Here I am giving you point focus NCERT MCQs. Next time, you will get every question here that comes in any NTA exam.
Syllabus
Introduction to Alkanes
1. The general formula of alkanes is:
a) CₙH₂ₙ
b) CₙH₂ₙ₊₂
c) CₙH₂ₙ₋₂
d) CₙH₂ₙ₋₆
2. Alkanes are also known as:
a) Olefins
b) Paraffins
c) Acetylenes
d) Aromatics
3. The term “paraffin” means:
a) Oil forming
b) Little affinity
c) Sweet smell
d) High reactivity
4. Methane is a gas found in:
a) Volcanoes
b) Coal mines and marshy places
c) Ocean beds
d) Desert sand
5. The C-C bond length in alkanes is approximately:
a) 120 pm
b) 134 pm
c) 154 pm
d) 140 pm
6. The C-H bond length in alkanes is approximately:
a) 112 pm
b) 120 pm
c) 154 pm
d) 100 pm
7. The H-C-H bond angle in methane is:
a) 90°
b) 109.5°
c) 120°
d) 180°
8. Methane has which type of hybridization?
a) sp
b) sp²
c) sp³
d) sp³d
9. Which of the following is the first member of alkane family?
a) Ethane
b) Propane
c) Methane
d) Butane
10. The general formula of alkyl group is:
a) CₙH₂ₙ
b) CₙH₂ₙ₊₁
c) CₙH₂ₙ₋₁
d) CₙH₂ₙ₊₂
11. A carbon atom attached to only one other carbon atom is called:
a) Primary
b) Secondary
c) Tertiary
d) Quaternary
12. The number of chain isomers of C₄H₁₀ is:
a) 1
b) 2
c) 3
d) 4
13. The IUPAC name of isobutane is:
a) Butane
b) 2-Methylpropane
c) 2-Methylbutane
d) Propane
14. Which of the following has the highest boiling point?
a) n-Pentane
b) Isopentane
c) Neopentane
d) All equal
15. The number of structural isomers of C₅H₁₂ is:
a) 2
b) 3
c) 4
d) 5
16. A quaternary carbon is attached to how many other carbon atoms?
a) 1
b) 2
c) 3
d) 4
17. Terminal carbon atoms in an alkane are always:
a) Primary
b) Secondary
c) Tertiary
d) Quaternary
18. Which of the following is a chain isomer of pentane?
a) 2-Methylbutane
b) 2,2-Dimethylpropane
c) Both (a) and (b)
d) Cyclopentane
19. The correct IUPAC name of CH₃–CH(CH₃)–CH₂–CH₃ is:
a) Pentane
b) 2-Methylbutane
c) 3-Methylbutane
d) Isopentane
20. The molecular formula of hexane is:
a) C₅H₁₂
b) C₆H₁₄
c) C₆H₁₂
d) C₇H₁₆
Preparation of Alkanes
21. Hydrogenation of ethene gives:
a) Ethyne
b) Ethane
c) Methane
d) Propane
22. Which catalyst is used for hydrogenation of alkenes at room temperature?
a) Ni
b) Pt or Pd
c) Fe
d) Cu
23. Hydrogenation of propyne with excess H₂ in presence of Ni gives:
a) Propene
b) Propane
c) Propyne
d) Cyclopropane
24. Reduction of chloromethane with Zn + dilute HCl gives:
a) Methane
b) Ethane
c) Chloroethane
d) Methanol
25. Wurtz reaction is used to prepare alkanes containing:
a) Odd number of carbon atoms
b) Even number of carbon atoms
c) Both odd and even
d) Only methane
26. Wurtz reaction requires:
a) Aqueous medium
b) Dry ether
c) Alcohol
d) Acetone
27. 2CH₃Br + 2Na → C₂H₆ + 2NaBr is an example of:
