Q.1 Which of the following is the correct molecular formula for ethyne?
C2H2
C2H4
C2H6
CH4
Explanation - Ethyne (acetylene) is an alkyne with a triple bond between two carbon atoms, hence formula C2H2.
Correct answer is: C2H2
Q.2 Which type of hydrocarbon contains only single bonds?
Alkene
Alkyne
Alkane
Aromatic
Explanation - Alkanes are saturated hydrocarbons with only single bonds (C-C) between carbon atoms.
Correct answer is: Alkane
Q.3 Benzene is classified as which type of hydrocarbon?
Alkane
Alkene
Alkyne
Aromatic
Explanation - Benzene has a cyclic structure with alternating double bonds, making it aromatic.
Correct answer is: Aromatic
Q.4 Which reaction is typical of alkenes?
Substitution
Addition
Oxidation
Polymerization
Explanation - Alkenes have a C=C double bond, which reacts via addition reactions with halogens or hydrogen.
Correct answer is: Addition
Q.5 What is the IUPAC name of CH3-CH2-CH3?
Propane
Propyne
Propene
Methane
Explanation - The compound has three carbon atoms connected by single bonds, making it propane.
Correct answer is: Propane
Q.6 Which of the following hydrocarbons is unsaturated?
Methane
Ethane
Ethene
Propane
Explanation - Ethene has a C=C double bond, making it unsaturated.
Correct answer is: Ethene
Q.7 The general formula of alkynes is:
CnH2n+2
CnH2n
CnH2n-2
CnHn
Explanation - Alkynes have one triple bond; general formula is CnH2n-2.
Correct answer is: CnH2n-2
Q.8 Which of the following hydrocarbons is aromatic?
Cyclohexane
Benzene
Ethane
Butyne
Explanation - Benzene has a planar cyclic structure with delocalized pi electrons, classifying it as aromatic.
Correct answer is: Benzene
Q.9 Which hydrocarbon can undergo free radical substitution?
Alkane
Alkene
Alkyne
Aromatic
Explanation - Alkanes undergo free radical substitution, e.g., halogenation under UV light.
Correct answer is: Alkane
Q.10 The reaction of ethene with bromine water is an example of:
Substitution
Addition
Elimination
Condensation
Explanation - Ethene reacts with bromine (Br2) via addition across its double bond.
Correct answer is: Addition
Q.11 Which of the following hydrocarbons is gaseous at room temperature?
Methane
Octane
Decane
Hexadecane
Explanation - Methane (CH4) is a small molecule with low boiling point, existing as gas at room temperature.
Correct answer is: Methane
Q.12 The functional group -C≡C- is characteristic of which hydrocarbon?
Alkane
Alkene
Alkyne
Aromatic
Explanation - A triple bond between carbons is the defining feature of alkynes.
Correct answer is: Alkyne
Q.13 Cycloalkanes are:
Unsaturated
Aromatic
Saturated
Polymers
Explanation - Cycloalkanes contain single bonds in a ring structure, so they are saturated.
Correct answer is: Saturated
Q.14 Which hydrocarbon is used as a fuel in lighters?
Butane
Methane
Ethene
Benzene
Explanation - Butane is commonly used in lighter fuel because it is gaseous under pressure and burns easily.
Correct answer is: Butane
Q.15 The IUPAC name of CH≡C-CH3 is:
Propyne
Propene
Propanol
Propanal
Explanation - CH≡C-CH3 is an alkyne with triple bond on the first carbon; name is propyne.
Correct answer is: Propyne
Q.16 Which is the main product when ethyne reacts with hydrogen in the presence of Lindlar’s catalyst?
Ethane
Ethene
Acetylene
Benzene
Explanation - Partial hydrogenation of ethyne using Lindlar’s catalyst produces cis-ethene.
Correct answer is: Ethene
Q.17 Which property increases with an increase in chain length of alkanes?
Boiling point
Volatility
Flammability
Reactivity with halogens
Explanation - Longer alkanes have stronger Van der Waals forces, increasing boiling points.
Correct answer is: Boiling point
Q.18 Which hydrocarbon is a major component of natural gas?
Methane
Ethene
Benzene
Propene
Explanation - Methane constitutes about 70–90% of natural gas.
Correct answer is: Methane
Q.19 What is the product when methane undergoes chlorination in presence of UV light?
CH3Cl
CH2Cl2
CHCl3
All of the above
Explanation - Stepwise chlorination of methane yields CH3Cl, CH2Cl2, CHCl3, and finally CCl4.
Correct answer is: All of the above
Q.20 Which of the following is a straight-chain alkane?
Isobutane
n-Butane
Cyclobutane
Methylpropane
Explanation - n-Butane has four carbon atoms in a straight chain.
Correct answer is: n-Butane
Q.21 Which reaction converts an alkene to an alcohol?
Hydration
Hydrogenation
Halogenation
Combustion
Explanation - Alkenes react with water in presence of acid to form alcohols.
Correct answer is: Hydration
Q.22 Which hydrocarbon contains a benzene ring?
Cyclohexane
Toluene
Butane
Ethene
Explanation - Toluene consists of a methyl group attached to a benzene ring.
Correct answer is: Toluene
Q.23 The homologous series with general formula CnH2n+2 is:
Alkanes
Alkenes
Alkynes
Aromatic hydrocarbons
Explanation - Alkanes are saturated hydrocarbons with general formula CnH2n+2.
Correct answer is: Alkanes
Q.24 Which compound is an isomer of pentane?
Butane
2-Methylbutane
Hexane
Propane
Explanation - 2-Methylbutane has the same molecular formula (C5H12) as pentane but a different structure.
Correct answer is: 2-Methylbutane
Q.25 What type of bond is present between carbon atoms in ethene?
Single
Double
Triple
Ionic
Explanation - Ethene (C2H4) has a carbon-carbon double bond.
Correct answer is: Double