Board Exam Oriented MCQs for Class 12 Chemistry
Board Exam Oriented MCQs for Class 12 Chemistry (NCERT Based)
Course: CBSE Class 12 Chemistry
Section: Exam-Focused MCQs for CBSE Class 12 Chemistry
This set of 50 board-exam-oriented MCQs is strictly based on the NCERT syllabus and designed to match the logic, trends, and difficulty level of CBSE Class 12 Chemistry board examinations. Each question is supported by a clear, concept-clearing explanation, making it ideal for systematic revision and scoring improvement. The MCQs are arranged section-wise for balanced syllabus coverage.
Section A: Physical Chemistry (High-Weightage Board Areas)
Q1. Raoult’s law is applicable to
(a) Ideal solutions
(b) Non-ideal solutions
(c) Colloids
(d) Electrolytes
Answer: (a)
Explanation: Raoult’s law holds true for ideal solutions where intermolecular forces between components are similar.
Q2. Molality is preferred over molarity in colligative properties because it
(a) Depends on volume
(b) Is temperature dependent
(c) Is temperature independent
(d) Uses litres of solution
Answer: (c)
Explanation: Molality depends on mass of solvent, which does not change with temperature.
Q3. The van’t Hoff factor for MgCl₂ in aqueous solution is
(a) 1
(b) 2
(c) 3
(d) 4
Answer: (c)
Explanation: MgCl₂ dissociates into Mg²⁺ and 2Cl⁻ ions, giving three particles.
Q4. EMF of a galvanic cell is measured when
(a) Maximum current flows
(b) Reaction is at equilibrium
(c) No current flows
(d) Resistance is zero
Answer: (c)
Explanation: EMF is defined under open-circuit conditions.
Q5. The half-life of a first-order reaction depends on
(a) Initial concentration
(b) Rate constant
(c) Time
(d) Pressure
Answer: (b)
Explanation: For first-order reactions, half-life is independent of initial concentration.
Q6. Unit of rate constant for 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)
Explanation: Rate = k for zero-order reactions.
Q7. According to Arrhenius equation, rate of reaction increases with
(a) Increase in activation energy
(b) Decrease in temperature
(c) Increase in temperature
(d) Decrease in concentration
Answer: (c)
Explanation: Higher temperature increases the number of effective molecular collisions.
Q8. Kohlrausch’s law is used to calculate
(a) pH of solution
(b) Limiting molar conductivity
(c) Cell constant
(d) Degree of hydration
Answer: (b)
Explanation: It allows calculation of limiting molar conductivity of weak electrolytes.
Section B: Inorganic Chemistry (Frequently Tested Concepts)
Q9. Variable oxidation states in transition metals are due to
(a) Large atomic size
(b) High melting points
(c) Partially filled d-orbitals
(d) High density
Answer: (c)
Explanation: Similar energies of ns and (n–1)d orbitals enable variable oxidation states.
Q10. The colour of transition metal complexes arises due to
(a) f–f transitions
(b) d–d transitions
(c) Charge transfer
(d) Metallic bonding
Answer: (b)
Explanation: Absorption of visible light promotes electrons between split d-orbitals.
Q11. Lanthanoid contraction occurs because of
(a) High atomic mass
(b) Poor shielding by 4f electrons
(c) Metallic bonding
(d) High density
Answer: (b)
Explanation: 4f electrons shield nuclear charge poorly, causing size reduction.
Q12. Coordination number of Fe in [Fe(CN)₆]³⁻ is
(a) 3
(b) 4
(c) 5
(d) 6
Answer: (d)
Explanation: Six cyanide ligands are bonded to iron.
Q13. Oxalate ion acts as a
(a) Monodentate ligand
(b) Ambidentate ligand
(c) Bidentate ligand
(d) Neutral ligand
Answer: (c)
Explanation: Oxalate donates two pairs of electrons to the metal ion.
Q14. The geometry of SF₆ molecule is
(a) Tetrahedral
(b) Square planar
(c) Trigonal bipyramidal
(d) Octahedral
Answer: (d)
Explanation: Six bond pairs around sulphur give octahedral geometry.
Q15. Maximum catenation is shown by
(a) Silicon
(b) Carbon
(c) Nitrogen
(d) Oxygen
Answer: (b)
Explanation: Strong C–C bonds allow carbon to form long chains.
