CBSE Class 11 Chemistry Hydrocarbons MCQs Set A

Question. A dibromo derivative of an alkane reacts with sodium metal to form an alicyclic hydrocarbon. The derivative is ______.
(a) 2, 2-dibromobutane
(b) 1, 1-dibromopropane
(c) 1, 4-dibromobutane 
(d) 1, 2-dibromoethane

Answer: c

Question. Among the following compounds the one that is most reactive towards electrophilic nitration is
(a) Toluene
(b) Benzene
(c) Benzoic Acid
(d) Nitrobenzene

Answer: a

Question. A gas decolourised by KMno4 solution but gives no precipitate with ammoniacal cuprous chloride is
(a) Ethene
(b) Propane
(c) Propene
(d) Methane

Answer: a

Question. A gas decolourised by KMnO₄ solution but gives no precipitate with ammoniacal cuprous chloride is
(a) Ethane
(b) Methane
(c) Ethene
(d) Acetylene

Answer: c

Question. When cyclohexane is poured on water, it floats because
(a) Cyclohexane is in boat form
(b) Cyclohexane is in chair form
(c) Cyclohexane is in crown fromorm
(d) Cyclohexane is less dense than water.

Answer: d

Question. Among the three conformations of ethane, the order of stability follows the sequence :
(a) eclipsed > gauche > staggered
(b) eclipsed > staggered > gauche
(c) staggered > gauche > eclipsed
(d) gauche > staggered > eclipsed     

Answer: c

Question. A dibromo derivative of an alkane reacts with sodium metal to form an alicyclic hydrocarbon. The derivative is _______
(a) 1, 4-dibromobutane
(b) 1, 2-dibromoethane
(c) carbon
(d) none of the above

Answer: a

Question. Which branched chain isomer of the hydrocarbon with molecular mass 72u gives only one isomer of mono substituted alkyl halide?
(a) Neopentane
(b) Carbon
(c) Isohexane
(d) Neohexane

Answer: a

Question. Meta-directing and deactivating group in aromatic electrophilic substitution is
(a) – CH₃
(b) – OH
(c) – NO₂
(d) – Cl   

Answer: c

Question. During ozonolysis of CH₂ == CH₂ if hydrolysis is made in absence of Zn dust the products  formed are
(a) HCHO
(b) HCOOH
(c) CH₂OHCH₂OH
(d) CH₃OH   

Answer: b

Question. Hydrocarbon containing following bond is most reactive
(a) C ≡ C
(b) C = C
(c) C – C
(d) All of these 

Answer: c

Question. Which of the following compounds reacts with sodium to liberate hydrogen gas?
(a) Ethane
(b) Propene
(c) Acetylene
(d) Benzene   

Answer: c

Question. Benzene easily shows
(a) ring fission reactions since it is unstable
(b) addition reactions since it is unsaturated
(c) electrophilic substitution reactions due to stable ring and high p electron density
(d) nucleophilic substitution reactions due to stable ring and minimum electron density.   

Answer: c

Question. Which among the following is very strong o-, p-directing group ?
(a) Cl
(b) OR
(c) NH₂
(d) NHR 

Answer: d

Question. Which of the following compounds will not undergo Friedal-Crafts reaction easily?
(a) Nitrobenzene
(b) Toluene
(c) Cumene
(d) Xylene    

Answer: a

Question. The reaction, RC ≡ CR  →H2Lindlar’s catalyst gives the main product as
(a) cis-alkene
(b) trans-alkene
(c) alkane
(d) none of these. 

Answer: a

Question. Which of the following species is most stable?
(a) p-O₂N — C₆H₄ — C⁺H₂
(b) C₆H₅ — C⁺H₂
(c) p-Cl — C₆H₄ — C⁺H₂
(d) p-CH₃O — C₆H₄ — C⁺H₂   

Answer: d

Question. The function of anhydrous AlCl₃ in Friedel–Crafts reaction is
(a) to absorb water
(b) to absorb HCl
(c) to produce attacking electrophile
(d) to produce nucleophile.   

Answer: c

Question. Which one of these is NOT TRUE for benzene?
(a) Heat of hydrogenation of benzene is less than the theoretical value
(b) There are three carbon-carbon single bonds and three carbon-carbon double bonds
(c) It forms only one type of monosubstituted product
(d) The bond angle between carbon-carbon bonds is 120o

Answer: b

Question. The correct order of reactivity towards electrophilic substitution is
(a) phenol > benzene > chlorobenzene > benzoic acid
(b) benzoic acid > chlorobenzene > benzene > phenol
(c) phenol > chlorobenzene > benzene > benzoic acid
(d) benzoic acid > phenol > benzene > chlorobenzene  

Answer: a

Question. HBr reacts with CH₂ = CH – OCH₃ under anhydrous conditions at room temperature to give
(a) CH₃CHO and CH₃Br
(b) BrCH₂CHO and CH₃OH
(c) BrCH₂ – CH₂ – OCH₃
(d) H₃C – CHBr – OCH₃

Answer: d

Question. Which of the following is Baeyer’s reagent?
(a) alkaline KMnO₄
(b) acidic K₂Cr₂O₇
(c) alkaline Na₂Cr₂O₇
(d) MnO₂   

Answer: a