ISC Class 12 Chemistry Previous Year Question Papers with Solutions (2020-2026)

CISCE cancelled the 2021 ISC board exams during COVID-19, so there is no 2021 board paper and the table goes from 2022 back to 2020.

ISC Chemistry 2026 question paper: chapter-wise marks

The 2026 theory paper had 21 questions for 70 marks, all compulsory, in four sections. Here is how the marks split by chapter when you count every sub-part:

• Physical chemistry, 25 marks: solutions 9, chemical kinetics 8, electrochemistry 8
• Inorganic chemistry, 14 marks: d- and f-block elements 6, coordination compounds 8
• Aldehydes, ketones and carboxylic acids: 9 marks
• Biomolecules: 4 marks
• Haloalkanes and haloarenes, alcohols, phenols, ethers and amines: 18 marks together. Many of these questions mix two chapters in one conversion, so we have not split them.
• Section A (14 marks): four fill-in-the-blanks, seven MCQs (two of them assertion-reason) and a three-part case on Kohlrausch's law. Section B: ten 2-mark questions. Section C: seven 3-mark questions. Section D: three 5-mark questions. One question in each of Sections B, C and D had an internal choice.

Source: CISCE ISC 2026 Chemistry Paper 1 (Theory), Gradehunt analysis. Q9 is counted under carbonyl compounds, although its OR option starts from an alcohol.

Organic chemistry carried 31 of the 70 marks, close to half the paper. Twelve of those marks came from questions that asked for nothing but equations: two conversions in Q5, diazotisation and Sandmeyer's reaction in Q7, two more conversions in Q11, three in Q12 and three reactions in Q15. If you can write those reactions from memory, with reagents and conditions, they are the quickest marks on the paper.

Numericals were spread across the physical chapters. They included freezing point depression in Q3 and Q19, osmotic pressure in Q19, the time for 90% completion of a first-order reaction in Q8, activation energy in Q16, Gibbs energy of a cell in Q6 and molar conductivity in Q1(C) and Q17.

How long to spend on each ISC Chemistry section

Three hours for 70 marks gives you about 2 minutes 35 seconds a mark. That is roughly 36 minutes for Section A, 51 minutes for Section B, 54 minutes for Section C and 39 minutes for Section D, which leaves no spare time. Most students gain a few minutes on the one-mark questions and on equation-only questions, so bank that time for the 5-mark numericals.

Where ISC Chemistry students lost marks in 2025

CISCE's Analysis of Pupil Performance for 2025 reports 51,505 ISC Chemistry candidates, an average of 68 out of 100, a highest score of 100 and a lowest of 2. The examiners listed these among the topics candidates found difficult or confused:

• Chemical tests to tell two organic compounds apart, and identifying an unknown organic compound
• Balancing reactions of KMnO4 and K2Cr2O7
• Numericals on the van't Hoff factor, osmotic pressure, molecular mass and vapour pressure
• Rate constant and order of reaction numericals, and Nernst equation numericals
• Gibbs energy and cell emf in terms of spontaneity
• Naming, isomerism and hybridisation of coordination compounds

The 2026 paper went straight back to most of them. Q9 asked for tests to distinguish acetaldehyde from acetone, Q13 asked you to complete and balance the KMnO4 and K2Cr2O7 reactions, Q19 had an osmotic pressure sum and Q21 tested hybridisation, magnetic behaviour and isomerism of complexes.

The same report gives advice that matches how marks are awarded. For numericals, write the formula, then the substitution, then the answer with its unit. Write organic equations complete and balanced, with reagents, conditions and catalysts. Use the key word the question is looking for in reasoning answers, and write IUPAC names carefully.

ISC Chemistry 2027: what we know so far

• CISCE's circular of 9 October 2026 lists Chemistry Paper 1 among the ISC subjects with a 2027 specimen paper and answer key, published on cisce.org.
• The same circular says questions that test apply, analyse, evaluate and create will carry about 50% of the marks in the 2027 exams, and that the topic weightage in the syllabus will be strictly followed.
• Compare the 2027 specimen's sections with the 2026 layout above before you start full mocks, and expect apply-and-analyse questions to take a bigger share than in the older papers.

How to practise with these papers

• Write the 2026 paper first as a timed three-hour test and check it against the solution.
• Do 2025, 2024 and 2023 next. Keep a running list of every reaction and named reaction you got wrong.
• Use the two 2022 semester papers for chapter practice, since each covered only part of the syllabus. The 2020 paper is a full board paper for one more timed test.
• Before the exam, rewrite your reaction list from memory until you can do it without gaps.

For the board questions from 2016 to 2026 worked out step by step and sorted chapter by chapter, get Gradehunt's ISC Class 12 10 Years Solved Papers (PYQ).

The chapter list is in our ISC Class 12 Chemistry syllabus guide. Solved past papers are also up for ISC Physics and ISC Biology.