Exam-Focused MCQs for CBSE Class 12 Chemistry (NCERT Based)

Course: CBSE Class 12 Chemistry
Section: Exam-Focused MCQs for CBSE Class 12 Chemistry
Coverage: Physical, Organic & Inorganic Chemistry (Strictly NCERT)

The following 50 Multiple Choice Questions (MCQs) are carefully selected from high-weightage NCERT concepts, definitions, reactions, trends, and applications that are frequently tested in CBSE board exams. Each MCQ includes the correct answer with a clear, exam-oriented explanation. Questions are arranged section-wise for systematic revision.

Section A: Physical Chemistry (Solutions, Electrochemistry, Kinetics)

Q1. Raoult’s law is applicable to

(a) Ideal solutions only
(b) Non-ideal solutions only
(c) Colloidal solutions
(d) Electrolytic solutions

Answer: (a)
Explanation: Raoult’s law is strictly valid for ideal solutions where intermolecular interactions are similar.

Q2. The unit of molality is

(a) mol L⁻¹
(b) mol kg⁻¹
(c) g L⁻¹
(d) kg mol⁻¹

Answer: (b)
Explanation: Molality is defined as moles of solute per kilogram of solvent.

Q3. The van’t Hoff factor (i) for NaCl in water is approximately

(a) 0.5
(b) 1
(c) 2
(d) 3

Answer: (c)
Explanation: NaCl dissociates into Na⁺ and Cl⁻ ions, giving i ≈ 2.

Q4. The standard electrode potential of hydrogen electrode is

(a) +1.0 V
(b) –1.0 V
(c) 0.0 V
(d) +0.76 V

Answer: (c)
Explanation: The standard hydrogen electrode (SHE) is assigned zero potential by convention.

Q5. A reaction with half-life independent of initial concentration follows

(a) Zero order kinetics
(b) First order kinetics
(c) Second order kinetics
(d) Pseudo-first order

Answer: (b)
Explanation: For first-order reactions, half-life is constant and independent of concentration.

Q6. Rate constant of a reaction depends on

(a) Initial concentration
(b) Time
(c) Temperature
(d) Pressure only

Answer: (c)
Explanation: Rate constant depends on temperature as explained by Arrhenius equation.

Q7. The emf of an electrochemical cell is maximum when

(a) Cell reaction is at equilibrium
(b) No current flows
(c) Current is maximum
(d) Resistance is zero

Answer: (b)
Explanation: EMF is measured under open-circuit conditions when no current flows.

Q8. Conductance of a solution depends on

(a) Nature of electrolyte only
(b) Temperature only
(c) Cell constant only
(d) Concentration, temperature and nature of electrolyte

Answer: (d)
Explanation: All three factors affect ionic mobility and hence conductance.

Section B: Inorganic Chemistry (d- & f-Block, Coordination, p-Block)

Q9. Transition elements show variable oxidation states due to

(a) High electronegativity
(b) Partially filled d-orbitals
(c) Large atomic size
(d) Low ionisation energy only

Answer: (b)
Explanation: Similar energy levels of (n–1)d and ns orbitals allow variable oxidation states.

Q10. The colour of transition metal ions is due to

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

Answer: (b)
Explanation: Absorption of visible light promotes electrons between split d-orbitals.

Q11. Which of the following is a lanthanoid?

(a) Sc
(b) Ce
(c) Th
(d) U

Answer: (b)
Explanation: Cerium (Ce) belongs to the lanthanoid series (4f-block).

Q12. Lanthanoid contraction is caused by

(a) Poor shielding by 4f electrons
(b) Increase in nuclear charge only
(c) Strong metallic bonding
(d) Decrease in atomic mass

Answer: (a)
Explanation: 4f electrons shield nuclear charge poorly, causing size reduction.

Q13. The 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 directly bonded to iron.

Q14. Which ligand is bidentate?

(a) NH₃
(b) H₂O
(c) oxalate
(d) Cl⁻

Answer: (c)
Explanation: Oxalate ion attaches through two donor atoms.

