Top Exam-Focused MCQs from NCERT Chemistry Class 12
Top Exam-Focused MCQs from NCERT Chemistry Class 12
Course: CBSE Class 12 Chemistry
Section: Exam-Focused MCQs for CBSE Class 12 Chemistry
This carefully curated set of 50 top exam-focused MCQs is strictly based on NCERT Class 12 Chemistry and reflects the most repeated concepts, reactions, trends, and definitions asked in CBSE board exams. Each MCQ is supported with a clear, concept-clearing explanation, making it ideal for exam-oriented preparation and revision.
Questions are arranged section-wise to ensure complete and balanced syllabus coverage.
Section A: Physical Chemistry (High-Scoring NCERT MCQs)
Q1. Raoult’s law states that the partial vapour pressure of a component is
(a) Equal to its mole fraction
(b) Proportional to its mole fraction
(c) Independent of temperature
(d) Independent of composition
Answer: (b)
Explanation: For ideal solutions, partial vapour pressure is directly proportional to mole fraction.
Q2. Molality is preferred over molarity for colligative properties because it
(a) Depends on volume
(b) Is temperature independent
(c) Is easier to calculate
(d) Uses litres of solution
Answer: (b)
Explanation: Molality depends on mass of solvent, which does not change with temperature.
Q3. The van’t Hoff factor for Na₂SO₄ in aqueous solution is
(a) 1
(b) 2
(c) 3
(d) 4
Answer: (c)
Explanation: Na₂SO₄ dissociates into 2Na⁺ and SO₄²⁻ ions, giving three particles.
Q4. EMF of an electrochemical cell is maximum when
(a) Current flows
(b) Reaction is at equilibrium
(c) No current flows
(d) Resistance is minimum
Answer: (c)
Explanation: EMF is measured under open-circuit conditions.
Q5. Half-life of a first-order reaction depends on
(a) Initial concentration
(b) Rate constant
(c) Time
(d) Pressure
Answer: (b)
Explanation: ( t_{1/2} = \frac{0.693}{k} ), independent of concentration.
Q6. Unit of rate constant for a zero-order reaction is
(a) s⁻¹
(b) mol L⁻¹ s⁻¹
(c) L mol⁻¹ s⁻¹
(d) mol² L⁻² s⁻¹
Answer: (b)
Q7. Rate constant of a reaction increases with
(a) Decrease in temperature
(b) Increase in activation energy
(c) Increase in temperature
(d) Decrease in concentration
Answer: (c)
Q8. Kohlrausch’s law is useful for calculating
(a) pH
(b) Limiting molar conductivity
(c) Cell constant
(d) Transport number
Answer: (b)
Section B: Inorganic Chemistry (Most Repeated NCERT MCQs)
Q9. Transition metals show variable oxidation states due to
(a) Large atomic size
(b) Partially filled d-orbitals
(c) High density
(d) Metallic bonding
Answer: (b)
Q10. Colour of transition metal ions is due to
(a) Charge transfer
(b) d–d transitions
(c) f–f transitions
(d) Metallic bonding
Answer: (b)
Q11. Lanthanoid contraction occurs because of
(a) High atomic mass
(b) Poor shielding by 4f electrons
(c) Strong metallic bonding
(d) High density
Answer: (b)
Q12. Coordination number of Fe in [Fe(CN)₆]³⁻ is
(a) 3
(b) 4
(c) 5
(d) 6
Answer: (d)
Q13. Oxalate ion is a
(a) Monodentate ligand
(b) Ambidentate ligand
(c) Bidentate ligand
(d) Neutral ligand
Answer: (c)
Q14. Geometry of SF₆ molecule is
(a) Tetrahedral
(b) Square planar
(c) Trigonal bipyramidal
(d) Octahedral
Answer: (d)
Q15. Maximum catenation is shown by
(a) Nitrogen
(b) Oxygen
(c) Carbon
(d) Silicon
Answer: (c)
Section C: Organic Chemistry (Reaction-Based Exam MCQs)
Q16. SN1 reactions are favoured by
(a) Primary carbocations
(b) Secondary carbocations
(c) Tertiary carbocations
(d) Methyl carbocations
Answer: (c)
Q17. Lucas test is used to distinguish
(a) Aldehydes and ketones
(b) Alcohols
(c) Phenols and ethers
(d) Amines
Answer: (b)
Q18. Phenol is more acidic than ethanol due to
(a) Inductive effect
(b) Resonance stabilisation
(c) Hydrogen bonding
(d) Molecular mass
Answer: (b)
Q19. Tollens’ reagent gives silver mirror with
(a) Ketones
(b) Aldehydes
(c) Alcohols
(d) Acids
Answer: (b)
Q20. Cannizzaro reaction is shown by aldehydes
(a) With α-hydrogen
(b) Without α-hydrogen
(c) Aromatic only
(d) Aliphatic only
Answer: (b)
Q21. Aniline is less basic than methylamine due to
(a) +I effect
(b) –I effect
(c) Resonance
(d) Steric hindrance
Answer: (c)
Q22. Diazonium salts are prepared below 5 °C because they
(a) React slowly
(b) Are unstable at higher temperature
(c) Need excess acid
(d) Are endothermic
Answer: (b)
Section D: Biomolecules, Polymers & Chemistry in Everyday Life
Q23. Glucose is a
(a) Disaccharide
(b) Polysaccharide
(c) Monosaccharide
(d) Glycoprotein
Answer: (c)
Q24. Proteins are polymers of
(a) Fatty acids
(b) Amino acids
(c) Nucleotides
(d) Glucose
Answer: (b)
Q25. Peptide bond is formed between
(a) Two sugars
(b) Two amino acids
(c) Two fatty acids
(d) Two nucleotides
Answer: (b)
Q26. Nylon-6,6 is formed by
(a) Addition polymerisation
(b) Condensation polymerisation
(c) Free-radical polymerisation
(d) Copolymerisation
Answer: (b)
Q27. Buna-S is a copolymer of
(a) Butadiene and styrene
(b) Isoprene and styrene
(c) Ethene and propene
(d) Vinyl chloride and styrene
Answer: (a)
Q28. Analgesics are drugs used to
(a) Reduce fever
(b) Kill bacteria
(c) Relieve pain
(d) Induce sleep
Answer: (c)
Q29. Which is a non-narcotic analgesic?
