High-Scoring Chemistry MCQs for CBSE Class 12 Students
High-Scoring Chemistry MCQs for CBSE Class 12 Students (NCERT Based)
Course: CBSE Class 12 Chemistry
Section: Exam-Focused MCQs for CBSE Class 12 Chemistry
This set of 50 high-scoring MCQs is strictly based on the NCERT syllabus and curated from frequently tested CBSE board exam concepts. Each question includes the correct answer with a clear, concept-clearing explanation, helping students maximise marks through smart revision. The questions are arranged section-wise to ensure balanced coverage of Physical, Inorganic, and Organic Chemistry.
Section A: Physical Chemistry (Sure-Shot Scoring 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) Inversely proportional to temperature
(d) Independent of composition
Answer: (b)
Explanation: According to Raoult’s law, partial vapour pressure is directly proportional to the mole fraction of the component in an ideal solution.
Q2. Molality is preferred over molarity in colligative properties because it
(a) Is easier to calculate
(b) Depends on volume
(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 (i) for CaCl₂ in aqueous solution is
(a) 1
(b) 2
(c) 3
(d) 4
Answer: (c)
Explanation: CaCl₂ dissociates into Ca²⁺ and 2Cl⁻ ions, giving three particles.
Q4. The standard electrode potential of a galvanic cell is measured when
(a) Maximum current flows
(b) Reaction reaches equilibrium
(c) No current flows
(d) Resistance is zero
Answer: (c)
Explanation: EMF is measured under open-circuit conditions when no current flows.
Q5. The half-life of a first-order reaction depends on
(a) Initial concentration
(b) Rate constant only
(c) Temperature only
(d) Time
Answer: (b)
Explanation: For first-order reactions, half-life depends only on the rate constant.
Q6. The 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)
Explanation: Zero-order reactions have rate independent of concentration.
Q7. Kohlrausch’s law is useful for calculating
(a) pH of solution
(b) Degree of dissociation
(c) Limiting molar conductivity
(d) Cell constant
Answer: (c)
Explanation: It helps determine limiting molar conductivity of weak electrolytes.
Q8. Increase in temperature generally
(a) Decreases rate constant
(b) Has no effect on reaction rate
(c) Increases rate constant
(d) Stops the reaction
Answer: (c)
Explanation: According to Arrhenius equation, rate constant increases with temperature.
Section B: Inorganic Chemistry (High-Yield Board Areas)
Q9. Transition metals show variable oxidation states because of
(a) Large atomic size
(b) High melting points
(c) Partially filled d-orbitals
(d) High electronegativity
Answer: (c)
Explanation: Small energy difference between ns and (n–1)d orbitals allows variable oxidation states.
Q10. The colour of transition metal complexes is due to
(a) Charge transfer
(b) d–d transitions
(c) f–f transitions
(d) Metallic bonding
Answer: (b)
Explanation: Absorption of visible light causes d–d electronic transitions.
Q11. Lanthanoid contraction occurs due to
(a) High atomic mass
(b) Poor shielding by 4f electrons
(c) Strong metallic bonding
(d) Increase in density
Answer: (b)
Explanation: 4f electrons shield nuclear charge poorly, reducing atomic size.
Q12. Coordination number of metal in [Co(NH₃)₆]³⁺ is
(a) 3
(b) 4
(c) 5
(d) 6
Answer: (d)
Explanation: Six ammonia ligands are directly bonded to cobalt.
Q13. Oxalate ion is an example of
(a) Monodentate ligand
(b) Ambidentate ligand
(c) Bidentate ligand
(d) Polydentate ligand
Answer: (c)
Explanation: Oxalate coordinates through two donor atoms.
Q14. The geometry of SF₆ molecule is
(a) Tetrahedral
(b) Trigonal bipyramidal
(c) Square planar
(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 bonding gives carbon maximum catenation.
Section C: Organic Chemistry (Reaction & Logic Based MCQs)
Q16. SN1 reaction rate depends on
(a) Concentration of nucleophile
(b) Stability of carbocation
(c) Strength of nucleophile
(d) Solvent polarity only
Answer: (b)
Explanation: Formation of carbocation is the rate-determining step.