Q15. The IUPAC name of [Co(NH₃)₆]Cl₃ is

(a) Hexaammine cobalt chloride
(b) Hexaammine cobalt(III) chloride
(c) Cobalt ammine chloride
(d) Triammine cobalt chloride

Answer: (b)
Explanation: Oxidation state of Co is +3, hence cobalt(III).

Q16. Which p-block element shows maximum catenation?

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

Answer: (c)
Explanation: Carbon forms stable C–C bonds, showing maximum catenation.

Q17. SF₆ has which geometry?

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

Answer: (d)
Explanation: Six bonding pairs around sulphur give octahedral geometry.

Section C: Organic Chemistry (Haloalkanes, Alcohols, Aldehydes, Amines)

Q18. The C–X bond length in haloalkanes increases from

(a) C–F < C–Cl < C–Br < C–I
(b) C–I < C–Br < C–Cl < C–F
(c) All equal
(d) Random order

Answer: (a)
Explanation: Bond length increases with atomic size of halogen.

Q19. 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, favouring SN1.

Q20. Lucas test distinguishes

(a) Aldehydes and ketones
(b) Primary, secondary and tertiary alcohols
(c) Alkanes and alkenes
(d) Phenols and ethers

Answer: (b)
Explanation: Reaction rate with Lucas reagent varies with alcohol type.

Q21. Phenol is more acidic than ethanol because

(a) Phenoxide ion is resonance stabilised
(b) Ethanol is basic
(c) Phenol has more hydrogen bonds
(d) Phenol has higher molecular mass

Answer: (a)
Explanation: Resonance stabilisation of phenoxide ion increases acidity.

Q22. Which reagent distinguishes aldehydes from ketones?

(a) Fehling’s solution
(b) Tollens’ reagent
(c) Both (a) and (b)
(d) NaOH

Answer: (c)
Explanation: Aldehydes give positive tests; ketones generally do not.

Q23. Formaldehyde gives Cannizzaro reaction because it

(a) Has α-hydrogen
(b) Lacks α-hydrogen
(c) Is aromatic
(d) Is unsaturated

Answer: (b)
Explanation: Aldehydes without α-hydrogen undergo Cannizzaro reaction.

Q24. 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 is delocalised into benzene ring.

Q25. Diazonium salts are prepared below 5 °C because

(a) Reaction is slow
(b) Salts are explosive at higher temperature
(c) Reaction is exothermic
(d) Acid decomposes

Answer: (b)
Explanation: Aryl diazonium salts are unstable at higher temperatures.

Section D: Biomolecules, Polymers & Chemistry in Everyday Life

Q26. Glucose is an example of

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

Answer: (c)
Explanation: Glucose is the simplest carbohydrate unit.

Q27. The linkage between amino acids in proteins is

(a) Glycosidic
(b) Peptide
(c) Ester
(d) Hydrogen

Answer: (b)
Explanation: Proteins are polymers of amino acids linked by peptide bonds.

Q28. Nylon-6,6 is a

(a) Addition polymer
(b) Natural polymer
(c) Condensation polymer
(d) Elastomer

Answer: (c)
Explanation: Nylon-6,6 forms by condensation of diamine and dicarboxylic acid.

Q29. 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)
Explanation: Buna-S is styrene-butadiene rubber.

Q30. Analgesics are drugs used to

(a) Kill bacteria
(b) Reduce fever
(c) Relieve pain
(d) Induce sleep

Answer: (c)
Explanation: Analgesics act on pain receptors or CNS.

Q31. Which drug is a non-narcotic analgesic?

(a) Morphine
(b) Codeine
(c) Aspirin
(d) Heroin

Answer: (c)
Explanation: Aspirin relieves pain without causing addiction.

Q32. Antibiotics are ineffective against

(a) Bacteria
(b) Fungi
(c) Viruses
(d) Protozoa

Answer: (c)
Explanation: Antibiotics target bacterial metabolism, not viruses.

Q33. Detergents are more effective than soaps in hard water because

(a) They are acidic
(b) They do not form scum
(c) They have shorter chains
(d) They are natural

Answer: (b)
Explanation: Detergents do not precipitate with Ca²⁺/Mg²⁺ ions.

