Q.1 Which of the following is a structural isomer of butane (C4H10)?
1-Butene
2-Methylpropane
Butanol
Ethane
Explanation - Butane (C4H10) has two structural isomers: n-butane and 2-methylpropane. Structural isomers have the same molecular formula but different connectivity.
Correct answer is: 2-Methylpropane
Q.2 Which functional group is present in alcohols?
-COOH
-OH
-CHO
-NH2
Explanation - Alcohols are characterized by the hydroxyl functional group (-OH) attached to a carbon atom.
Correct answer is: -OH
Q.3 What is the hybridization of carbon in methane (CH4)?
sp
sp2
sp3
dsp3
Explanation - In methane, the carbon forms four sigma bonds with hydrogen, resulting in sp3 hybridization.
Correct answer is: sp3
Q.4 Which of the following compounds is aromatic?
Cyclohexane
Benzene
Cyclopentane
Ethene
Explanation - Benzene is aromatic because it is cyclic, planar, conjugated, and follows Huckel's rule (4n+2 π electrons).
Correct answer is: Benzene
Q.5 Which reagent is commonly used for halogenation of alkanes?
Br2/UV light
H2SO4
NaOH
KMnO4
Explanation - Alkanes undergo free radical substitution with bromine in the presence of UV light to form haloalkanes.
Correct answer is: Br2/UV light
Q.6 Which type of isomerism arises due to restricted rotation around a double bond?
Chain isomerism
Geometrical isomerism
Functional isomerism
Tautomerism
Explanation - Geometrical (cis-trans) isomerism occurs due to restricted rotation around double bonds.
Correct answer is: Geometrical isomerism
Q.7 Which of the following is a nucleophile?
H+
OH-
Cl2
Br2
Explanation - Nucleophiles are electron-rich species that donate electrons; OH- has a lone pair and acts as a nucleophile.
Correct answer is: OH-
Q.8 Mark the correct IUPAC name of CH3-CH2-CH2-OH.
Propanol
Propan-1-ol
Methanol
Ethanol
Explanation - The hydroxyl group is on the first carbon, so the correct IUPAC name is propan-1-ol.
Correct answer is: Propan-1-ol
Q.9 Which of the following is an electrophile?
CH3-
Br-
Cl+
NH3
Explanation - Electrophiles are electron-deficient species that accept electrons; Cl+ is electron-deficient.
Correct answer is: Cl+
Q.10 Which reaction converts an alkene into an alcohol?
Hydration
Dehydration
Halogenation
Oxidation
Explanation - Hydration of an alkene in the presence of acid adds water across the double bond to form an alcohol.
Correct answer is: Hydration
Q.11 Which of the following represents tautomerism?
CH3CH2OH ⇌ CH3CHO
CH4 ⇌ C2H6
C2H4 ⇌ C2H6
CH3Cl ⇌ CH2Cl2
Explanation - Tautomerism is the interconversion of structural isomers, typically keto-enol forms. Ethanol and acetaldehyde show this behavior under certain conditions.
Correct answer is: CH3CH2OH ⇌ CH3CHO
Q.12 Which type of reaction involves breaking of σ bonds and formation of π bonds?
Addition
Elimination
Substitution
Oxidation
Explanation - Elimination reactions remove atoms/groups and form a double bond (π bond) in place of σ bonds.
Correct answer is: Elimination
Q.13 Which of the following compounds is an alkyne?
Ethene
Ethyne
Ethane
Propanol
Explanation - Alkynes are hydrocarbons containing at least one triple bond. Ethyne (C2H2) has a triple bond.
Correct answer is: Ethyne
Q.14 Which reagent converts alcohols into alkyl halides?
PCl5
H2SO4
KMnO4
NaOH
Explanation - Phosphorus pentachloride (PCl5) converts alcohols into alkyl chlorides via substitution.
Correct answer is: PCl5
Q.15 Which of the following is a primary alcohol?
CH3CH2CH2OH
(CH3)2CHOH
CH3OH
CH3CH2OH
Explanation - Primary alcohols have the hydroxyl group attached to a carbon bonded to only one other carbon.
Correct answer is: CH3CH2OH
Q.16 What type of hybridization is present in sp2 carbon?
Linear
Trigonal planar
Tetrahedral
Bent
Explanation - sp2 hybridized carbon has three sigma bonds and one unhybridized p orbital, forming a trigonal planar geometry.
Correct answer is: Trigonal planar
Q.17 Which of the following compounds shows optical isomerism?
CH3CHClCH3
CH3CH2CH3
C6H6
CH3OH
Explanation - Optical isomerism occurs when a molecule has a chiral center (carbon with four different groups). CH3CHClCH3 has such a carbon.
Correct answer is: CH3CHClCH3
Q.18 Which of the following is a secondary alcohol?
CH3CH2OH
(CH3)2CHOH
CH3OH
CH3CH2CH2OH
Explanation - Secondary alcohols have the -OH group attached to a carbon bonded to two other carbons.
Correct answer is: (CH3)2CHOH
Q.19 Which of the following compounds undergoes free radical substitution?
Alkane
Alkene
Alcohol
Carboxylic acid
Explanation - Alkanes react with halogens in the presence of UV light via a free radical substitution mechanism.
Correct answer is: Alkane
Q.20 Which of the following is a saturated hydrocarbon?
Ethane
Ethene
Ethyne
Benzene
Explanation - Saturated hydrocarbons contain only single bonds (alkanes). Ethane (C2H6) is an alkane.
Correct answer is: Ethane
Q.21 Which of the following is the correct IUPAC name for CH3-CH2-CHO?
Propanal
Propanone
Propanol
Acetone
Explanation - The compound has an aldehyde group (-CHO) on the first carbon; its IUPAC name is propanal.
Correct answer is: Propanal
Q.22 Which of the following is a common test for unsaturation in organic compounds?
Bromine water
Tollen's test
Fehling's solution
Litmus test
Explanation - Bromine water decolorizes in the presence of alkenes or alkynes due to addition reaction, indicating unsaturation.
Correct answer is: Bromine water
Q.23 Which of the following compounds is a carboxylic acid?
CH3COOH
CH3CH2OH
CH3CHO
CH4
Explanation - Carboxylic acids have the -COOH functional group. CH3COOH is acetic acid, a carboxylic acid.
Correct answer is: CH3COOH
Q.24 Which of the following statements is true about isomerism?
Isomers have different molecular formulas
Isomers have the same molecular formula but different structures
Isomers have identical properties
Isomers cannot be separated
Explanation - Isomers are compounds with the same molecular formula but different arrangements of atoms.
Correct answer is: Isomers have the same molecular formula but different structures