What mass of calcium carbide is needed to produce 0.5 mol of ethyne by reaction with water (Ca = 40, C = 12)?
Correct answer C. 32 g
Topic / 36 questions
Chemistry of Hydrocarbons MCQs
Chemistry of Hydrocarbons MCQs are multiple-choice questions on alkanes, alkenes, alkynes and benzene, covering naming, structure, preparation and characteristic reactions. They follow the MDCAT chemistry curriculum, and every question on MCQs360 shows its correct answer instantly so you can check mechanisms, products and simple calculations quickly.
- Gases 40
- Liquids 40
- Solids 40
- Chemical Equilibrium 40
- Reaction Kinetics 40
- Thermochemistry and Energetics 40
- Electrochemistry 40
- Fundamental Concepts of Chemistry 40
- Atomic Structure 39
- Chemical Bonding 39
- Alcohols and Phenols 38
- Industrial Chemistry 37
- Aldehydes and Ketones 37
- Alkyl Halides 37
- s- and p-Block Elements 37
- Chemistry of Hydrocarbons 36
- Fundamental Principles of Organic Chemistry 36
- Carboxylic Acids 36
- Transition Elements 35
- Macromolecules 35
In the free radical chlorination of methane, the initiation step involves ____.
Correct answer A. homolytic fission of Cl₂ by UV light
Which of these is a termination step in the chlorination of methane?
Correct answer C. CH₃• + Cl• → CH₃Cl
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How many structurally different monochloro products can be formed by free radical chlorination of 2-methylbutane?
Correct answer D. 4
Heating bromoethane with alcoholic KOH to form ethene is an example of ____.
Correct answer B. dehydrohalogenation
Benzene prefers substitution rather than addition reactions because ____.
Correct answer C. substitution keeps the delocalised aromatic π system intact
What electrophile attacks the benzene ring during nitration with a mixture of concentrated HNO₃ and H₂SO₄?
Correct answer D. NO₂⁺
Which catalyst is used in the Friedel-Crafts alkylation of benzene with chloromethane?
Correct answer B. Anhydrous AlCl₃
Which substituent on a benzene ring directs an incoming electrophile to the meta position?
Correct answer C. −NO₂
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Which compound gives a white precipitate with ammoniacal silver nitrate?
Correct answer D. Propyne
Hydration of ethyne using dilute H₂SO₄ and HgSO₄ gives ____.
Correct answer D. ethanal
Which substituent on a benzene ring is deactivating but ortho/para-directing?
Correct answer D. –Cl
What is the main product when ethyne reacts with excess hydrogen bromide?
Correct answer A. 1,1-Dibromoethane
What volume of hydrogen at STP is needed to convert 2.6 g of ethyne completely into ethane (C = 12, H = 1, molar volume = 22.4 dm³)?
Correct answer C. 4.48 dm³
What is the product when ethyne is passed into dilute sulphuric acid containing mercury(II) sulphate?
Correct answer B. Ethanal
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What volume of ethyne at STP is produced when 6.4 g of calcium carbide reacts with excess water (Ca = 40, C = 12, molar volume = 22.4 dm³)?
Correct answer C. 2.24 dm³
Ethyne reacts with sodium metal to release hydrogen because ____.
Correct answer D. its hydrogen atoms are weakly acidic, as the sp-hybridised carbon has 50% s character
What is the IUPAC name of CH₃C≡CCH₃?
Correct answer A. But-2-yne
What is the major product of the nitration of nitrobenzene?
Correct answer C. 1,3-Dinitrobenzene
Ethene is more reactive than ethane mainly because ____.
Correct answer B. its π bond is weaker than a σ bond and its electrons are exposed to electrophiles
About Chemistry of Hydrocarbons MCQs
Aliphatic hydrocarbon questions cover IUPAC naming, free radical substitution of methane and ethane with its initiation, propagation and termination steps, the planar shape of ethene, preparation of alkenes by elimination and addition reactions of alkenes and alkynes. Alkyne questions include their acidity, hydrogenation, hydrohalogenation and hydration, and some combustion and hydrogenation volume calculations at STP. Aromatic questions focus on benzene: its delocalised structure, resonance, why it prefers substitution to addition, and electrophilic substitution reactions such as nitration, sulphonation, halogenation and Friedel–Crafts reactions with their catalysts. You will also predict the orienting and activating or deactivating effect of substituents on the benzene ring.
Key facts to remember
- Alkanes react with chlorine in sunlight by free radical substitution; the initiation step is homolytic fission of Cl₂ into chlorine radicals.
- Ethene is planar, its carbons are sp² hybridised with bond angles of about 120°, and its C=C bond consists of one σ and one π bond.
- Benzene has six delocalised π electrons and all its C–C bonds are equal in length, so it prefers substitution reactions that keep its aromatic stability.
- Nitration of benzene uses concentrated HNO₃ and H₂SO₄ to generate the nitronium ion, NO₂⁺; bromination needs a FeBr₃ (or iron) catalyst.
- –OH, –NH₂ and –CH₃ are activating and ortho/para-directing, –NO₂, –CHO, –COOH and –CN are deactivating and meta-directing, and halogens are deactivating but ortho/para-directing.
- Hydration of ethyne with dilute H₂SO₄ and HgSO₄ gives ethanal.
Exams that include Chemistry of Hydrocarbons MCQs
Pakistan
- MDCAT
- ECAT
- NUMS
- AKU
- FSc boards
India
- NEET
- JEE Main
Bangladesh
- HSC
- Medical Admission Test
How to prepare for Chemistry of Hydrocarbons MCQs
- Learn the three steps of free radical substitution and be able to spot which equation is initiation, propagation or termination.
- Make a table of benzene substitution reactions with reagent, catalyst, electrophile and product.
- Memorise substituent effects in three groups: activating o/p, deactivating meta and halogens.
- Apply Markovnikov's rule when adding HX to unsymmetrical alkenes and alkynes.
Frequently asked questions
What does the MDCAT syllabus include in Chemistry of Hydrocarbons?
The PMDC MDCAT curriculum covers naming and free radical substitution of alkanes, naming, shape, reactivity and preparation of alkenes, benzene's structure and electrophilic substitution, the effect of substituents, alkyne naming, preparation, acidity and addition reactions, and substitution versus addition.
Which exams ask Hydrocarbons MCQs?
Hydrocarbons are tested in MDCAT, ECAT, NUMS and AKU entry tests and FSc board papers in Pakistan, in NEET and JEE Main in India, and in HSC and medical admission tests in Bangladesh.
Why does benzene undergo substitution rather than addition?
Benzene's six π electrons are delocalised around the ring, giving it extra stability. Addition would destroy this delocalised system, while substitution replaces a hydrogen atom and keeps the aromatic ring intact, so substitution is energetically favoured.
Last reviewed October 2026