Q34. Artificial sweeteners are preferred because they

(a) Are natural
(b) Provide energy
(c) Are low-calorie
(d) Increase appetite

Answer: (c)
Explanation: They provide sweetness without adding calories.

Section E: High-Yield Mixed MCQs (Board Favourite)

Q35. Order of reducing power is

Zn²⁺/Zn < Cu²⁺/Cu < Ag⁺/Ag because
(a) E° values increase
(b) Atomic size increases
(c) Ionisation energy decreases
(d) Reactivity increases

Answer: (a)
Explanation: Higher standard reduction potential means weaker reducing agent.

Q36. A 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)
Explanation: Concentration decreases linearly with time.

Q37. Chelation increases stability of complexes due to

(a) Large size
(b) Entropy increase
(c) High charge
(d) Steric effect

Answer: (b)
Explanation: Chelate effect is entropy driven.

Q38. The geometry of [Ni(CN)₄]²⁻ is

(a) Tetrahedral
(b) Square planar
(c) Octahedral
(d) Linear

Answer: (b)
Explanation: Strong field CN⁻ ligand causes pairing.

Q39. Phenol reacts with bromine water to form

(a) Bromobenzene
(b) o-bromophenol
(c) p-bromophenol
(d) 2,4,6-tribromophenol

Answer: (d)
Explanation: Activated ring undergoes multiple substitution.

Q40. Gabriel phthalimide synthesis is used to prepare

(a) Secondary amines
(b) Tertiary amines
(c) Primary amines
(d) Aromatic amines

Answer: (c)
Explanation: It selectively yields primary amines.

Q41. The monomer of Teflon is

(a) Vinyl chloride
(b) Tetrafluoroethylene
(c) Ethylene
(d) Styrene

Answer: (b)
Explanation: Polymerisation of tetrafluoroethylene forms Teflon.

Q42. The major source of energy in living systems is

(a) Proteins
(b) Fats
(c) Carbohydrates
(d) Vitamins

Answer: (c)
Explanation: Glucose is the primary energy source.

Q43. Which vitamin is water-soluble?

(a) A
(b) D
(c) E
(d) C

Answer: (d)
Explanation: Vitamin C dissolves in water.

Q44. Insulin is

(a) Enzyme
(b) Hormone
(c) Vitamin
(d) Lipid

Answer: (b)
Explanation: Insulin is a protein hormone.

Q45. Which soap is used for bathing?

(a) Sodium soap
(b) Potassium soap
(c) Calcium soap
(d) Magnesium soap

Answer: (b)
Explanation: Potassium soaps are soft and suitable for bathing.

Q46. The hydrophilic part of soap is

(a) Hydrocarbon chain
(b) –COO⁻ group
(c) Alkyl group
(d) Benzene ring

Answer: (b)
Explanation: Carboxylate ion attracts water molecules.

Q47. Excess use of antibiotics leads to

(a) Faster recovery
(b) Immunity loss
(c) Antibiotic resistance
(d) Vaccination

Answer: (c)
Explanation: Misuse allows bacteria to develop resistance.

Q48. Which drug is used as a tranquilizer?

(a) Aspirin
(b) Diazepam
(c) Penicillin
(d) Paracetamol

Answer: (b)
Explanation: Diazepam reduces anxiety and stress.

Q49. The pH of blood is approximately

(a) 5.6
(b) 6.8
(c) 7.4
(d) 8.5

Answer: (c)
Explanation: Blood pH is maintained around 7.4 for proper metabolism.

Q50. NCERT-based Chemistry MCQs mainly test

(a) Memorisation only
(b) Numerical skills only
(c) Conceptual clarity and applications
(d) Advanced research topics

Answer: (c)
Explanation: CBSE focuses on core concepts, trends, and NCERT applications.

✅ Exam Utility

• 100% NCERT aligned
• Ideal for CBSE Class 12 Boards
• Covers all units in exam-oriented form
• Suitable for revision, tests, and worksheets