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NEET Chemistry MCQ
Hydrocarbons Mcq Neet Chemistry
Quiz 11
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Q.1
One mole of an unsaturated hydrocarbon on ozonolysis gives one mole each of CH3CHO, HCHO and OHC-CHO. The hydrocarbon is ..[ PMT kerala 2006]
0%
a) CH3CH2 - C ≡ C - CH3
0%
b) HC ≡ C - CH2CH2CH3
0%
c) CH3CH = CHCH = CH2
0%
d) H2C=C=CHCH2CH3
Explanation
Answer:(c)
Q.2
on Q304) In the followingreaction what is X
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a) CH3CH2OH
0%
b) CH3- O- CH3
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c) CH3CH2CHO
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d) CH2= CHOH
Explanation
X is CH2=CHOH tautomerises to CH3CHO Answer:(d)
Q.3
Which of the following not only decolourises alkaline potassium permaganate but also gives red precipitate with ammoniacal cuprous chloride solution? [ EAMCET 2006]
0%
a) ethane
0%
b) methane
0%
c) ethene
0%
d) acetylene
Explanation
Answer:(d)
Q.4
An unkowncompound A has a molecular formula C4H6, when A is treatedwith an excess of Br2, a new substance B with formula C4H6Br4 is formed. A forms a white precipitate with ammonical silvr nitrate solution. A may be ..[ MPPMT1998]
0%
a) Butyne-1
0%
b) Butyne-2
0%
c) Butene -1
0%
d) Butene-2
Explanation
white precipitate with ammonical silvr nitrate solution indicate, compound A have terminal alyene Also 2 moles of Br2 reacts with C4H6 indicates A is 1-butyne Answer:(a)
Q.5
on Q307) Hydrogenation of the adjoining compound in the presence of poisoned palladium catalyst gives ...[ IIT 2001]
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a) an optically active compound
0%
b) an optically inactive compound
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c) a racemic mixture
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d) a diastereomeric mixture
Explanation
Answer:(b)
Q.6
The class of reactions given by benzeneis
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a) electrophiulic
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b) nucleophilic substitution
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c) electrophilic substitution
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d) nucleophilic addition
Explanation
Answer:(c)
Q.7
The compound X general formula C5H8 reacts with ammonical AgNO3 to give white precipitate and on oxidation with hot alkalin KMnO4 gives the acid, (CH3)2CHCOOH. Therefore, X is ... [ AIIMS 1994]
0%
a) CH2= CHCH = CHCH3
0%
b) CH3(CH2)2C ≡ CH
0%
c) (CH3)2CH - C≡ CH
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d) (CH3)2C =C = CH2
Explanation
White precipitate on reaction with Amonical AgNO3 indicate terminating alkyne Also oxidation it producesacid then option c is correct Answer:(c)
Q.8
The highest boiling point is expected for ...[ IIT 1986]
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a) iso-butane
0%
b) n-octane
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c) 2,2,3,3-tetramethyl butane
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d) n-methyl pentane
Explanation
Boiling point of alkane increases with molar mass. Among isomeric alkanes, branching decreases boiling point. Therefore, n-octane has highest boiling point Answer:(b)
Q.9
The number of geometrical isomers in CH3 - CH = CH - CH2 - CH = CH2 is .... [ DPMT 2007]
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a) two
0%
b) three
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c) four
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d) five
Explanation
Answer:(a)
Q.10
Which of the following deactivates benzene towards further substitution reaction? [ Haryana CEET 1998]
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a) -OR
0%
b) -OH
0%
c) -NHR
0%
d) -COOR
Explanation
-COOR have a strong -R effect, which deactivates benzene ring Answer:(d)
Q.11
The angle strain in cyclobutane is ...[ Karnataka CET 2008]
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a) 19° 22'
0%
b) 9° 44'
0%
c) 24° 44'
0%
d) 29° 16'
Explanation
The angle strain in cyclobutane is 9°44' ( while in cyclopropane it is 24°44') Answer:(b)
Q.12
Which of the following will convert CH≡CH - CH2-CH2CH3 to CH3COCH2CH3? ..[ BHU 2003]
0%
a) H2O/H+
0%
b) H2SO4(conc.)/H3PO4
