Organic Chemistry Basics MCQs – Some Basic Principles Class 11
Organic Chemistry Basics MCQs – Some Basic Principles (Class 11 Chemistry)
Course: CBSE Class 11 Chemistry – MCQs with Answers and Explanations
Section: Organic Chemistry – MCQ Titles
The following 50 Multiple Choice Questions (MCQs) are strictly based on the NCERT chapter “Some Basic Principles and Techniques of Organic Chemistry”. The questions are arranged section-wise to ensure full syllabus coverage and are supported with clear, concept-clearing explanations, making them ideal for CBSE Class 11 board exam preparation.
Section A: Introduction to Organic Chemistry
1. Organic chemistry is the study of compounds mainly containing
A. nitrogen
B. carbon
C. oxygen
D. sulphur
Answer: B
Explanation: Organic chemistry deals primarily with carbon compounds, especially hydrocarbons and their derivatives.
2. Which property of carbon leads to the formation of a large number of compounds?
A. High electronegativity
B. Catenation
C. Large atomic size
D. Low ionisation energy
Answer: B
Explanation: Catenation is the ability of carbon to form long chains and rings by bonding with itself.
3. Which of the following is NOT an organic compound?
A. Methane
B. Ethanol
C. Carbon dioxide
D. Acetic acid
Answer: C
Explanation: CO₂ is considered inorganic despite containing carbon.
Section B: Hybridisation and Shapes in Organic Molecules
4. Hybridisation of carbon in methane (CH₄) is
A. sp
B. sp²
C. sp³
D. dsp²
Answer: C
Explanation: Carbon forms four equivalent sp³ hybrid orbitals in methane.
5. Shape of ethene (C₂H₄) molecule is
A. tetrahedral
B. linear
C. trigonal planar
D. pyramidal
Answer: C
Explanation: sp² hybridisation gives trigonal planar geometry.
6. Carbon forms four covalent bonds because it has
A. four electrons
B. four valence electrons
C. four shells
D. zero charge
Answer: B
Explanation: Carbon has four valence electrons and completes its octet by sharing.
Section C: Structural Representations of Organic Compounds
7. The simplest representation showing only atoms and bonds is called
A. condensed formula
B. structural formula
C. skeletal formula
D. molecular formula
Answer: B
Explanation: Structural formula shows how atoms are connected.
8. Skeletal formula omits
A. carbon atoms
B. hydrogen atoms attached to carbon
C. heteroatoms
D. multiple bonds
Answer: B
Explanation: In skeletal formula, hydrogens attached to carbon are not shown.
9. Molecular formula of ethane is
A. C₂H₄
B. C₂H₆
C. C₃H₈
D. CH₄
Answer: B
Explanation: Ethane contains two carbon and six hydrogen atoms.
Section D: Classification of Organic Compounds
10. Organic compounds containing only carbon and hydrogen are called
A. alcohols
B. hydrocarbons
C. ketones
D. aldehydes
Answer: B
Explanation: Hydrocarbons consist solely of carbon and hydrogen.
11. Alkanes are
A. unsaturated hydrocarbons
B. aromatic compounds
C. saturated hydrocarbons
D. cyclic hydrocarbons
Answer: C
Explanation: Alkanes contain only single bonds.
12. Which of the following is an unsaturated hydrocarbon?
A. Ethane
B. Propane
C. Ethene
D. Methane
Answer: C
Explanation: Ethene contains a C=C double bond.
Section E: Homologous Series
13. Members of a homologous series differ by
A. CH₂ group
B. H₂ group
C. C₂H₄ group
D. CO group
Answer: A
Explanation: Successive members differ by one –CH₂– unit.
14. Homologous series have the same
A. molecular mass
B. physical properties
C. functional group
D. number of carbon atoms
Answer: C
Explanation: Same functional group gives similar chemical properties.
Section F: Functional Groups
15. Functional group of alcohols is
A. –COOH
B. –CHO
C. –OH
D. –CO–
Answer: C
Explanation: Alcohols contain hydroxyl (–OH) group.
16. Which functional group is present in aldehydes?
A. –COOH
B. –CO–
C. –CHO
D. –OH
Answer: C
Explanation: Aldehydes contain the –CHO group.
17. Carboxylic acids contain
A. –CO–
B. –COOH
C. –OH
D. –CHO
Answer: B
Explanation: –COOH is the carboxyl group.
Section G: Nomenclature of Organic Compounds
18. IUPAC name of CH₃–CH₂–OH is
A. methanol
B. ethanol
C. propanol
D. ethanal
Answer: B
Explanation: Two-carbon alcohol is named ethanol.
19. The longest carbon chain determines
A. suffix
B. prefix
C. root word
D. functional group
Answer: C
Explanation: Root word is based on number of carbon atoms.
20. Which suffix is used for aldehydes?
A. –ol
B. –one
C. –oic acid
D. –al
Answer: D
Explanation: Aldehydes end with –al.
Section H: Isomerism
21. Compounds having same molecular formula but different structures are called
A. isotopes
B. isomers
C. homologues
D. polymers
Answer: B
Explanation: Structural difference leads to isomerism.
22. Which type of isomerism is shown by butane?
A. position isomerism
B. functional isomerism
C. chain isomerism
D. geometrical isomerism
Answer: C
Explanation: Butane has straight and branched chains.
23. Functional isomers have different
A. molecular formula
B. physical state
C. functional groups
D. number of carbon atoms
Answer: C
Explanation: Same formula but different functional groups.
Section I: Electronic Effects
24. Inductive effect is
A. temporary
B. permanent
C. due to resonance
D. due to free radicals
Answer: B
Explanation: Inductive effect is permanent and transmitted through sigma bonds.
