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.
Last updated
Read the Chemistry of Hydrocarbons notesFree MDCAT chapter notes with key terms1,091 questions · page 17 of 55
- A. 2-Butene
- B. Ethene
- C. 2-Methyl-2-Butene
- D. Propene
Explanation: The reactivity of alkenes towards electrophilic addition generally decreases as substitution increases.
Correct answer: Ethene- A. 2
- B. 3
- C. 4
- D. 5
Explanation: The molecular formula C7H8O corresponds to toluene derivatives with a-OH group (methylphenols) or benzaldehyde.
Correct answer: 4- A. Non thermic reaction
- B. Exothermic reaction
- C. Endothermic reaction
- D. None
Explanation: The Sabatier-Senderens reaction is the catalytic hydrogenation of unsaturated hydrocarbons.
Correct answer: Exothermic reaction- A. But-1-yne
- B. But-1-ene
- C. But-2-yne
- D. But-2-ene
Explanation: Ammoniacal silver nitrate (Tollens reagent) reacts specifically with terminal alkynes, which have an acidic hydrogen atom on a…
Correct answer: But-1-yne- A. 2-Methylpropene > Propene > Ethene
- B. Ethene > Propene > 2-Methylpropene
- C. Propene > Ethene > 2-Methylpropene
- D. Ethene > 2-Methylpropene > Propene
Explanation: The reaction proceeds via a carbocation intermediate. The more stable the carbocation formed, the faster the reaction.
Correct answer: 2-Methylpropene > Propene > Ethene- A. Baeyer's reagent
- B. Ammonical AgNO3
- C. Br2 solution
- D. O3, Zn / H2O
Explanation: Ozonolysis cleaves the double bond and can be used to determine its location.
Correct answer: O3, Zn / H2O- A. Both are highly ionic
- B. One is oxidizing and the other is reducing
- C. One of the steps in the free radical mechanism is endothermic
- D. All the steps are exothermic in both cases
Explanation: The anti-Markovnikov addition proceeds via a fraa-radical mechanism. For HCI and Hl, one of the chain propagation steps is highly…
Correct answer: One of the steps in the free radical mechanism is endothermic- A. Ethene
- B. Ethane
- C. Ethyne
- D. Methane
Explanation: Kolbe's electrolysis of the salt of an unsaturated dicarboxylic acid like maleic acid involves decarboxylation and radical formation at…
Correct answer: Ethyne- A. Alkene
- B. Alkyne
- C. Alkane
- D. Amine
Explanation: The Wolff-Kishner reduction & a chemical reaction used to convert the carbonyl group (C=O) of an aldehyde or ketone completely into a…
Correct answer: Alkane- A. Free radical substitution mechanism
- B. Nucleophilic addition mechanism
- C. Electrophilic substitution mechanism
- D. Nucleophilic substitution mechanism
Explanation: Halogenation of alkanes occurs in the presence of light or heat. It involves formation of free radicals and substitution of hydrogen by…
Correct answer: Free radical substitution mechanism- A. Formic acid
- B. Oxalic acid
- C. Acetic acid
- D. Hydrochloric acid
Explanation: Oxidation of ethyne with alcoholic potassium permanganate (KMnO4) converts the triple bond into oxalic acid.
Correct answer: Oxalic acid- A. CO, H₂O, and a catalyst
- B. CO, CH3OH, and a Ni(CO)4 catalyst
- C. CH3COOH and a catalyst
- D. HCN and a catalyst
Explanation: This describes a specific carbonylation reaction. Acetylene reacts with carbon monoxide and an alcohol (methanol, CH3OH) in the presence…
Correct answer: CO, CH3OH, and a Ni(CO)4 catalyst- A. Ethyl & methyl benzene
- B. Iso-Propyl benzene
- C. n-Propylbenzene
- D. Chlorobenzene
Explanation: In the Friedel-Crafts alkylation, the reaction proceeds via a carbocation intermediate.
Correct answer: Iso-Propyl benzene- A. Single
- B. Double
- C. Triple
- D. None
Explanation: Alkynes are unsaturated hydrocarbons that contain a carbon-carbon triple bond (C=C) at the carbon site.
Correct answer: Triple- A. In alkylation, a gaseous byproduct is evolved
- B. In alkylation, a large amount of heat is evolved
- C. In alkylation, polyalkylated products are often formed
- D. Alkylation is very costly
Explanation: Friedel-Crafts alkylation is prone to two major side reactions: carbocation rearrangements and polyalkylation.
Correct answer: In alkylation, polyalkylated products are often formed- A. Bromine water
- B. KMnO4 solution
- C. Tollen's reagent
- D. Chlorine gas
Explanation: 1-Butyne is a terminal alkyne with an acidic hydrogen, while 2-butyne is internal.
Correct answer: Tollen's reagent- A. Pyrrole
- B. Benzene
- C. Toluene
- D. Thiophene
Explanation: When acetylene reacts with H₂S in the presence of hot Al203 cyclization occurs. Sulfur gets incorporated into the ring structure.
Correct answer: Thiophene- A. 1-chloro-2-methylbutane
- B. 2-chloro-2-methylbutane
- C. 2-chloro-3-methylbutane
- D. 1-chloro-3-methylbutane
Explanation: The Wurtz reaction (with Na) couples two alkyl halides, so the product 2,7-dimethyloctane must have come from two molecules of the…
Correct answer: 1-chloro-3-methylbutane- A. propene
- B. but-1-ene
- C. but-2-ene
- D. 2,3-dimethyl-2-butene
Explanation: Ozonolysis cleaves a double bond and replaces it with two carbonyl groups.
Correct answer: 2,3-dimethyl-2-butene- A. Dehydrohalogenation of vic-dihalides
- B. Dehalogenation of tetrahalides
- C. Electrolysis of aqueous solution of potassium salt of unsaturated dicarboxylic acids
- D. Reaction of calcium carbide with water
Explanation: On an industrial scale, ethyne (acetylene) is prepared by reacting calcium carbide with water, which produces ethyne and calcium hydroxide.
Correct answer: Reaction of calcium carbide with water