0%
c) Hg2+/H2SO4
0%
d) K2Cr2O7/KMnO4
Explanation
Answer:(c)
Q.13
A group which deactivates the benzene ring towards electrophilic substitution but which directs the incoming group principally to the o- and p- position is ...[ Pb PMT 1998]
0%
a) -NH2
0%
b) -Cl
0%
c) -NO2
0%
d) -C2H5
Explanation
Cl atom deactivate the benzene due to -I effect but directs the incoming group principaly to the o- and p- position due to its +R effect Answer:(b)
Q.14
Among the three conformations of ethane, the order of stability follows the sequence [ Kerala 2012]
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a) eclipsed > gauche > staggered
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b) eclipsed > staggered > gauche
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c) staggered > gauche > eclipsed
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d) gauche > staggered > eclipsed
Explanation
The eclipsed conformation is least stable because the hydrogens and bonding pairs of electrons on adjacent carbon atoms are as close to one another as possible. This causes maximum repulsion and least stability. Staggered conformation is most stable because of minimum repulsion. Gauche conformation lie between these two in stability. Thus, order of stability is staggered > gauche > eclipsed Answer:(c)
Q.15
Statement: Addition of Br2 to 1-butene gives two optical isomers Statement II: The product contains one asymmetric carbon ...[ IIT 1998]
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a) Statement I is correct Statement II is correct Satement II is a correct explanation of statement I
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b) Statement I is correct statement II is correct statement II is not the correct explanation of statement I
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c) Statement I is correct, statement II is incorrect
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d) Statement I is incorrect statement II is correct
Explanation
CH3 - CH2 - CH = CH2 + Br2 → CH3 - CH2 - CHBr - CH2Br ( has one chiral carbon) Both statemnts are correct and statement II is correct explanation of statement I Answer:(a)
Q.16
Choose the compound which can react with [Ag(NH3)2]+ and on treatment with alk.KMnO433C-COOH ..[ Rajasthan PMT 2002]
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a) CH3CH2CH2-C≡C- CH3
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b) (CH3)2CHCH2 - C ≡CH
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c) (CH3)3C - C ≡ CH
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d) (CH3)3C-C≡C - CH3
Explanation
given that compound reacts with [Ag(NH3)2]+, it must be ≡CH group, onxidation it gives -COOH group. therefor it must contain-C≡ group. Option "c" Answer:(c)
Q.17
he number of stereoisomers obtained by bromination of trans-2-buten is ...[ IIT 2007]
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a) 1
0%
b) 2
0%
c) 3
0%
d) 4
Explanation
Br2 undergo anti-addition on C=C bonds to produce meso isomer Answer:(a)
Q.18
Benzene reacts with methyl chloride in the presence of anhydrous AlCl3 to form ...[ AIMPT 2009]
0%
a) chlorobenzene
0%
b) toluene
0%
c) xylene
0%
d) benzyl chloride
Explanation
Answer:(b)
Q.19
The alkene C6H10 producing OHC(CH2)4CHO onozonolysisis
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a) Cyclohexene
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b) Hexene-1
0%
c) Hexene-3
0%
d) 1-methylcyclohexene-1
Explanation
Since the alkene (C6H10)on ozonolysisgives asingle dialdehyde containing six C-atoms, there fore, thealkene must be cyclohexene Answer:(a)
Q.20
A hydrocarbon of molecular formula, C6H10 reacts with sodamide and the same on ozonolysis followed by hydrogen peroxide oxidation gives two molecules of carboxylic acids, one being optically active. Then the hydrocarbon may be ...[ Kerala PMT 2007]
0%
a) 1-hexyne
0%
b) 2-hexyne
0%
c) 3-hexyne
0%
d) 3-methyl-1-pentyne
Explanation
Answer:(d)
Q.21
The order of activity of the various o and p- director is ... [ DEC 2000]
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a) -O- > -OH > -OCOCH3 > -COCH3
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b) -OH > -O- > -OCOCH3 > -COCH3
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c) -OH > -O- > -COCH3 > -OCOCH3
