Hydrocarbons is a Class 11 Chemistry chapter that carries about 4.4% of the Chemistry questions in NEET. Practise it with 47 questions covering 2 topics, each with an explanation.
Sample questions on Hydrocarbons with answers
8 questions from the practice bank, spread across the chapter's topics. The full set is in the app.
Question 1: Markovnikov's Rule
Chlorobenzene undergoes further substitution at the ortho and para positions even though the ring is deactivated because chlorine:
- A is a strong donor of electrons
- B is a bulky group
- C withdraws electrons by the –I effect, but its lone pair donates electrons by the +R effect to those positions
- D is not electronegative
Answer: C. withdraws electrons by the –I effect, but its lone pair donates electrons by the +R effect to those positions
Why: The inductive effect dominates the overall reactivity, but the resonance effect controls the orientation.
Question 2: Nomenclature of Alkanes, Alkenes and Alkynes
Among the following alkenes, the most stable is:
- A ethene
- B propene
- C 2,3-dimethylbut-2-ene
- D but-1-ene
Answer: C. 2,3-dimethylbut-2-ene
Why: Stability increases with the number of alkyl groups on the double bond (hyperconjugation).
Question 3: Markovnikov's Rule
The peroxide effect is observed only with:
- A HBr
- B HF
- C HCl
- D HI
Answer: A. HBr
Why: For HCl and HI, one of the chain steps is energetically unfavourable.
Question 4: Nomenclature of Alkanes, Alkenes and Alkynes
The IUPAC name of CH₃–CH(CH₃)–CH₂–CH₃ is:
- A 2-ethylpropane
- B 2-methylbutane
- C isopentane only
- D 3-methylbutane
Answer: B. 2-methylbutane
Why: The longest chain has four carbons (butane) with a methyl on carbon 2.
Question 5: Markovnikov's Rule
Friedel–Crafts acylation of benzene with CH₃COCl and anhydrous AlCl₃ gives:
- A benzaldehyde
- B benzoic acid
- C toluene
- D acetophenone
Answer: D. acetophenone
Why: An acyl group replaces a hydrogen.
Question 6: Nomenclature of Alkanes, Alkenes and Alkynes
The acidity of hydrocarbons follows the order:
- A ethyne > ethene > ethane
- B ethene > ethyne > ethane
- C ethane > ethene > ethyne
- D all equal
Answer: A. ethyne > ethene > ethane
Why: A greater s-character makes the carbon more electronegative.
Question 7: Markovnikov's Rule
Benzene reacts with chlorine in bright sunlight, without a catalyst, to give:
- A no reaction
- B dichlorobenzene
- C benzene hexachloride (BHC), by addition
- D chlorobenzene
Answer: C. benzene hexachloride (BHC), by addition
Why: Free radicals add to the ring.
Question 8: Nomenclature of Alkanes, Alkenes and Alkynes
On heating 2-bromobutane with alcoholic KOH, the major product is:
- A butan-2-ol
- B but-1-ene
- C butane
- D but-2-ene (Saytzeff's rule)
Answer: D. but-2-ene (Saytzeff's rule)
Why: The more substituted alkene is the more stable and is formed in greater amount.
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