CBSE Class 12 Board Exams 2026: Key Chemistry Competency-Based Questions to Practice

The Chemistry paper for the CBSE Class 12 Board Exams 2026 is known for its high difficulty level and requires strong conceptual clarity. A solid understanding of fundamentals not only helps students score well in the CBSE Board Exams 2026 but also plays an important role in competitive exams such as JEE, NEET, and various state-level entrance tests.

Students are advised to revise the full syllabus thoroughly and practise the CBSE Competency-Based Questions for practice released by the board in its official booklet. These questions are designed to reflect the pattern and difficulty level expected in the upcoming examination. Those appearing for the 2026 board exams must attempt every question in a systematic manner, check their answers using the attached key, and work on areas that require more attention. If any chapter still feels unclear, students should seek guidance from teachers and revise the concepts again.

The Class 12 Chemistry exam will be conducted on February 28, from 10:30 AM to 1:30 PM.

Competency-Based Practice Questions for CBSE Class 12 Chemistry

(Aligned with NCERT and built to test application, accuracy, and clarity)

The booklet released by CBSE includes both free-response and multiple-choice questions. Every question has been reviewed for conceptual accuracy and relevance to curriculum learning outcomes. Below are several key questions students should solve while preparing for the upcoming exam.

Solid State – Questions

Q1 — Assertion/Reason

Assertion (A): Compounds with a small cation-to-anion radius ratio and low dielectric constant tend to show Frenkel defects.
Reason (R): A Frenkel defect does not disturb the charge balance of the crystal.

Choose the correct option:
A. A and R are both correct, and R explains A.
B. A and R are both correct, but R does not explain A.
C. A is correct, but R is incorrect.

Q2 — Correct Statements

Identify the correct statements:

(i) Replacing 18% of Fe²⁺ ions with Fe³⁺ results in a non-stoichiometric compound of formula Fe₀.₉₄O.
(ii) Conductivity of intrinsic and extrinsic semiconductors increases with temperature.
(iii) Among common crystal structures, BCC has the highest packing density.

A. (i) and (iii)
B. (ii) and (iii)
C. Only (i)
D. (i) and (ii)

Surface Chemistry – Questions

Q3- Which statement is correct?

(i) Under high temperature and pressure, physical adsorption may convert to chemisorption, and the gas may not be released easily.
(ii) A colloidal solution freezes at a lower temperature than a true solution containing the same amount of solute.

A. Only (i)
B. Only (ii)
C. Both (i) and (ii)
D. (i), (ii), and (iii)

Q4 — Freundlich Isotherm

Which statements are correct?

(i) Amount adsorbed increases in proportion to constant kkk.
(ii) In some situations, adsorption may show no dependence on pressure.
(iii) Adsorption varies directly with 1/n1/n1/n.

A. Only (ii)
B. (ii) and (iii)
C. (i) and (iii)
D. All — (i), (ii), and (iii)

Chemical Kinetics – Questions

Q5 — Haber Process

Iron is used as the catalyst and molybdenum as the promoter in the Haber process.

Which statement is correct?
A. Iron lowers activation energy; molybdenum improves catalyst efficiency.
B. Iron affects the equilibrium constant; molybdenum changes Gibbs energy.
C. Iron alters enthalpy; molybdenum influences equilibrium.
D. Both iron and molybdenum affect Gibbs energy.

Q6 — Reaction Rate

Which of the following increases the rate of reaction?

P) Increasing temperature
Q) Increasing product concentration
R) Adding a catalyst
S) Increasing reactant concentration

A. Q and S
B. P and Q
C. P, R, and S
D. All — P, Q, R, and S

Aldehydes, Ketones & Carboxylic Acids – Subjective Questions

Q7 — Separation Method

A mixture contains two insoluble powders: an aldehyde and an alkane. Describe a method to separate them using a chemical property specific to aldehydes.

Q8 — Isomers of C₃H₆O

A compound with formula C₃H₆O contains a ketone group. Draw the structures of two other compounds with the same molecular formula but containing a different oxygen-based functional group.

Structure & Properties – Subjective Questions

Q9 — Graphite vs Diamond

Explain why graphite conducts electricity and acts as a lubricant, while diamond is hard and non-conductive, based on their structures and bonding.

Q10 — Unit Cell Calculation

Given:
• NaCl unit cell edge length: 563.1 pm
• Density: 2.17 × 10³ kg/m³
• Atomic masses: Na = 22.99, Cl = 35.45

Calculate Z, the number of formula units present in the unit cell.

These competency-based questions are important for students preparing for the upcoming CBSE Class 12 Board Exams 2026. They offer clarity on the type of application-driven problems expected in the paper and form an essential part of CBSE exam-related top news and academic updates for students.