Top Questions to Expect in CBSE Class 12 Chemistry Board Exam 2025

CBSE Class 12 Chemistry board examination is one of the important exams for students and good preparation can go on to make a huge difference with regard to marks obtained. The CBSE has already announced the Class 12 Date sheet 2025 and the timer has started. Besides, the CBSE has also provided Sample papers for Class 12 for the session 2024-25 to let them understand the type of questions they are asked in the examination apart from the marking scheme.

This Story also Contains

1. Exam Pattern for CBSE Class 12 Chemistry Exam
2. Questions to expect in CBSE Class 12 Chemistry Board Exam 2025
3. Important Topics for CBSE Class 12 Chemistry Exam 2025
4. Tips for Scoring High Marks in CBSE Class 12 Board Exams 2025

Chemistry is such a subject that is likely to contain questions on theory as well as practical therefore one has to plan how to prepare it. From simple numerical problems of Physical Chemistry to reactions of Organic Chemistry and Inorganic Chemistry all are significant parts. For example, learning those questions that are expected in the exams can prepare you better and boost your morale during the examination.

In this article, we have created a list of questions that are likely to be asked in the following CBSE Class 12 2024-25 Chemistry Board Exams. The questions of the following list are prepared making use of the latest CBSE syllabus, sample papers, and trends to facilitate your best preparation.

Exam Pattern for CBSE Class 12 Chemistry Exam

The table below shows the exam pattern and the marking scheme for CBSE Class 12 exams.

Questions to expect in CBSE Class 12 Chemistry Board Exam 2025

Question 1:

Define the term isometric system in crystal structures. List the types of Bravais lattices that belong to this system.

Question 2:

Explain the concept of packing efficiency and calculate it for a simple cubic structure.

Question 3:

What is Raoult’s Law? Derive the expression for the relative lowering of vapor pressure for a solution.

Question 4:

Define osmotic pressure and derive its relation with molarity for dilute solutions.

Question 5:

Calculate the standard cell potential for the following galvanic cell at 25°C:

$$
\mathrm{Zn}(\mathrm{~s})\left|\mathrm{Zn}^{2+}(1 \mathrm{M})\right|\left|\mathrm{Cu}^{2+}(1 \mathrm{M})\right| \mathrm{Cu}(\mathrm{~s})
$$

Given standard reduction potentials:
- $\mathrm{Cu}^{2+}+2 e^{-} \rightarrow \mathrm{Cu}(\mathrm{s}), E^{\circ}=+0.34 \mathrm{~V}$
- $\mathrm{Zn}^{2+}+2 e^{-} \rightarrow \mathrm{Zn}(\mathrm{s}), E^{\circ}=-0.76 \mathrm{~V}$

Question 6:

Explain the difference between galvanic cells and electrolytic cells with suitable examples.

Question 7:

A first-order reaction has a rate constant $k=0.693 \mathrm{~s}^{-1}$. Calculate the half-life of the reaction.

Question 8:

Describe the Arrhenius Equation and explain how it relates temperature to the rate constant of a reaction.

Question 9:

Define adsorption and absorption. Highlight the differences between them.

Question 10:

Explain the Langmuir Adsorption Isotherm and its significance in surface chemistry.

Question 11:

Compare the acidity of HClO₄, HClO₃, HClO₂, and HClO.

Question 12:

Why do group 15 elements exhibit the -III oxidation state? Provide examples.

Question 13:

Define coordination number. What is the coordination number of Chromium in [Cr(NH₃)₆]Cl₃?

Question 14:

What is the Chelate Effect? Explain its importance with an example.

Question 15:

Describe the SN2 mechanism for the reaction of 1-Bromopropane with Sodium Hydroxide.

Question 16:

Predict whether the following compounds will undergo SN1, SN2, or neither reaction with NaOH: a) 2-Bromopropane
b) 1-Bromopropane

Question 17:

Why are phenols more acidic than alcohols? Support your answer with structural reasoning.

Question 18:

Explain why tert-Butyl alcohol does not undergo dehydration as readily as sec-Butyl alcohol.

Question 19:

Differentiate between addition polymerization and condensation polymerization with suitable examples.

Question 20:

What are copolymers? Give an example and explain its significance.

Question 21:

Describe the principles and steps involved in the electrolytic reduction of Aluminum oxide to obtain aluminum metal.

Question 22:

Explain the zone refining method used for the purification of metals. Mention its advantages.

Question 23:

Explain the difference between hydrogen bonding in alcohols and carboxylic acids.

Question 24:

Describe the Tollens’ Test and its significance in distinguishing aldehydes from ketones.

Question 25:

Why do transition metals often form colored compounds? Illustrate with an example.

Question 26:

Explain why iron is considered a transition metal. Support your answer with its electronic configuration.

Question 27:

Outline the structure of DNA and explain its role in heredity.

Question 28:

What is the role of ribosomes in a cell?

Question 29:

Explain the role of antacids in neutralizing gastric acidity. Provide the chemical equation for the reaction with calcium carbonate.

Question 30:

How does soda water (carbonated water) become acidic? Write the chemical equation for the dissolution of CO₂ in water.

