Class 11 • Chemistry • Chapter 9
Hydrocarbons
True & False Quiz
Saturate. Unsaturate. Aromatise.
✓True
✗False
25
Questions
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Ch.9
Chapter
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XI
Class
Why True & False for Hydrocarbons?
How this format sharpens your conceptual clarity
🔵 Hydrocarbons are the simplest organic compounds and the backbone of fuels, plastics, and petrochemicals — alkanes, alkenes, alkynes, and arenes.
✅ T/F tests general formulas, hybridisation, Markovnikov/anti-Markovnikov addition, ozonolysis, and aromaticity (Hückel's rule).
🎯 Markovnikov's rule applies to unsymmetrical alkenes/alkynes with symmetrical reagents (like HX) — in the presence of peroxides, HBr instead follows the anti-Markovnikov (Kharasch) pathway.
📋
Read each statement carefully. Click True or False — instant feedback with explanation appears. Submit anytime; unattempted questions are marked Skipped.
Q 1
All hydrocarbons contain only carbon and hydrogen atoms.
Q 2
Alkanes are saturated hydrocarbons because they contain only single covalent bonds.
Q 3
The general formula of open-chain alkanes is \(C_nH_{2n}\).
Q 4
Alkenes contain at least one carbon-carbon double bond.
Q 5
Ethyne belongs to the alkene family.
Q 6
The carbon atom in methane is \(sp^3\)-hybridised.
Q 7
The bond angle in methane is approximately \(120^\circ\).
Q 8
Alkenes generally undergo addition reactions more readily than alkanes.
Q 9
Bromine water is decolourised by ethene.
Q 10
Methane readily reacts with bromine water at room temperature in the absence of sunlight.
Q 11
Benzene is an aromatic hydrocarbon.
Q 12
All carbon-carbon bonds in benzene have identical lengths.
Q 13
Benzene normally undergoes electrophilic substitution rather than addition reactions.
Q 14
Ethene can be converted into ethane by catalytic hydrogenation.
Q 15
Cold dilute \(KMnO_4\) is used to detect unsaturation in hydrocarbons.
Q 16
Terminal alkynes are more acidic than alkanes.
Q 17
Acetylene gives a precipitate with ammoniacal silver nitrate solution.
Q 18
The molecular formula of benzene is \(C_6H_{12}\).
Q 19
Propene exhibits geometrical isomerism.
Q 20
But-2-ene can exist as cis and trans isomers.
Q 21
The carbon-carbon triple bond is shorter and stronger than the carbon-carbon double bond.
Q 22
Toluene is more reactive than benzene towards electrophilic substitution.
Q 23
Nitrobenzene undergoes electrophilic substitution more readily than benzene.
Q 24
Complete combustion of hydrocarbons produces only carbon dioxide and water.
Q 25
The order of acidity is Alkanes \(>\) Alkenes \(>\) Alkynes.
Key Takeaways — Hydrocarbons
Core facts for CBSE Boards & exams
1
Alkanes (CₙH₂ₙ₊₂, sp³, saturated): undergo free-radical substitution (halogenation) and combustion.
2
Alkenes (CₙH₂ₙ, sp², one C=C): undergo electrophilic addition; Markovnikov's rule — H adds to the carbon already bearing more hydrogens.
3
Alkynes (CₙH₂ₙ₋₂, sp, one C≡C): undergo addition reactions similar to alkenes but can add two molecules of reagent.
4
Ozonolysis cleaves C=C or C≡C bonds at the multiple bond, useful for locating the position of unsaturation.
5
Aromaticity (Hückel's rule): planar, fully conjugated cyclic system with (4n+2) pi electrons, e.g., benzene has 6 pi electrons (n=1).
6
Benzene undergoes electrophilic aromatic substitution (nitration, halogenation, sulphonation, Friedel-Crafts) rather than addition, preserving aromatic stability.
7
Peroxide effect (Kharasch effect): only HBr (not HCl or HI) adds anti-Markovnikov to unsymmetrical alkenes in presence of peroxides.