high octane number?
(NEET 1997)
- (A) Straight chain
- (B) Linear alkene
- (C) Branched hydrocarbon
- (D) Alkyne
Show Answer
(C)
Show Explanation
Branched hydrocarbons burn smoothly.
Q16. Benzene reacts with CH3Cl in presence of AlCl3 to form:
(NEET 2009)
- (A) Chlorobenzene
- (B) Benzyl chloride
- (C) Xylene
- (D) Toluene
Show Answer
(D)
Show Explanation
This is Friedel–Crafts alkylation.
Q17. Which compound does NOT undergo Friedel–Crafts reaction easily?
(NEET 2013)
- (A) Nitrobenzene
- (B) Toluene
- (C) Xylene
- (D) Cumene
Show Answer
(A)
Show Explanation
–NO2 group strongly deactivates benzene.
Q18. Reaction of HBr with propene in presence of peroxide gives:
(NEET 2004)
- (A) Isopropyl bromide
- (B) Allyl bromide
- (C) n-Propyl bromide
- (D) tert-Butyl bromide
Show Answer
(C)
Show Explanation
Anti-Markovnikov addition occurs in presence of peroxide.
Q19. Reduction of 2-butyne with Na/liquid NH3 gives:
(NEET 1993)
- (A) cis-2-Butene
- (B) trans-2-Butene
- (C) Butane
- (D) No reaction
Show Answer
(B)
Show Explanation
Birch reduction gives trans-alkene.
Q20. Benzene is aromatic because:
(NEET 1992)
- (A) It undergoes addition
- (B) It has alternating bonds
- (C) It has delocalised π-electrons
- (D) It is planar only
Show Answer
(C)
Show Explanation
Delocalisation of π-electrons gives extra stability.
👉 More Hydrocarbons NEET PYQs will be added gradually.