CBSE Class 12 Chemistry MCQs for Last-Minute Exam Revision (NCERT Based)

Course: CBSE Class 12 Chemistry
Section: Exam-Focused MCQs for CBSE Class 12 Chemistry

This 50-MCQ last-minute revision set is strictly NCERT-aligned and designed for quick recall, concept clarity, and maximum scoring in the CBSE Class 12 Chemistry board exam. The questions focus on high-frequency board areas, formulas, reactions, trends, and definitions. Each MCQ includes the correct answer with a crisp, exam-ready explanation. The set is arranged section-wise for efficient revision.

Section A: Physical Chemistry (Fast-Scoring Concepts)

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 for ideal solutions where intermolecular interactions 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 (i) for AlCl₃ in aqueous solution is

(a) 1
(b) 2
(c) 3
(d) 4

Answer: (d)
Explanation: AlCl₃ dissociates into Al³⁺ + 3Cl⁻ → total 4 ions.

Q4. EMF of a galvanic cell is maximum when

(a) Current flows
(b) Reaction is at equilibrium
(c) No current flows
(d) Resistance is zero

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) Temperature only
(d) Time

Answer: (b)
Explanation: ( t_{1/2} = \frac{0.693}{k} ).

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 constant increases with

(a) Decrease in temperature
(b) Increase in activation energy
(c) Increase in temperature
(d) Decrease in concentration

Answer: (c)
Explanation: Higher temperature increases fraction of effective collisions.

Q8. Kohlrausch’s law is used to calculate

(a) pH
(b) Cell constant
(c) Limiting molar conductivity
(d) Degree of hydration

Answer: (c)

Section B: Inorganic Chemistry (One-Line Board Favourites)

Q9. Variable oxidation states in transition metals are due to

(a) Large atomic size
(b) High density
(c) Partially filled d-orbitals
(d) High melting points

Answer: (c)

Q10. Colour of transition metal ions arises due to

(a) f–f transitions
(b) Charge transfer
(c) d–d transitions
(d) Metallic bonding

Answer: (c)

Q11. Lanthanoid contraction occurs due to

(a) High atomic mass
(b) Poor shielding by 4f electrons
(c) Metallic bonding
(d) Increase in density

Answer: (b)

Q12. Coordination number of metal 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. Shape of SF₆ molecule is

(a) Tetrahedral
(b) Square planar
(c) Trigonal bipyramidal
(d) Octahedral

Answer: (d)

Q15. Element showing maximum catenation is

(a) Silicon
(b) Carbon
(c) Nitrogen
(d) Oxygen

Answer: (b)

Section C: Organic Chemistry (Reaction-Trigger MCQs)

Q16. SN1 reactions are favoured by

(a) Primary carbocation
(b) Secondary carbocation
(c) Tertiary carbocation
(d) Methyl carbocation

Answer: (c)

Q17. Lucas test distinguishes

(a) Aldehydes and ketones
(b) Phenols and alcohols
(c) Primary, secondary and tertiary alcohols
(d) Amines

Answer: (c)

Q18. Phenol is more acidic than ethanol due to

(a) +I effect
(b) –I effect
(c) Resonance stabilisation
(d) Hydrogen bonding

Answer: (c)

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 more acid
(d) Are endothermic

Answer: (b)

Section D: Biomolecules, Polymers & Everyday Chemistry

Q23. Glucose is a

(a) Disaccharide
(b) Polysaccharide
(c) Monosaccharide
(d) Glycoprotein

Answer: (c)

Q24. Peptide bond links

(a) Sugars
(b) Amino acids
(c) Fatty acids
(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 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: Ultra-Quick Board Logic 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: Key Board Trends – Rapid 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 as standard reduction potential (E°) increases. Since E° values increase from Zn → Cu → 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 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 with fluorine atoms, requiring sp² hybridisation and giving 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 two lone pairs arranged opposite to each other, resulting in 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 decomposed by microorganisms and hence are biodegradable.

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 necessary for enolate ion formation, which initiates aldol reaction.

Q47. The best laboratory method for preparing 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 forming secondary or tertiary amines.

Q48. Electrical conductance of an electrolyte solution increases with

(a) Increase in concentration
(b) Decrease in temperature
(c) Increase in temperature
(d) Increase in pressure

Answer: (c)
Explanation: Higher temperature increases ionic mobility, leading to higher conductance.

Q49. Which tests are used for identification of glucose?

(a) Fehling’s test only
(b) Tollens’ test only
(c) Benedict’s test only
(d) 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-oriented chemistry
(d) NCERT concepts and applications

Answer: (d)
Explanation: CBSE board exams are strictly NCERT-based and emphasise conceptual clarity, trends, reactions, and real-life applications.

✅ Final Rapid Recall Summary

• Covers most predictable board questions
• Ideal for last 24–48 hours revision
• Fully NCERT aligned
• Designed for quick marks gain