Q17. Lucas test is used to distinguish
(a) Aldehydes and ketones
(b) Alcohols
(c) Phenols and ethers
(d) Amines
Answer: (b)
Explanation: Reaction time with Lucas reagent varies for 1°, 2°, and 3° alcohols.
Q18. Phenol is more acidic than ethanol due to
(a) +I effect
(b) –I effect
(c) Resonance stabilization
(d) Hydrogen bonding
Answer: (c)
Explanation: Phenoxide ion is stabilised by resonance.
Q19. Tollens’ reagent is used to identify
(a) Ketones
(b) Alcohols
(c) Aldehydes
(d) Amines
Answer: (c)
Explanation: Aldehydes reduce Tollens’ reagent to silver mirror.
Q20. Cannizzaro reaction occurs in aldehydes
(a) With α-hydrogen
(b) Without α-hydrogen
(c) Aromatic only
(d) Aliphatic only
Answer: (b)
Explanation: Absence of α-hydrogen is required.
Q21. Aniline is less basic than methylamine because
(a) +I effect
(b) –I effect
(c) Resonance
(d) Steric hindrance
Answer: (c)
Explanation: Lone pair on nitrogen delocalises into benzene ring.
Q22. Diazotisation of aniline is carried out below 5 °C because
(a) Reaction is slow
(b) Diazonium salt is unstable at higher temperature
(c) Acid decomposes
(d) Reaction is endothermic
Answer: (b)
Explanation: Diazonium salts decompose at higher temperatures.
Section D: Biomolecules, Polymers & Everyday Chemistry
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) Kill bacteria
(b) Reduce fever
(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. Artificial sweeteners are preferred because they
(a) Increase energy
(b) Are low-calorie
(c) Are natural
(d) Improve digestion
Answer: (b)
Q38. Excessive use of antibiotics leads to
(a) Faster cure
(b) Resistance
(c) Immunity boost
(d) Vaccination
Answer: (b)
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: Board Logic & Trend-Based MCQs (Q41–Q50)
Q41. The 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 with increase in standard reduction potential (E°). Since E° values increase from Zn → Cu → Ag, their reducing power decreases accordingly.
Q42. The strongest acid among hydrogen halides is
(a) HF
(b) HCl
(c) HBr
(d) HI
Answer: (d)
Explanation: Acidic strength increases down the group due to decrease in bond dissociation energy. HI ionises most easily.
Q43. The most electronegative element in the periodic table is
(a) Oxygen
(b) Nitrogen
(c) Chlorine
(d) Fluorine
Answer: (d)
Explanation: Fluorine has the smallest atomic size and highest effective nuclear charge, giving it maximum electronegativity.
Q44. Maximum hydrogen bonding is shown by
(a) NH₃
(b) HF
(c) H₂O
(d) CH₄
Answer: (c)
Explanation: Each water molecule can form up to four hydrogen bonds, resulting in extensive hydrogen bonding.
Q45. The hybridisation of boron 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 shape.
Q46. The molecular shape of SF₆ is
(a) Tetrahedral
(b) Square planar
(c) Trigonal bipyramidal
(d) Octahedral
Answer: (d)
Explanation: Sulphur forms six σ bonds with fluorine atoms, giving octahedral geometry.
Q47. The best laboratory 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 selectively forms primary amines without producing secondary or tertiary amines.
Q48. Aldol condensation is shown by aldehydes and ketones that
(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.
Q49. 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 decomposed by microorganisms and are environmentally safer.
Q50. CBSE Class 12 Chemistry board questions mainly focus on
(a) Rote memorisation
(b) Advanced numerical problems
(c) Conceptual clarity and NCERT applications
(d) Research-based chemistry
Answer: (c)
Explanation: CBSE exams are strictly NCERT-based and test understanding of concepts, trends, reactions, and applications.
✅ Final Completion Status
- Q1–Q50 fully completed
- Strictly NCERT aligned
- Covers logic, trends, reactions, biomolecules & everyday chemistry
- Ideal for high-scoring CBSE Class 12 board preparation