Free Chemistry of Hydrocarbons MCQs with Answers
1,091 Chemistry of Hydrocarbons MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Hydrocarbons are studied through the structures and reactions of alkanes, alkenes, alkynes and aromatic compounds. Coverage includes free radical substitution in alkanes, electrophilic addition to carbon-carbon multiple bonds, benzene substitution, aromatic stability and the difference between addition reactions of alkenes and substitution reactions of benzene.
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Read the Chemistry of Hydrocarbons notesFree MDCAT chapter notes with key terms1,091 questions · page 6 of 55
- A. +I and +R effect
- B. -1 and +R effect
- C. +1 and -R effect
- D. -I and -R effect
Explanation: Chlorine withdraws electron density through sigma bonds because of its electronegativity, giving a -I effect.
Correct answer: -1 and +R effect- A. nitration
- B. halogenation
- C. sulphonation
- D. amination
Explanation: Nitration is the introduction of a nitro group, -NO2, into an organic molecule, commonly by treating an aromatic compound with…
Correct answer: nitration- A. Glycol
- B. Glyoxal
- C. Vicinal diol
- D. Both B & C
Explanation: Ozonolysis breaks the carbon-carbon bonds of benzene and produces three molecules of glyoxal, OHC-CHO.
Correct answer: Glyoxal- A. Oxidation
- B. Polymerization
- C. Dehydration
- D. Condensation
Explanation: Three acetylene molecules combine in a cyclic process to form one benzene molecule, so the reaction is a cyclotrimerisation, a type of…
Correct answer: Polymerization- A. Substitution reaction
- B. Addition reaction
- C. Elimination reaction
- D. Oxidation reaction
Explanation: Heating benzene with air over V2O5 oxidises the ring, commonly producing maleic anhydride, so the reaction is an oxidation reaction.
Correct answer: Oxidation reaction- A. NO3
- B. NO
- C. NO2-
- D. NO2+
Explanation: The nitronium ion is NO2+, formed in the nitrating mixture from nitric acid and sulfuric acid, and it acts as the electrophile in benzene…
Correct answer: NO2+- A. Substitution reaction
- B. Addition reaction
- C. Polymerization reactions
- D. Oxidation reactions
Explanation: Benzene commonly undergoes electrophilic substitution and can undergo addition or oxidation under appropriate severe or catalytic…
Correct answer: Polymerization reactions- A. diphenyl amine
- B. diphenyl methane
- C. naphthalene
- D. biphenyl
Explanation: Naphthalene is a fused cyclic aromatic compound because two benzene rings share a pair of adjacent carbon atoms and form one fused ring…
Correct answer: naphthalene- A. acetylene
- B. N-hexane
- C. Benzene sulphonic acid
- D. Sodium benzoate
Explanation: N-hexane undergoes catalytic dehydrocyclisation, losing hydrogen and forming a six-membered aromatic ring, benzene.
Correct answer: N-hexane- A. Specific gravity method
- B. Vapour density method
- C. X-ray diffraction method
- D. Distillation methos
Explanation: Vapour density is related to molecular mass by molecular mass = 2 x vapour density when the vapour is measured relative to hydrogen.
Correct answer: Vapour density method- A. o - chloronitrobenzene
- B. p - chloronitrobenzene
- C. m - chloronitrobenzene
- D. A & B
Explanation: Chlorine is deactivating but ortho-para directing because its lone pairs can donate by resonance into the benzene ring.
Correct answer: A & B- A. Glyoxime
- B. Benzaldehyde
- C. Glycol
- D. Glyoxal
Explanation: Benzene adds three ozone molecules, one across each of its three double-bond equivalents, and hydrolysis of the ozonide produces 3 moles…
Correct answer: Glyoxal- 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.