Relevant Titles
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NCERT MCQs: Aromatic Compounds & Benzene — CBSE Class 11 Practice Quiz
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CBSE Class 11 Chemistry — Aromaticity, EAS & Benzene MCQs (NCERT)
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Aromatic Compounds and Benzene: 30 MCQs for CBSE Class 11 Board Prep
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Benzene & Substitution Reactions — Class 11 Chemistry Online Test
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Master Aromaticity & Electrophilic Substitution — CBSE Class 11 MCQs
Introduction
Prepare effectively for your CBSE Class 11 Chemistry exams with this focused NCERT-aligned practice set on Aromatic Compounds and Benzene (Chapter 13: Hydrocarbons — Part C: Organic Chemistry). This targeted quiz highlights the key concepts that frequently appear in board exams: aromaticity (Hückel’s rule), resonance stabilization, electrophilic aromatic substitution (nitration, sulfonation, halogenation, Friedel–Crafts reactions), directing effects of substituents, benzylic oxidation, and common reagents and mechanisms. Each MCQ is crafted to build conceptual clarity and exam confidence — from identifying activating vs deactivating groups to predicting directing positions and understanding intermediates like the arenium (Wheland) ion. Chemical formulas and reaction notations (for example, CO₂ and H₂O) are formatted clearly for easy reading. Use this timed 30-minute practice to gauge your strengths, get instant per-question feedback, and review concise explanations that map directly to NCERT learning objectives. Ideal as a revision tool before tests or daily practice, this resource helps convert understanding into reliable performance on the CBSE board exam.
Sample MCQs (with Answers & Explanations)
Q1. Which rule determines whether a cyclic conjugated π-system is aromatic?
A) 4n π electrons only
B) (4n + 2) π electrons (Hückel’s rule)
C) Any even number of π electrons
D) 2n π electrons
Answer: B — (4n + 2) π electrons (Hückel’s rule)
Explanation: Benzene (6 π electrons, n = 1) is aromatic because it is cyclic, planar, fully conjugated and satisfies Hückel’s (4n + 2) rule, giving extra stabilization.
Q2. Which reagent set is required to nitrate benzene to nitrobenzene?
A) HNO₃ alone at room temperature
B) HNO₃ + H₂SO₄ (conc., mixed acid)
C) Br₂/FeBr₃
D) KMnO₄ (hot)
Answer: B — Conc. HNO₃ + conc. H₂SO₄
Explanation: Mixed acid (HNO₃/H₂SO₄) generates the electrophile NO₂⁺, which attacks the aromatic ring in an electrophilic aromatic substitution (EAS) mechanism.
Q3. Which substituent is strongly deactivating and meta-directing on benzene?
A) –OCH₃ (methoxy)
B) –CH₃ (methyl)
C) –NO₂ (nitro)
D) –OH (hydroxyl)
Answer: C — –NO₂ (nitro)
Explanation: –NO₂ withdraws electron density by –I and –R effects, deactivating the ring and directing electrophiles to the meta position.
Q4. Why does benzene prefer electrophilic aromatic substitution (EAS) over electrophilic addition?
A) Addition is faster than substitution
B) Addition preserves aromaticity
C) Addition destroys aromatic stabilization (energetically costly)
D) Addition increases resonance stabilization
Answer: C — Addition destroys aromatic stabilization
Explanation: Electrophilic addition would break benzene’s delocalized π system and lose resonance energy; EAS temporarily disrupts aromaticity but restores it on deprotonation, so it’s favored.
Q5. Which reagent oxidizes a benzylic methyl group (–CH₃) on toluene to benzoic acid (–COOH)?
A) Dilute HCl
B) H₂ / Pd
C) KMnO₄ (hot, alkaline/acidic conditions)
D) Br₂ / FeBr₃
Answer: C — KMnO₄ (hot)
Explanation: Strong oxidants like hot KMnO₄ oxidize benzylic C–H to carboxyl groups (C₆H₅CH₃ → C₆H₅COOH), provided at least one benzylic hydrogen exists.