Chemistry Important Questions Class 12 CBSE — Chapter Wise

CBSE Class 12 Chemistry is 70 marks theory + 30 marks practical. In the 2026-27 syllabus, organic chemistry carries the most marks (33), physical chemistry 23 and inorganic 14. Below are practice questions of the kinds that come up often, chapter by chapter, for the Board exams 2027.

Marks by Branch (2026-27)

Solid State and p-Block Elements are not in the syllabus; Surface Chemistry, Isolation of Elements, Polymers and Chemistry in Everyday Life are assessed only by your school.

Physical Chemistry

Solutions

• State Raoult's law. Explain positive and negative deviations, with examples and graphs.
• Calculate the elevation in boiling point when 1.5 g of a non-volatile solute (M = 60 g/mol) is dissolved in 100 g of water (K_b = 0.52 K kg/mol).
• What are colligative properties? Why does adding a non-volatile solute lower the vapour pressure?
• Calculate the osmotic pressure of a 0.1 M glucose solution at 27°C.
• What is the van't Hoff factor? How is it related to the degree of dissociation?

Electrochemistry

• Write the Nernst equation and calculate the EMF of Zn | Zn²⁺ (0.1 M) || Cu²⁺ (0.01 M) | Cu, given E°_cell = 1.10 V.
• How does molar conductivity vary with concentration for strong and weak electrolytes? Draw the graph.
• State Faraday's laws of electrolysis. Calculate the mass of copper deposited by 0.5 A in 1 hour.
• Explain the working of a hydrogen–oxygen fuel cell.
• Distinguish primary and secondary cells, with one example of each.

Chemical Kinetics

• Derive the integrated rate equation for a first-order reaction.
• A first-order reaction has k = 1.15 × 10⁻³ s⁻¹. Find t½ and the time for 90% completion.
• Distinguish order and molecularity of a reaction.
• Use the Arrhenius equation to explain how temperature affects the rate. What is activation energy?

Inorganic Chemistry

d- and f-Block Elements

• Why are most transition metal compounds coloured? Why are Zn²⁺ compounds colourless?
• Give reasons: (a) Zn is not regarded as a transition element; (b) Cr has the configuration [Ar] 3d⁵ 4s¹; (c) transition metals show variable oxidation states.
• What is lanthanoid contraction? What are its consequences?
• Describe the preparation and properties of KMnO₄ and K₂Cr₂O₇.
• Calculate the spin-only magnetic moment of Fe²⁺ (Z = 26).

Coordination Compounds

• Write IUPAC names: [Co(NH₃)₅Cl]Cl₂, K₃[Fe(CN)₆], [Pt(NH₃)₂Cl₂], [CoCl₂(en)₂]⁺.
• Explain crystal field splitting in octahedral complexes. What is Δ_o?
• Draw the cis and trans isomers of [Pt(NH₃)₂Cl₂].
• What is the spectrochemical series? How does it explain the colour of complexes?
• State the main postulates of Werner's theory.

Organic Chemistry

Haloalkanes and Haloarenes

• Explain the S_N1 and S_N2 mechanisms. Which is faster for a primary and for a tertiary halide?
• Why is the C–Cl bond in chlorobenzene shorter than in chloroethane?
• Convert: (a) chlorobenzene to biphenyl; (b) 2-bromopropane to 1-bromopropane.

Alcohols, Phenols and Ethers

• Distinguish: (a) primary, secondary and tertiary alcohols; (b) methanol and ethanol; (c) phenol and ethanol.
• Explain Kolbe's reaction and the Reimer–Tiemann reaction with equations.
• Explain Williamson ether synthesis. Why is a primary alkyl halide preferred?

Aldehydes, Ketones and Carboxylic Acids

• Explain aldol condensation and the Cannizzaro reaction with examples.
• Distinguish an aldehyde from a ketone (Tollens' and Fehling's tests).
• Arrange HCHO, CH₃CHO and (CH₃)₂CO in increasing reactivity towards nucleophilic addition, with reasons.
• Convert: (a) ethanal to 3-hydroxybutanal; (b) benzoic acid to benzaldehyde.

Amines

• Explain Hofmann bromamide degradation and Gabriel phthalimide synthesis with equations.
• Arrange aniline, methylamine, dimethylamine and ammonia in increasing basic strength (in aqueous solution), with reasons.
• What is diazotisation? Write two reactions of benzenediazonium chloride.
• Why is aniline less basic than methylamine?

Biomolecules

• What are reducing and non-reducing sugars? Give one example of each.
• Distinguish: (a) DNA and RNA; (b) starch and cellulose; (c) globular and fibrous proteins.
• What happens when a protein is denatured? Give an example.

For more practice, see our CBSE Class 12 Chemistry important questions pages and the Class 12 Chemistry formula sheet.

Chapter marks from the CBSE Class XII Chemistry syllabus 2026-27 (cbseacademic.nic.in). These are practice questions of common types, not predictions — questions can come from any part of the syllabus.