Question 31:

What is ligand substitution in coordination complexes? Illustrate with an example involving [Co(NH₃)₆]^{3+}.

Question 32:

Predict the geometry of the complex [Co(NH₃)₅Cl]Cl₂ and state the oxidation state of cobalt.

Question 33:

Compare the oxidation states of nitrogen and phosphorus in their respective hydrides.

Question 34:

Explain why group 15 elements form VSEPR shapes different from their lighter congeners using phosphorus pentachloride (PCl₅) as an example.

Question 35:

What is the role of ATP (Adenosine Triphosphate) in cellular processes?

Question 36:

Define a polypeptide and explain its role in proteins.

Question 37:

Differentiate between homopolymers and copolymers with examples.

Question 38:

What are thermoplastics and thermosetting polymers? Provide examples of each.

Question 39:

Outline the principles of the Hall-Héroult process for the extraction of aluminum.

Question 40:

Describe the Dow Process for the manufacture of sulfuric acid.

Question 41:

Predict the major product when butan-2-one reacts with hydrogen in the presence of NaBH₄.

Question 42:

Why are ketones generally less reactive towards nucleophilic addition than aldehydes?

Question 43:

Discuss the magnetic properties of the MnO₄⁻ ion.

Question 44:

Explain the color of the tetraamminecopper(II) sulfate solution.

Question 45:

What are carbohydrates and what is their primary role in living organisms?

Question 46:

What is the difference between DNA and RNA in terms of structure and function?

Question 47:

Explain how antacid neutralizes excess stomach acid. Provide a balanced chemical equation using calcium carbonate as the antacid.

Question 48:

How does soda water restore the lustre of silverware?

Question 49:

Describe the principles of the Kroll Process for the production of titanium.

Question 50:

Explain the zone refining method used for the purification of silicon. Mention its advantages.

Important Topics for CBSE Class 12 Chemistry Exam 2025

Here is a curated list of important topics, based on the analysis of repeated questions and overall syllabus relevance:

1. Physical Chemistry

• Electrochemistry:

  • Nernst Equation and its applications (EMF calculations).
  • Conductivity, molar conductivity, and cell constant.
  • Factors affecting electrolytic conductance.
  • Galvanic cell and electrolytic cells.
• Chemical Kinetics:
  • Integrated rate laws for zero, first, and second-order reactions.
  • Arrhenius equation and activation energy.
  • Calculation of half-life (t₁/₂) for first-order reactions.
  • Graphical representations of reaction order.
• Solid State:
  • Crystal defects: Schottky and Frenkel.
  • Calculations involving unit cell parameters.
  • Packing efficiency and density of crystals.

2. Organic Chemistry

• Aldehydes and Ketones:
  • Mechanisms of Aldol condensation and Cannizzaro reactions.
  • Reactions involving Grignard reagents.
  • Distinguishing tests (e.g., Tollen's and Fehling's test).
• Amines:
  • Hinsberg test for distinguishing primary, secondary, and tertiary amines.
  • Acylation and alkylation reactions.
  • Comparison of basicity (pKb values) in alkyl and aromatic amines.
• Carboxylic Acids:
  • Acid strength trends based on substituents.
  • Conversion reactions (e.g., carboxylic acid to aniline or aldehyde).
• Coordination Compounds:
  • Writing IUPAC names of complexes.
  • Hybridization, geometry, and magnetic properties.
  • Stability and colour of complexes based on ligands.

3. Inorganic Chemistry

• Transition Elements:
  • Catalytic properties of transition metals.
  • Comparison of oxidation states and their applications.
  • Enthalpies of atomization and stability of half-filled and fully-filled orbitals.
• d- and f-Block Elements:
  • Properties of lanthanides and actinides.
  • Colour, magnetic properties, and formation of complexes.
• P-Block Elements:
  • Trends in acidity, basicity, and bond strength.
  • Oxides and oxyacids of nitrogen, phosphorus, and sulfur.

4. Case-Based Topics

• Electrochemistry: Practical applications like fuel cells and batteries.
• Chemical Kinetics: Real-world scenarios involving reaction rates.
• Organic Chemistry: Multi-step synthesis and conversions.

5. Numerical Problems

• EMF calculations using the Nernst equation.
• Determining reaction order and rate constant.
• Calculations involving unit cell density and conductivity.
• Gibbs free energy and its relation to spontaneity in electrochemical cells.

Tips for Scoring High Marks in CBSE Class 12 Board Exams 2025

• Know the syllabus and avoid concentrating on chapters with less marks.
• Prepare from NCERT books as most of the questions are framed from them.
• Ensure that extra time is divided between the chapters with high weightage.
• Solve sample question papers and papers from previous years to familiarize yourself with the question type.
• Practice writing neat and straight-to-the-point answers using diagrams and flow charts.
• Analyze the topics that you have difficulty in answering and practice that properly before appearing in the exams.
• Time management is important during the exam and students should begin by answering easy questions.
• Make sure to leave some time to cross-check your answers at the end of the exam.
• Have a balanced diet, drink enough water, and ensure you take enough rest before exams.
• It is useful to take a break from time to time in order to prevent getting burned with studies.
• Continue to keep a positive attitude and confidence in your preparation do not worry yourself unnecessarily.