25. Electron withdrawing groups show
A. +I effect
B. −I effect
C. +R effect
D. hyperconjugation
Answer: B
Explanation: They pull electron density away.
26. Which group shows +I effect?
A. –NO₂
B. –CN
C. –CH₃
D. –COOH
Answer: C
Explanation: Alkyl groups donate electrons.
Section J: Reaction Intermediates
27. A carbocation is
A. negatively charged carbon
B. neutral carbon
C. positively charged carbon
D. radical carbon
Answer: C
Explanation: Carbocations have a positive charge on carbon.
28. Stability of carbocations increases in the order
A. primary < secondary < tertiary
B. tertiary < secondary < primary
C. secondary < primary < tertiary
D. primary = secondary = tertiary
Answer: A
Explanation: Alkyl groups stabilise carbocations via +I effect.
29. Free radicals contain
A. paired electrons
B. no electrons
C. unpaired electron
D. positive charge
Answer: C
Explanation: Free radicals have one unpaired electron.
Section K: Purification and Qualitative Analysis
30. Impure organic compounds are purified by
A. chromatography
B. crystallisation
C. distillation
D. all of these
Answer: D
Explanation: Different methods are used based on compound nature.
31. Technique used to separate coloured substances is
A. distillation
B. crystallisation
C. chromatography
D. sublimation
Answer: C
Explanation: Chromatography separates based on adsorption.
32. Sublimation is used when compound
A. is liquid
B. decomposes on heating
C. changes directly from solid to vapour
D. dissolves in water
Answer: C
Explanation: Sublimable solids bypass liquid state.
Section L: Quantitative Analysis
33. Estimation of carbon and hydrogen is done by
A. Dumas method
B. Kjeldahl method
C. Liebig method
D. Lassaigne’s test
Answer: C
Explanation: Liebig method estimates C and H.
34. Kjeldahl method is used to estimate
A. nitrogen
B. halogens
C. sulphur
D. oxygen
Answer: A
Explanation: It estimates nitrogen in organic compounds.
35. Lassaigne’s test is used for detecting
A. carbon
B. nitrogen, sulphur, halogens
C. hydrogen
D. oxygen
Answer: B
Explanation: Sodium fusion test identifies these elements.
Section M: Conceptual NCERT-Based MCQs
36. Organic compounds generally have
A. ionic bonds
B. metallic bonds
C. covalent bonds
D. hydrogen bonds only
Answer: C
Explanation: Carbon forms covalent bonds.
37. Higher boiling point of alcohols is due to
A. van der Waals forces
B. hydrogen bonding
C. dipole moment
D. molecular mass only
Answer: B
Explanation: Hydrogen bonding increases boiling point.
38. Which compound shows maximum hydrogen bonding?
A. CH₄
B. C₂H₆
C. CH₃OH
D. C₂H₄
Answer: C
Explanation: Methanol contains –OH group.
Section N: Application-Based MCQs
39. Which organic compound is used as solvent?
A. Methanol
B. Ether
C. Acetone
D. All of these
Answer: D
Explanation: Many organic compounds are used as solvents.
40. Ethanol is classified as
A. primary alcohol
B. secondary alcohol
C. tertiary alcohol
D. phenol
Answer: A
Explanation: –OH is attached to primary carbon.
Section O: High-Order Conceptual MCQs
41. Tautomerism is a type of
A. chain isomerism
B. functional isomerism
C. dynamic equilibrium
D. optical isomerism
Answer: C
Explanation: Tautomers interconvert dynamically.
42. Which effect stabilises alkenes?
A. Inductive effect
B. Hyperconjugation
C. Resonance
D. Hydrogen bonding
Answer: B
Explanation: Hyperconjugation stabilises alkenes.
43. Organic reactions generally involve breaking of
A. ionic bonds
B. covalent bonds
C. metallic bonds
D. hydrogen bonds only
Answer: B
Explanation: Organic reactions involve covalent bond cleavage.
44. Electrophiles are
A. electron-rich species
B. proton donors
C. electron-deficient species
D. neutral species
Answer: C
Explanation: Electrophiles seek electrons.
45. Nucleophiles are
A. electron-deficient
B. electron-rich
C. positively charged only
D. neutral only
Answer: B
Explanation: Nucleophiles donate electron pairs.
Section P: Assertion-Type and Final MCQs
46. Organic chemistry is also called chemistry of life because
A. all living things contain carbon compounds
B. carbon is radioactive
C. carbon forms ionic bonds
D. carbon is metallic
Answer: A
Explanation: Biomolecules are carbon-based.
47. Benzene is classified as
A. aliphatic compound
B. aromatic compound
C. saturated compound
D. alicyclic compound
Answer: B
Explanation: Benzene shows aromaticity.
48. Which property makes carbon compounds stable?
A. high bond energy of C–C bond
B. low atomic mass
C. metallic nature
D. ionic bonding
Answer: A
Explanation: Strong C–C bonds give stability.
49. Organic compounds generally have
A. high melting points
B. low melting points
C. very high density
D. ionic nature
Answer: B
Explanation: Weak intermolecular forces lower melting points.
50. Study of organic chemistry mainly helps in understanding
A. metals
B. acids and bases only
C. life processes and materials
D. nuclear reactions
Answer: C
Explanation: Organic chemistry explains biomolecules and materials.
✅ Completion Note
This completes a fully NCERT-aligned, CBSE-standard set of 50 MCQs on Some Basic Principles of Organic Chemistry, ideal for concept clarity, revision, and board exam preparation.