(a) Morphine
(b) Codeine
(c) Aspirin
(d) Heroin
Answer: (c)
Q30. Antibiotics are ineffective against
(a) Bacteria
(b) Fungi
(c) Viruses
(d) Protozoa
Answer: (c)
Section E: Top Board Logic & Trend MCQs
Q31. Zero-order reaction shows linear plot of
(a) log[A] vs t
(b) 1/[A] vs t
(c) [A] vs t
(d) k vs t
Answer: (c)
Q32. Chelation increases stability of complexes due to
(a) Size effect
(b) Entropy increase
(c) Charge increase
(d) Steric effect
Answer: (b)
Q33. Monomer of Teflon is
(a) Ethene
(b) Styrene
(c) Vinyl chloride
(d) Tetrafluoroethylene
Answer: (d)
Q34. Vitamin C is
(a) Fat-soluble
(b) Water-soluble
(c) Hormone
(d) Enzyme
Answer: (b)
Q35. Insulin is a
(a) Vitamin
(b) Lipid
(c) Hormone
(d) Carbohydrate
Answer: (c)
Q36. Hydrophilic part of soap is
(a) Hydrocarbon chain
(b) –COO⁻ group
(c) Alkyl group
(d) Benzene ring
Answer: (b)
Q37. Strongest acid among hydrogen halides is
(a) HF
(b) HCl
(c) HBr
(d) HI
Answer: (d)
Q38. Most electronegative element is
(a) Oxygen
(b) Nitrogen
(c) Chlorine
(d) Fluorine
Answer: (d)
Q39. Approximate pH of human blood is
(a) 5.6
(b) 6.8
(c) 7.4
(d) 8.5
Answer: (c)
Q40. Diazepam is a
(a) Antibiotic
(b) Analgesic
(c) Tranquilizer
(d) Antipyretic
Answer: (c)
Section E: Ultra-Rapid NCERT Recall MCQs (Q41–Q50)
Q41. The correct increasing order of reducing power among Zn, Cu and Ag is
(a) Ag < Cu < Zn
(b) Cu < Zn < Ag
(c) Zn < Cu < Ag
(d) Ag < Zn < Cu
Answer: (c)
Explanation: Reducing power decreases with increase in standard reduction potential (E°). Since E° increases from Zn → Cu → Ag, reducing power decreases in the same order.
Q42. Which of the following shows maximum hydrogen bonding?
(a) NH₃
(b) HF
(c) H₂O
(d) CH₄
Answer: (c)
Explanation: Each water molecule can form up to four hydrogen bonds, resulting in extensive intermolecular hydrogen bonding.
Q43. The hybridisation of boron atom in BF₃ is
(a) sp
(b) sp²
(c) sp³
(d) dsp²
Answer: (b)
Explanation: Boron forms three σ bonds and has no lone pair, leading to sp² hybridisation and trigonal planar geometry.
Q44. The shape of XeF₄ molecule is
(a) Tetrahedral
(b) Square planar
(c) Trigonal bipyramidal
(d) Octahedral
Answer: (b)
Explanation: XeF₄ has four bond pairs and two lone pairs arranged opposite each other, giving a square planar shape.
Q45. Which detergents are biodegradable in nature?
(a) Branched-chain detergents
(b) Phosphate detergents
(c) Straight-chain detergents
(d) Cationic detergents
Answer: (c)
Explanation: Straight-chain detergents are easily decomposed by microorganisms and are environmentally friendly.
Q46. Aldol reaction is possible only in compounds that
(a) Are aromatic
(b) Are unsaturated
(c) Contain α-hydrogen
(d) Are acidic
Answer: (c)
Explanation: Presence of α-hydrogen is necessary for formation of enolate ion in aldol reaction.
Q47. The most suitable method for preparation of primary amines is
(a) Hoffmann bromamide reaction
(b) Gabriel phthalimide synthesis
(c) Reduction of nitro compounds
(d) Ammonolysis of alkyl halides
Answer: (b)
Explanation: Gabriel synthesis gives only primary amines and avoids formation of secondary or tertiary amines.
Q48. Electrical conductance of an electrolyte solution increases with
(a) Increase in pressure
(b) Decrease in temperature
(c) Increase in temperature
(d) Decrease in concentration
Answer: (c)
Explanation: Increase in temperature enhances ionic mobility, thereby increasing conductance.
Q49. Glucose gives positive result with
(a) Fehling’s test only
(b) Tollens’ test only
(c) Benedict’s test only
(d) Both Fehling’s and Tollens’ tests
Answer: (d)
Explanation: Glucose is a reducing sugar and reduces both Fehling’s and Tollens’ reagents.
Q50. CBSE Class 12 Chemistry board examinations mainly emphasise
(a) Rote memorisation
(b) Advanced numerical problems
(c) Research-level chemistry
(d) NCERT concepts and applications
Answer: (d)
Explanation: CBSE papers are strictly NCERT-based and focus on conceptual clarity, trends, reactions, and real-life applications.
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