Hello NEET aspirants. In this article we brought to you the MCQ questions from class 12 chapter named as "Haloalkanes and Haloarenes". Answer key and detailed solutions are also provided in this article so that you don't have any doubts left for any of the questions. Good Luck! 

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Questions

1. Among the following the one that gives positive iodoform test upon reaction with I₂ and NaOH is
a) CH₃CH₂CH(OH)CH₂CH₃
b) C₆H₅CH₂CH₂OH
c) H₃C-CH(CH₃)-CH₂OH
d) PhCHOHCH₃

2. Vicinal and geminal dihalides can be distinguished by:
a) KOH (aq.)
b) KOH (alc.)
c) Zn dust
d) None of these

3. An alkyl halide may be converted into an alcohol by:
a) Addition
b) Substitution
c) Dehydrohalogenation
d) Elimination

4. Dehydrohalogenation in haloalkanes produces:
a) A single bond
b) A double bond
c) A triple bond
d) Fragmentation

5. Chlorination of CS₂ gives:
a) CCl₄
b) CS₂Cl₂
c) CH₄
d) CHCl₃

6. Methylene chloride on hydrolysis yields:
a) HCHO
b) CH₃CHO
c) CHCl₃
d) CH₃COCl

7. The greater the ionic character of the carbon metal bond:
a) The more reactive is the organometallic compound
b) The less reactive is the organometallic compound
c) Both are correct
d) None of the above is correct

8. For the reaction,
C₂H₅OH + HX  C₂H₅X, the order of reactivity is:

a) HI > HCl > HBr
b) HI > HBr > HCl
c) HCl > HBr > HI
d) HBr > HI > HCl

9. The order of reactivities of methyl halides in the formation of Grignard reagent is
a) CH₃I > CH₃Br > CH₃Cl
b) CH₃Cl > CH₃Br > CH₃I
c) CH₃Br > CH₃Cl > CH₃I
d) CH₃Br > CH₃I > CH₃Cl

10. The antiseptic character of iodoform is due to:
a) Its poisonous nature
b) Unpleasant smell
c) Liberation of free iodine
d) None of the above

11. On treating a mixture of two alkyl halides with sodium metal in dry ether, 2-methyl propane was obtained. The alkyl halides are
a) 2-chloropropane and chloromethane
b) 2-chloropropane and chloroethane
c) Chloromethane and chloroethane
d) Chloromethane and 1-chloropropane

12. The IUPAC name of the compound, (CH₃)₂CHCH₂CH₂Br is:
a) 2-methyl-3-bromopropane
b) 1-bromopentane
c) 2-methyl-4-bromobutane
d) 1-bromo-3-methylbutane

13. The given reaction is an example of,
C₂H₅Br + KCN_(aq.) ⟶ C₂H₅CN + KBr
a) Elimination
b) Nucleophilic substitution
c) Electrophilic substitution
d) Redox change

14. Which one of the following compound reacts with chlorobenzene to produce DDT?
a) Acetaldehyde
b) Nitrobenzene
c) m-chloroacetaldehyde
d) Trichloroacetaldehyde

15. Preparation of alkyl halides in laboratory is least preferred by:
a) Halide exchange
b) Direct halogenation of alkanes
c) Treatment of alcohols
d) Addition of hydrogen halides to alkenes

16. Which one of the following pairs is the strongest pesticide?
a) Chloroform and benzene hexachloride
b) DDT and 666
c) 666 and ether
d) isocyanides and alcohol

17. Iodoform gives a precipitate with AgNO₃ on heating but chloroform does not because:
a) Iodoform is ionic
b) Chloroform is covalent
c) C—I bond in iodoform is weak and C—Cl bond in chloroform is strong
d) None of the above

18. Which reagent is useful in increasing the carbon chain of an alkyl halide?
a) HCN
b) KCN
c) NH₄CN
d) AgCN

19. Chloroform on reaction with conc. HNO₃ gives an insecticide and war gas known as:
a) Chloropicrin
b) Nitromethane
c) Picric acid
d) Acetylene

20. Aryl halides are less reactive towards electrophiles than alkyl halides due to:
a) Resonance
b) Stability of carbonium ions
c) High boiling point
d) None of the above

21. Carbon tetrachloride reacts with steam at 500℃ to give:
a) COCl₂
b) CHCl₃
c) Both (a) and (b)
d) None of these

22. Chloroform on reaction with acetone yields:
a) Insecticide
b) Hypnotic agent
c) Analgesic
d) Isocyanide

23. In Wurtz reaction alkyl halide reacts with
a) Sodium in ether
b) Sodium in dry ether
c) Sodium only
d) Alkyl halide in ether

24. When iodoform is heated with silver powder it forms:
a) Acetylene
b) Ethylene
c) Methane
d) Ethane

25. 1,3-dibromopropane reacts with metallic zinc to form:
a) Propene
b) Cyclopropane
c) Propane
d) Hexane

Answers

Explanation

1 (d) For positive iodoform test, alcohol molecule must have

2 (a)

8 (b)
HI reacts with C₂H₅OH even in absence of ZnX₂. Larger is bond length, more is reactivity.

9 (a)
Among alkyl halides, iodides are least stable, hence these form Grignard reagent easily. Hence, the correct order of reactivity in formation of Grignard reagent is CH₃I > CH₃Br > CH₃Cl

10 (c)
The I₂ has antiseptic nature.

11 (a)
This is Wurtz reaction. 2-chloropropane and chloromethane reacts in presence of dry ether t form 2-methyl propane.

13 (b)
Br is replaced by a nucleophileCN^-.

15 (b)
A mixture of halides is formed.

16 (b)
DDT and 666 (C₆H₆Cl₆ or benzene hexachloride) is the pair of strongest pesticides.

17 (c)
Thus, decomposition of CHI₃ occurs.

18 (b)
CH₃X + KCN ⟶ CH₃CN 

19 (a)
CHCl₃ + HNO₃ ⟶ CCl₃∙NO₂ + H₂O∙CCl₃∙NO₂ is called chloropicrin. 

20 (a)
Aryl halides show resonance in their structure. 

21 (a)
CCl₄ + H₂O(v) ⟶ COCl₂ + 2 HCl 

23 (b)
In Wurtz reaction alkyl halide react with sodium in dry ether to produce alkane having double number of carbon atoms as in alkyl halide. 

24 (a)
CH₃I + 6 Ag + I₃HC ⟶ C₂H₂ + 6 AgX 

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