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d) -O- > -COCH3 > -OCOCH3 > -OH
Explanation
Order of activating group -O- > -NR2 >-OH > -NH2> -OCH3> -NHCOCH3> -CH3 Order of deactivating groups -N+(CH3)3 > -NO2 > -SO3H > -CHO > -COCH3 > -COOH Answer:(a)
Q.22
Anti-Markownikoff's addition is not observed in ... [ CET (J&K) 2012]
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a) 2-butene
0%
b) 1-butene
0%
c) propene
0%
d) 2-pentene
Explanation
Anti-Markownikoff's addition of HBr is observed only with unsymmetrical alkenes (i.e) propene,1-butene,pent-2-ene.As 2-butene is symmetrical so in its case anti-Markownikoff's addition will not be observed. Answer:(a)
Q.23
The addition of Hbr is easiest with ...[ MPPMT 2000]
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a) CH2 = CHCl
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b) ClCH = CHCl
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c) CH3-CH=CH2
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d) (CH3)2C = CH2
Explanation
Due to the presence of two CH3 groups, the double bond in (CH3)2C = CH2 has high electron-density and hence reacts fastest with HBr Answer:(d)
Q.24
The carbon-carbon bond length in benzene is ...[ Karnataka 2009]
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a) same as in C2H4
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b) in between C2H6 and C2H2
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c) in between C2C6 and C2 H
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d) in between C2H4 and C2H2
Explanation
The C - C bond length in benzene (1.39 Å) is in between C2H6 (1.54Å) and C2H4 (1.33Å) Answer:(c)
Q.25
Among the paraffins it is generally found that with an increase in the molecular weight
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a) The freezing point decreases
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b) The boiling point decreases
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c) The boiling point increases
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d) The vapour density decreases
Explanation
Boiling point increases with the increase in molecular weight Answer:(c)
Q.26
Which of the following is the most reactive towards ring nitration? [ DEC 1994]
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a) Benzene
0%
b) Mesitylene
0%
c) Tolune
0%
d) m-Xylene
Explanation
Mesitylene (1, 3, 5-trimethylbenzene) has three, m-xylene (1,3-dimethyl benzene) has two while toluene has only one electron donating CH3 group. Now due to three donating group Mesityleneis more reactive Answer:(d)
Q.27
Which of the following species does not exert a resonance effect? [ Karataka CET 2008]
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a) C6H5OH
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b) C6H5Cl
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c) C6H5NH2
0%
d) C6H5N+H3
Explanation
C6H5N+H3 does not exert a resonance effect Answer:(d)
Q.28
Benzene reacts with CH3Cl in the presence of anhydrous AlCl3 to form ... [ AIPMT 2009]
0%
a) Xylene
0%
b) Toluene
0%
c) Chlorobenzene
0%
d) Benzylchloride
Explanation
It is a alkylation of benzene reaction reaction gives tolune Answer:(b)
Q.29
Nitrobenzene can be prepared from benzene by using a mixture of conc. HNO3 and conc. H2SOIn the mixture, nitric acid acts as ..[ AIPMT 2009] a/an -
0%
a) catalyst
0%
b) reducing agent
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c) acid
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d) base
Explanation
Proton doner is an acid and acceptor is base HNO3 + H2SO4 → H2NO3+ + HSO4- H2NO3+ → NO2+ + H2O From above it is cleared that HNO3 accepts proton hence base Answer:(d)
Q.30
Which of the following reactions is an exampleof nucleophilic substitution reaction ? [ AIPMT 2009]
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a) RX + Mg →RMgX
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b) RX + KOH → ROH + KX
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c) 2RX + 2Na → R – R + 2NaX
0%
d) RX + H2 → RH + HX
Explanation
R – X + KOH → R – OH + KX X– replaced by OH– show nucleophilic substitution reaction Answer:(b)
0 h : 0 m : 1 s
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