Hydrocarbons Practice Questions - DPP for JEE

 Page 1


1. (d) A doubly bonded carbon atom having an alkyl group is oxidised to
aldehyde which is further oxidised to carboxylic acid.
 
2. (a)
 
Addition of sulphuric acid takes place according to Markownikoff’s
rule. Alkanes do not absorb cold conc. .
3. (c)
Benzene triozonide
4. (c) 
Page 2


1. (d) A doubly bonded carbon atom having an alkyl group is oxidised to
aldehyde which is further oxidised to carboxylic acid.
 
2. (a)
 
Addition of sulphuric acid takes place according to Markownikoff’s
rule. Alkanes do not absorb cold conc. .
3. (c)
Benzene triozonide
4. (c) 
5. (c)
Since two bromine atoms are lost from different carbon atom, the
reaction is known as ß-elimination.
6. (b)    
7. (a) Toluene on oxidation with mild oxidising agent like chromyl
chloride (CrO
2
Cl
2
) gives benzaldehyde.
  
8. (c)
Addition follows Markownikoff’s rule.
9. (c) We know that
?  and 
10. (c) Hydration of alkynes give ketones.
Page 3


1. (d) A doubly bonded carbon atom having an alkyl group is oxidised to
aldehyde which is further oxidised to carboxylic acid.
 
2. (a)
 
Addition of sulphuric acid takes place according to Markownikoff’s
rule. Alkanes do not absorb cold conc. .
3. (c)
Benzene triozonide
4. (c) 
5. (c)
Since two bromine atoms are lost from different carbon atom, the
reaction is known as ß-elimination.
6. (b)    
7. (a) Toluene on oxidation with mild oxidising agent like chromyl
chloride (CrO
2
Cl
2
) gives benzaldehyde.
  
8. (c)
Addition follows Markownikoff’s rule.
9. (c) We know that
?  and 
10. (c) Hydration of alkynes give ketones.
11. (d) Writing the reaction we get
 
So we find  that CH
4
 is produced in this reaction.
12. (d) 
13. (b) –Cl group is o-, p-directing due to +R effect ; however it is
deactivating due to strong –I effect of Cl (difference from other o-,
p-directing groups which are activating). The net result is that
chlorobenzene undergoes o-, p-substitution, but with difficulty.
14. (d) It is a streoselective reaction and in it a trans product is formed.
[It is a reduction. Metal dissolved reduction Na/C
2
H
5
OH reaction is
stereoselective].
15. (d)
16. (a) Acetylene reacts with the other three as:
Page 4


1. (d) A doubly bonded carbon atom having an alkyl group is oxidised to
aldehyde which is further oxidised to carboxylic acid.
 
2. (a)
 
Addition of sulphuric acid takes place according to Markownikoff’s
rule. Alkanes do not absorb cold conc. .
3. (c)
Benzene triozonide
4. (c) 
5. (c)
Since two bromine atoms are lost from different carbon atom, the
reaction is known as ß-elimination.
6. (b)    
7. (a) Toluene on oxidation with mild oxidising agent like chromyl
chloride (CrO
2
Cl
2
) gives benzaldehyde.
  
8. (c)
Addition follows Markownikoff’s rule.
9. (c) We know that
?  and 
10. (c) Hydration of alkynes give ketones.
11. (d) Writing the reaction we get
 
So we find  that CH
4
 is produced in this reaction.
12. (d) 
13. (b) –Cl group is o-, p-directing due to +R effect ; however it is
deactivating due to strong –I effect of Cl (difference from other o-,
p-directing groups which are activating). The net result is that
chlorobenzene undergoes o-, p-substitution, but with difficulty.
14. (d) It is a streoselective reaction and in it a trans product is formed.
[It is a reduction. Metal dissolved reduction Na/C
2
H
5
OH reaction is
stereoselective].
15. (d)
16. (a) Acetylene reacts with the other three as:
17. (c)
(Since tertiary carbocation is more stable)
18. (d) 
19. (c) Ethene is obtained by electrolysis of dipotassium succinate as
follows
Pot. Succinate
Page 5


1. (d) A doubly bonded carbon atom having an alkyl group is oxidised to
aldehyde which is further oxidised to carboxylic acid.
 
2. (a)
 
Addition of sulphuric acid takes place according to Markownikoff’s
rule. Alkanes do not absorb cold conc. .
3. (c)
Benzene triozonide
4. (c) 
5. (c)
Since two bromine atoms are lost from different carbon atom, the
reaction is known as ß-elimination.
6. (b)    
7. (a) Toluene on oxidation with mild oxidising agent like chromyl
chloride (CrO
2
Cl
2
) gives benzaldehyde.
  
8. (c)
Addition follows Markownikoff’s rule.
9. (c) We know that
?  and 
10. (c) Hydration of alkynes give ketones.
11. (d) Writing the reaction we get
 
So we find  that CH
4
 is produced in this reaction.
12. (d) 
13. (b) –Cl group is o-, p-directing due to +R effect ; however it is
deactivating due to strong –I effect of Cl (difference from other o-,
p-directing groups which are activating). The net result is that
chlorobenzene undergoes o-, p-substitution, but with difficulty.
14. (d) It is a streoselective reaction and in it a trans product is formed.
[It is a reduction. Metal dissolved reduction Na/C
2
H
5
OH reaction is
stereoselective].
15. (d)
16. (a) Acetylene reacts with the other three as:
17. (c)
(Since tertiary carbocation is more stable)
18. (d) 
19. (c) Ethene is obtained by electrolysis of dipotassium succinate as
follows
Pot. Succinate
Element % Ratio of atomsSimplest ratio
C 91.3 91.3/12 = 7.61 7.61/7.61 = 1 × 7 =
7
H 8.7 8.7/1= 8.7 8.7/7.61 = 1.14 ×
At anode :
At cathode :
20. (a) The intermediate 2º carbocation shows resonance
 
21. (2) The given molecular formula suggests that the aldehyde formed will
be acetaldehyde hence the alkene  will be
 2CH
3
CHO
22. (7) Sum of masses of C and H = 10.5 + 1.0 = 11.5
% of C = 
% of H =