ISC 2025 Chemistry Improvement Examination Question Paper for Class 12

About this paper

This is the ISC Class 12 Chemistry Paper 1 (Theory) from the 2025 improvement examination, code 862A-IE. It carries 70 marks over three hours, with fifteen minutes to read the paper, and has 21 compulsory questions in four sections. Section A is worth 14 marks and ends with a passage on the Arrhenius equation, including the activation energy when a rate triples between 30°C and 60°C. Ten questions carry two marks, seven carry three marks and three carry five marks, with an internal choice in one question each in Sections B, C and D. Among the questions are a gold-electroplating calculation, a carbon-14 dating problem with a half-life of 5730 years, and a passage on Raoult's law. Constants are printed for the numerical work. This copy has the questions only.

Exam

ISC Class 12

Subject

Chemistry

Year

2025

Paper code

862A-IE

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

21

Pages

12

Answers included

No, questions only

Paper pattern

• Section A

  14 marks

  Question 1 with 14 one-mark sub-parts: four fill-in-the-blanks, seven multiple-choice items (two assertion–reason) and three questions on an Arrhenius-equation passage

• Section B

  20 marks

  Questions 2–11, two marks each; internal choice in one question

• Section C

  21 marks

  Questions 12–18, three marks each; internal choice in one question

• Section D

  15 marks

  Questions 19–21, five marks each, including a passage on Raoult's law; internal choice in one question

Topics covered

• Electrochemistry
• Chemical kinetics
• Solutions and colligative properties
• Coordination compounds
• d- and f-block elements
• Haloalkanes and haloarenes
• Alcohols, phenols and ethers
• Aldehydes and ketones
• Biomolecules
• Radioactive decay

Questions from this paper

1. Calculate the charge in coulombs needed to electroplate 1.0 g of gold by the reaction Au3+ + 3e− → Au. (Atomic weight of Au = 197 g mol−1.)
2. The half-life of radioactive carbon-14 is 5730 years. An ancient wood sample has only 80% of the C-14 activity of a living plant. Estimate the age of the sample.
3. Write chemical equations to convert chlorobenzene to biphenyl and chloroform to acetylene.
4. [Co(NH3)6]3+ is an inner orbital complex, whereas [CoF6]3− is an outer orbital complex. Why? (Atomic number of Co = 27.)
5. What is observed when D-glucose is treated with bromine water? Write the chemical reaction.
6. Calculate the vapour pressure of a solution containing 2 moles of glucose in 900 g of water if the vapour pressure of pure water is 4.60 mm of Hg.