Section C: Organic Chemistry (Reaction-Based Board MCQs)
Q16. SN1 reactions are favoured by
(a) Primary carbocations
(b) Secondary carbocations
(c) Tertiary carbocations
(d) Methyl carbocations
Answer: (c)
Explanation: Tertiary carbocations are most stable.
Q17. Lucas test is used to distinguish
(a) Aldehydes and ketones
(b) Phenols and ethers
(c) Primary, secondary and tertiary alcohols
(d) Amines
Answer: (c)
Explanation: Reaction rate differs for different classes of alcohols.
Q18. Phenol is more acidic than ethanol due to
(a) Inductive effect
(b) Resonance stabilisation
(c) Hydrogen bonding
(d) Molecular mass
Answer: (b)
Explanation: Phenoxide ion is resonance-stabilised.
Q19. Tollens’ reagent gives silver mirror with
(a) Ketones
(b) Aldehydes
(c) Alcohols
(d) Acids
Answer: (b)
Explanation: Aldehydes are easily oxidised.
Q20. Cannizzaro reaction is shown by aldehydes
(a) With α-hydrogen
(b) Without α-hydrogen
(c) Aromatic only
(d) Aliphatic only
Answer: (b)
Explanation: Aldehydes lacking α-hydrogen undergo disproportionation.
Q21. Aniline is less basic than methylamine due to
(a) +I effect
(b) –I effect
(c) Resonance
(d) Steric hindrance
Answer: (c)
Explanation: Lone pair on nitrogen delocalises into benzene ring.
Q22. Diazonium salts are prepared below 5 °C because
(a) Reaction is slow
(b) They are unstable at higher temperature
(c) Acid decomposes
(d) Reaction is endothermic
Answer: (b)
Explanation: Diazonium salts decompose at higher temperatures.
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) Glucose
(d) Nucleotides
Answer: (b)
Q25. Nylon-6,6 is formed by
(a) Addition polymerisation
(b) Condensation polymerisation
(c) Free-radical polymerisation
(d) Copolymerisation
Answer: (b)
Q26. 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)
Q27. Analgesics are drugs used to
(a) Reduce fever
(b) Kill bacteria
(c) Relieve pain
(d) Induce sleep
Answer: (c)
Q28. Which is a non-narcotic analgesic?
(a) Morphine
(b) Codeine
(c) Aspirin
(d) Heroin
Answer: (c)
Q29. Antibiotics are ineffective against
(a) Bacteria
(b) Fungi
(c) Viruses
(d) Protozoa
Answer: (c)
Q30. Detergents are preferred over soaps because they
(a) Are biodegradable
(b) Work in hard water
(c) Are natural
(d) Are cheaper
Answer: (b)
Section E: Board Logic & Trend-Based 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 classified as a
(a) Antibiotic
(b) Analgesic
(c) Tranquilizer
(d) Antipyretic
Answer: (c)
Section E: Rapid Board Recall MCQs (Q41–Q50)
Q41. The correct increasing order of reducing power of metals 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 as standard reduction potential (E°) increases. Since E° values increase from Zn to Cu to Ag, their reducing power decreases in the same order.
Q42. Which substance 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 in BF₃ molecule is
(a) sp
(b) sp²
(c) sp³
(d) dsp²
Answer: (b)
Explanation: Boron forms three σ bonds and has no lone pair, so it undergoes sp² hybridisation giving a trigonal planar structure.
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 placed opposite each other, resulting in a square planar geometry.
Q45. Which of the following detergents is biodegradable?
(a) Branched-chain detergents
(b) Phosphate detergents
(c) Straight-chain detergents
(d) Cationic detergents
Answer: (c)
Explanation: Straight-chain detergents are easily broken down by microorganisms and are environmentally safer.
Q46. Aldol reaction is shown by aldehydes and ketones which
(a) Are aromatic
(b) Are unsaturated
(c) Contain α-hydrogen
(d) Are acidic
Answer: (c)
Explanation: Presence of α-hydrogen is essential for formation of enolate ion in aldol reaction.
Q47. The best method for the 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 selectively yields primary amines without 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 increases ionic mobility, thus increasing conductance.
Q49. Glucose can be identified by
(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 gives positive results with both Fehling’s and Tollens’ reagents.
Q50. CBSE Class 12 Chemistry board examinations mainly focus on
(a) Rote memorisation
(b) Advanced numerical problems
(c) Research-based chemistry
(d) NCERT concepts and applications
Answer: (d)
Explanation: CBSE board exams strictly follow NCERT and test conceptual understanding, trends, reactions, and real-life applications.
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