Free Benzene and Aromatic Compounds MCQs with Answers
172 Benzene and Aromatic Compounds MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Benzene has a planar ring of delocalised π electrons, giving aromatic stability and equal carbon-carbon bond lengths. The topic covers resonance, electrophilic substitution reactions such as nitration, halogenation, sulphonation and Friedel-Crafts reactions, along with substituent effects and the distinction between substitution in benzene and addition in ordinary alkenes.
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172 questions · page 2 of 9
- A. C6H6O9
- B. C6H5O8
- C. C6H5O9
- D. C6H6O6
Explanation: Each of the three ozone molecules adds three oxygen atoms to benzene, so C6H6 + 3O3 gives the ozonide formula C6H6O9.
Correct answer: C6H6O9- A. Toluene
- B. Ethyl benzene
- C. n-propyl benzene
- D. All
Explanation: Strong oxidation of an alkylbenzene with acidified KMnO4 or K2Cr2O7 converts the entire side chain into a carboxyl group, provided the…
Correct answer: All- A. Dows process
- B. Friedel & Craft acylation
- C. Friedel & Craft alkylation
- D. Clemmenson reduction
Explanation: Friedel-Crafts alkylation replaces a hydrogen atom of benzene with an alkyl group using an alkyl halide and a Lewis acid such as AlCl3.
Correct answer: Friedel & Craft alkylation- A. On hydrogenation 208 KJ/mole is liberated
- B. C-H bond length in benzene is 1.09 A?
- C. Molecular mass of benzene is 78.108
- D. Resonance energy of benzene is 150.5 K Cal/mole
Explanation: Benzene has a hydrogenation enthalpy of about 208 kJ/mol, C-H bonds of about 1.09 A, and a molecular mass of about 78.108 g/mol.
Correct answer: Resonance energy of benzene is 150.5 K Cal/mole- A. Benzene
- B. Nitro benzene
- C. Toluene
- D. Chlorobenzene
Explanation: The methyl group in toluene donates electron density to the benzene ring and activates it towards electrophilic substitution, making…
Correct answer: Toluene- A. HSO4-
- B. SO2
- C. SO3
- D. H+
Explanation: In concentrated sulfuric acid or oleum, sulfur trioxide, SO3, acts as the electrophile that attacks the benzene ring during sulphonation.
Correct answer: SO3- A. The rupturing of benzene ring
- B. Substitution reaction
- C. Addition reaction
- D. No-reaction
Explanation: In sunlight, bromine can add to benzene through a photochemical reaction, producing benzene hexabromide rather than undergoing the usual…
Correct answer: Addition reaction- A. Heating sod. Salt of Benzoic acid with soda lime
- B. Distilling phenol with Zn dust
- C. Chlorobenzene with NaOH at 360°C & 150atm.
- D. Hydrolysis of benzene sulphonic acid with super heated steam
Explanation: Chlorobenzene treated with NaOH at about 360°C and 150 atm gives sodium phenoxide, which produces phenol on acidification, not benzene.
Correct answer: Chlorobenzene with NaOH at 360°C & 150atm.- A. Cr2O3 + A2O3 + SiO2
- B. Raney nickel
- C. Organo-nickel
- D. Ni 250 - 300°C
Explanation: At about 70°C, acetylene can undergo cyclotrimerisation to form benzene in the presence of an organo-nickel catalyst.
Correct answer: Organo-nickel- A. 150.5 kJ/mol
- B. 250.5 kJ/mol
- C. 150.5 Cal/mol
- D. 250.5 Cal/mol
Explanation: The resonance energy of benzene is approximately 150.5 kJ/mol, representing the extra stability caused by delocalisation of its pi…
Correct answer: 150.5 kJ/mol31. How many moles of H2 are added up when benzene is heated with hydrogen in the presence of platinum ?
- A. Two
- B. Three
- C. Four
- D. Six
Explanation: Complete catalytic hydrogenation converts benzene, C6H6, into cyclohexane, C6H12: C6H6 + 3H2 -> C6H12.
Correct answer: Three- A. The presence of Oxygen
- B. The presence of Hydrogen
- C. The absence of Oxygen
- D. The presence of excessive Oxygen
Explanation: Destructive distillation heats vegetable oil strongly in the absence of oxygen, causing decomposition into smaller substances including…
Correct answer: The absence of Oxygen- A. 3
- B. 4
- C. 6
- D. 8
Explanation: Each of benzene's three p orbitals contributes a pair of pi electrons to the delocalised electron cloud, giving 3 x 2 = 6 delocalised…
Correct answer: 6- A. Two
- B. Three
- C. Four
- D. Five
Explanation: Phenanthrene is made of three fused benzene rings arranged in an angular structure.
Correct answer: Three- A. Aliphatic
- B. Alicyclic
- C. Aromatic
- D. Aldehyde
Explanation: Aromatic hydrocarbons have a relatively high carbon-to-hydrogen ratio, so incomplete combustion often produces glowing carbon particles…
Correct answer: Aromatic- A. Chlorobenzene
- B. Toluene
- C. Nitrobenzene
- D. Benzene
Explanation: The methyl group in toluene releases electron density into the benzene ring by induction and hyperconjugation, activating it towards…
Correct answer: Toluene- A. Phenol
- B. Maleic anhydride
- C. Glyoxal
- D. Benzoic acid
Explanation: Vapour-phase oxidation of benzene with air over V2O5 at about 450°C cleaves the ring and produces maleic anhydride.
Correct answer: Maleic anhydride- A. fats
- B. resins
- C. iodine
- D. all the above
Explanation: Benzene is a non-polar organic solvent, so it dissolves largely non-polar substances such as fats, many resins and iodine.
Correct answer: all the above- A. Cyclohexane
- B. Heterocyclic
- C. Alicyclic
- D. Unsaturated aliphatic
Explanation: Reduction of benzene in the presence of nickel (Ni) results in the formation of cyclohexane.
Correct answer: Cyclohexane- A. AlCl3
- B. HNO3
- C. BeCl2
- D. NaCl
Explanation: Aluminium trichloride (AlCl3) is often used as a catalyst in Friedel-Crafts reactions since it acts as a Lewis acid and coordinates with…
Correct answer: AlCl3