Class 12 ChemistryImportant Questions for Board Exams 2025-26
25
Total Questions
16
Long Answer
9
Short Answer
The Solid State
2 questionsCalculate the packing efficiency of a face-centred cubic unit cell.
What are Frenkel and Schottky defects? In which type of ionic solids does each occur?
Solutions
2 questionsWhat is osmosis? Derive the expression for osmotic pressure. How is it used to determine molecular mass?
18g of glucose (C₆H₁₂O₆) is dissolved in 1kg of water. Calculate the freezing point depression (Kf = 1.86 K kg/mol).
Electrochemistry
1 questionsDefine conductivity and molar conductivity. How does molar conductivity vary with concentration for strong and weak electrolytes?
Chemical Kinetics
1 questionsWhat is the difference between order and molecularity of a reaction? Derive the integrated rate equation for a first order reaction.
Surface Chemistry
2 questionsWhat is adsorption? Distinguish between physisorption and chemisorption.
What is the Tyndall effect? Give one example.
General Principles of Extraction of Elements
2 questionsWhat is the Ellingham diagram? How is it useful in the extraction of metals?
Describe the froth flotation method for concentration of sulphide ores.
The p-Block Elements
2 questionsDescribe the industrial preparation of sulphuric acid by the Contact process.
Why does fluorine not show positive oxidation state unlike other halogens?
The d and f Block Elements
2 questionsExplain why transition elements show variable oxidation states. Give examples.
What is lanthanoid contraction? What are its consequences?
Coordination Compounds
2 questionsWrite the IUPAC name and draw the structure of [Co(NH₃)₄Cl₂]Cl.
Using VBT, explain the hybridisation and geometry of [Ni(CN)₄]²⁻.
Haloalkanes and Haloarenes
1 questionsExplain SN1 and SN2 reactions with examples. What factors favour each?
Alcohols, Phenols and Ethers
2 questionsWhy is phenol more acidic than ethanol? Explain in terms of structure.
How is ethanol prepared industrially?
Aldehydes, Ketones and Carboxylic Acids
2 questionsWrite the mechanism of aldol condensation.
Explain why aldehydes are more reactive than ketones in nucleophilic addition reactions.
Amines
2 questionsArrange in order of basicity: primary, secondary, tertiary amine (in water). Justify.
How are diazonium salts prepared? Give two uses in synthesis.
Biomolecules
2 questionsWhat are reducing sugars? Is sucrose a reducing sugar? Why?
Describe the four levels of protein structure.
Frequently Asked Questions
Which are the most important questions in Class 12 Chemistry for CBSE board exam?
All 25 questions listed here are selected based on CBSE board exam frequency and marks weightage. Prioritise long-answer (5-mark) questions first — 16 questions here — as they carry the most marks. Short-answer questions (9 here) are next. Together they cover the questions most likely to appear.
Is it enough to study only important questions for CBSE Class 12 Chemistry?
Practising these 25 important questions gets you to 70–75% marks. For 85%+, also read chapter summaries and attempt at least one full sample paper under timed conditions. Use these important questions as your minimum baseline, not your ceiling.
How should I write answers in CBSE Class 12 Chemistry board exam?
For 1-mark questions: one direct sentence — no elaboration needed. For 3-mark questions: 3 clearly numbered points, each 1–2 lines. For 5-mark questions: brief intro + 4–5 numbered points with subject-specific keywords + 1-line conclusion. CBSE examiners look for keywords in marking schemes — structure your answers around them.
How many questions come from each chapter in Class 12 Chemistry CBSE board exam?
CBSE doesn't publish a fixed chapter-wise distribution, but chapters with more important questions listed here have historically appeared more frequently in board papers. Focus extra time on chapters with 5 or more questions — those chapters consistently carry high marks.