a) Decarboxylation
b) Wurtz reaction
c) Kolbe’s reaction
d) Hydrogenation
28. The product of Wurtz reaction of a mixture of CH₃Br and C₂H₅Br is:
a) Only ethane
b) Only butane
c) Ethane + butane + propane
d) Only propane
29. Which alkane cannot be prepared by Wurtz reaction?
a) Methane
b) Ethane
c) Butane
d) Hexane
30. Decarboxylation of sodium ethanoate with soda lime gives:
a) Ethane
b) Methane
c) Ethene
d) Ethyne
31. Soda lime is a mixture of:
a) NaOH + CaO
b) NaOH + Ca(OH)₂
c) Na₂CO₃ + CaO
d) NaHCO₃ + CaO
32. Which acid is required to prepare propane by decarboxylation?
a) Ethanoic acid
b) Propanoic acid
c) Butanoic acid
d) Pentanoic acid
33. Decarboxylation results in:
a) Increase in carbon chain length by one
b) Decrease in carbon chain length by one
c) No change in chain length
d) Formation of double bond
34. Kolbe’s electrolytic method gives alkane at:
a) Cathode
b) Anode
c) Both electrodes
d) In solution
35. Electrolysis of sodium acetate gives:
a) Methane
b) Ethane
c) Propane
d) Butane
36. Which alkane cannot be prepared by Kolbe’s method?
a) Methane
b) Ethane
c) Butane
d) Hexane
37. The intermediate in Kolbe’s reaction is:
a) Carbocation
b) Carbanion
c) Free radical
d) Carbene
38. Which gas is evolved at the anode during Kolbe’s electrolysis of sodium acetate?
a) H₂
b) O₂
c) CO₂
d) CH₄
39. Hydrogenation of alkenes is an example of:
a) Substitution reaction
b) Addition reaction
c) Elimination reaction
d) Rearrangement
40. Which of the following is not a method for preparation of alkanes?
a) Hydrogenation of alkenes
b) Reduction of alkyl halides
c) Dehydration of alcohols
d) Decarboxylation of carboxylic acids
Conformation of Alkanes
41. Conformers are interconvertible by:
a) Breaking of bonds
b) Rotation around C-C single bond
c) Change in bond angles
d) Change in hybridisation
42. The most stable conformation of ethane is:
a) Eclipsed
b) Staggered
c) Skew
d) Gauche
43. In staggered conformation of ethane, the hydrogen atoms are:
a) As close as possible
b) As far apart as possible
c) Exactly overlapping
d) Randomly arranged
44. The energy barrier between staggered and eclipsed conformation of ethane is about:
a) 1.25 kJ/mol
b) 12.5 kJ/mol
c) 125 kJ/mol
d) 0 kJ/mol
45. Torsional strain is maximum in:
a) Staggered conformation
b) Eclipsed conformation
c) Anti conformation
d) Gauche conformation
46. In Newman projection, the front carbon is represented by:
a) A circle
b) A point
c) A triangle
d) A square
47. In Sawhorse projection, the C-C bond is drawn as:
a) A point
b) A longer straight line
c) A circle
d) A curved line
48. The dihedral angle in eclipsed conformation of ethane is:
a) 0°
b) 60°
c) 120°
d) 180°
49. The dihedral angle in staggered conformation of ethane is:
a) 0°
b) 60°
c) 120°
d) 180°
50. Why can’t different conformations of ethane be isolated at room temperature?
a) They are identical
b) Energy barrier is very low (12.5 kJ/mol)
c) They are ionic
d) They are unstable
Answer Key
| Q. | Ans | Q. | Ans| Q. | Ans| Q. | Ans| Q. | Ans |
|——|—–|——|—–|——|—–|——|—–|——|—–|
| 1 | b | 11 | a | 21 | b | 31 | a | 41 | b |
| 2 | b | 12 | b | 22 | b | 32 | c | 42 | b |
| 3 | b | 13 | b | 23 | b | 33 | b | 43 | b |
| 4 | b | 14 | a | 24 | a | 34 | b | 44 | b |
| 5 | c | 15 | b | 25 | b | 35 | b | 45 | b |
| 6 | a | 16 | d | 26 | b | 36 | a | 46 | b |
| 7 | b | 17 | a | 27 | b | 37 | c | 47 | b |
| 8 | c | 18 | c | 28 | c | 38 | c | 48 | a |
| 9 | c | 19 | b | 29 | a | 39 | b | 49 | b |
| 10 | b | 20 | b | 30 | b | 40 | c | 50 | b |
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