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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- A. Aqueous KMnO4 or K2Cr2O7
- B. Cold dilute alkaline KMnO4 or K2Cr2O7
- C. Alcoholic KMnO4 or K2Cr2O7
- D. Acidified KMnO4 or K2Cr2O7
Explanation: Alkyl benzenes are oxidized to benzoic acid by nascent oxygen, which is produced by reacting acidified KMnO4 or K2Cr2O7 with the alkyl…
Correct answer: Acidified KMnO4 or K2Cr2O7- A. Ethyl benzene
- B. Benzoyl halide
- C. Aniline
- D. Benzophenone
Explanation: When Ethyl benzene is treated with acidified potassium dichromate, the side chain (ethyl group) is oxidized to a carboxylic acid group…
Correct answer: Ethyl benzene- A. C6H5CH3
- B. C6H5CH2CH2CH3
- C. C6H5CH2CH3
- D. All of these
Explanation: When an alkyl group attached to a benzene ring is oxidized by acidified K2Cr2O7, it forms benzoic acid.
Correct answer: All of these- A. Phenol
- B. Benzaldehyde
- C. Benzyl alcohol
- D. Benzoic acid
Explanation: When toluene is oxidized by acidified KMnO4, it undergoes a series of reactions resulting in the formation of benzoic acid.
Correct answer: Benzoic acid- A. Benzene
- B. Benzoic acid
- C. Nitrobenzene
- D. Ethyl benzene
Explanation: Ethyl benzene is the most reactive compound among the options because the ethyl group is an ortho, para directing group that activates the…
Correct answer: Ethyl benzene- A. -NH2
- B. -CHO
- C. -OR
- D. -OH
Explanation: The correct answer is -CHO because it is a meta directing group that deactivates the benzene ring by withdrawing electrons through…
Correct answer: -CHO- A. Benzene
- B. Chlorobenzene
- C. Chloronitrobenzene
- D. 2-Chloronitrobenzene
Explanation: The reaction involves chlorination with CI2/FeCI3 leading to the formation of chlorobenzene, which further reacts with HNO3+H2 SO4 to give…
Correct answer: 2-Chloronitrobenzene- A. To break up the C - H bonds in methane
- B. To break up the chlorine molecules into free radicals
- C. To heat up the mixture
- D. To break up the chlorine molecules into ions
Explanation: Sunlight provides the energy required to break the relatively weak chlorine-chlorine bond, leading to the formation of chlorine radicals.
Correct answer: To break up the chlorine molecules into free radicals- A. Methanol
- B. Ethanol
- C. Carbon dioxide and water
- D. Methanoic acid
Explanation: Option C is correct.When methane is burnt in the presence of a metallic catalyst (Cu), at high temperature (400°C) and pressure (200 atm)…
Correct answer: Carbon dioxide and water- A. CI-CI ---->2Cl
- B. CH3 + Cl2 -----> CI + CH3-CI
- C. CH3+ HCl ----->H'+ H3C-Cl
- D. All of these
Explanation: Option B is correct.The propagation step in the chlorination of methane is the step where a free radical reacts with a reactant molecule…
Correct answer: CH3 + Cl2 -----> CI + CH3-CI- A. It removes water
- B. It form stable complex with benzene
- C. It is protonating nitric acid
- D. It acts as a solvent
Explanation: The correct answer is Option C: It is protonating nitric acid. Concentrated sulfuric acid plays a crucial role in protonating nitric acid…
Correct answer: It is protonating nitric acid- A. It takes place in the presence of less polar solvent (like alcohol)
- B. It takes place at high temperature
- C. It requires a strong nucleophile (base)
- D. It takes place at low temperature
Explanation: Option D is correct.β-elimination reactions are typically favored at higher temperatures, as lower temperatures are more conducive to…
Correct answer: It takes place at low temperature- A. H3PO4
- B. Conc. H2SO4
- C. Al2O3
- D. All are dehydrating agents
Explanation: Option D is correct as all of the given options can act as dehydrating agents.
Correct answer: All are dehydrating agents- A. 1o > alcohol 2o > alcohol 3o alcohol
- B. 3o alcohol > 2o alcohol > 1o alcohol
- C. 2o alcohol > 1o alcohol > 3o alcohol
- D. 3o alcohol > 1o alcohol > 2o alcohol
Explanation: The correct order of ease of dehydration of alcohols is tertiary alcohol > secondary alcohol > primary alcohol.
Correct answer: 3o alcohol > 2o alcohol > 1o alcohol- A. Baeyer's test
- B. Br2(CCl4)
- C. Cl2(CCI4)
- D. Tollen's test
Explanation: Tollen's reagent shows no reaction with either alkenes or alkanes. It is specifically used to differentiate between aldehydes and other…
Correct answer: Tollen's test- A. 1-Pentene
- B. 1-Butene
- C. 1-Hexene
- D. 2-Butene
Explanation: Markownikov's rule states that in the addition of an unsymmetrical reagent to an unsymmetrical alkene, the negative part of the adding…
Correct answer: 2-Butene397. Alkanes are used as fuels. We burn them for many reasons. Which of the following is not its use?
- A. They are used to generate electricity in power stations
- B. They are used to heat our homes and cook our food
- C. For manufacturing a fertilizer
- D. They are used to provide electricity for galvanic cell
Explanation: Option D is correct. A Galvanic cell does not use energy released from the combustion of alkanes.
Correct answer: They are used to provide electricity for galvanic cell- A. It has a low boiling point
- B. Its enthalpy change formation (∆H) is positive
- C. It is susceptible to attack by nucleophilic reagent
- D. It tends to undergo electrophilic substitution rather addition reaction
Explanation: The stability associated with the delocalized pi-electron system in benzene makes it less prone to addition reactions and more prone to…
Correct answer: It tends to undergo electrophilic substitution rather addition reaction- A. Benzoic acid
- B. Benzene
- C. Phenol
- D. Chlorobenzene
Explanation: The hydroxyl group (−OH) in phenol is a strong activating group that enhances the reactivity of the aromatic ring towards electrophilic…
Correct answer: Phenol- A. Benzyl chloride
- B. Benzotrichloride
- C. Benzoyl chloride
- D. Benzal chloride
Explanation: When toluene reacts with chlorine in the presence of sunlight, the ultimate product formed is Benzotrichloride.
Correct answer: Benzotrichloride