CBSE Class 12 Physical and Inorganic Chemistry Board Exam Analysis (PYQs 2020-2025)

Building on the organic chemistry overview, this provides a more detailed chapter-wise breakdown for Physical Chemistry in CBSE Class 12 (Units 1-4 from NCERT). The analysis is derived from trends in previous year question papers (PYQs) from 2020-2025, including the 2025 paper which was rated moderate overall, with physical sections emphasizing numericals and graphs. Physical Chemistry typically carries 20-25 marks (28-35% of the paper), focusing on calculations, derivations, and conceptual applications. Questions include MCQs (1 mark), numericals (2-3 marks), graphs (3 marks), and case-based (4 marks).

Repetition is high for numerical problems (e.g., in electrochemistry and kinetics, appearing in 5-6/6 years). Difficulty in 2025 was moderate for physical (per student feedback), with emphasis on application-based questions. Trends post-2022 include more assertion-reason and graph interpretation. In 2025, physical was ~25 marks, direct from NCERT, with predictable topics like rate laws and colligative properties.

Unit 1: Solutions (5-7 Marks Total, High Repetition: 5/6 Years)

Subtopics Covered

Types of solutions, concentration units (molality, molarity, mole fraction), Raoult's law, ideal/non-ideal solutions, colligative properties (vapour pressure lowering, boiling point elevation, freezing point depression, osmotic pressure), van't Hoff factor, abnormal molar masses, Henry's law.

Marks Distribution and Question Types

• 1 mark: MCQs on concentration units or ideal vs non-ideal.
• 2-3 marks: Numericals on colligative properties or Raoult's law.
• 4-5 marks: Case-based on real-life applications (e.g., antifreeze).

Repetition Frequency

High; colligative numericals and van't Hoff repeat annually. In 2025, 7 marks, with moderate numericals.

Named Reactions

None; focus on laws (Raoult's, Henry's).

Reasoning-Type Questions

Common (80% papers); e.g., "Why does molarity change with temperature?" (volume dependence); "Explain abnormal colligative properties in electrolytes" (dissociation). Repetition: 5/6 years.

Mechanisms Asked

Rare; derivations of colligative formulas (e.g., ΔTb = Kb m i) in 3/6 years.

Most Important Questions (from Analysis)

1. Calculate the boiling point of a solution with given molality and Kb (3 marks, repeated 2020-2025).
2. Explain deviation from Raoult's law with examples (2 marks, annual).
3. Find van't Hoff factor for a dissociated electrolyte (2 marks, 2021-2025).
4. Henry's law application: Solubility of gas in liquid (2 marks, 2022-2024).
5. Case-based: Osmotic pressure in blood cells (4 marks, 2023-2025).

Unit 2: Electrochemistry (6-8 Marks Total, Very High Repetition: 6/6 Years)

Subtopics Covered

Redox reactions, conductance (specific, molar), Kohlrausch's law, electrochemical cells (galvanic, electrolytic), Nernst equation, EMF, Faraday's laws, batteries, corrosion, fuel cells.

Marks Distribution and Question Types

• 1-2 marks: MCQs on cell types or conductance.
• 3 marks: Numericals on Nernst or Faraday.
• 5 marks: Derivations or case-based (e.g., battery efficiency).

Repetition Frequency

Highest; Nernst equation and Faraday's laws in every paper. In 2025, 8 marks, numerical-heavy.

Named Reactions

None; electrochemical series applications.

Reasoning-Type Questions

Frequent; e.g., "Why is conductivity lower in weak electrolytes?" (partial dissociation); "Explain corrosion prevention" (cathodic protection). 6/6 years.

Mechanisms Asked

Electrode reactions (e.g., Daniel cell); Nernst derivation. Repeated annually, e.g., 2025 Nernst.

Most Important Questions

1. Calculate cell potential using Nernst equation (3 marks, repeated 2020-2025).
2. Apply Faraday's first law to find mass deposited (3 marks, annual).
3. Distinguish galvanic vs electrolytic cells (2 marks, 6/6 years).
4. Kohlrausch's law: Molar conductance calculation (2 marks, 2021-2025).
5. Case-based: Fuel cell working (4 marks, 2022-2025).

Unit 3: Chemical Kinetics (5-7 Marks Total, High Repetition: 5/6 Years)

Subtopics Covered

Rate of reaction, rate laws, order/molecularity, integrated rate equations, half-life, Arrhenius equation, activation energy, collision theory, catalysis.

Marks Distribution and Question Types

• 1 mark: MCQs on order vs molecularity.
• 2-3 marks: Numericals on half-life or rate constants.
• 4 marks: Graph-based (e.g., zero-order plot).

Repetition Frequency

High; integrated equations and graphs repeat often. In 2025, 7 marks, graph-focused.

Named Reactions

None; focus on equations (Arrhenius).

Reasoning-Type Questions

Common; e.g., "Why is molecularity not fractional?" (elementary steps); "Effect of catalyst on activation energy" (lowers Ea). 5/6 years.

Mechanisms Asked

Derivation of integrated rate laws (zero/first/second order). Arrow not needed, but steps; repeated 5/6 years, e.g., 2023-2025 first-order.

Most Important Questions

1. Derive integrated rate law for first-order reaction (3 marks, repeated 2021-2025).
2. Calculate activation energy from Arrhenius plot (3 marks, annual).
3. Identify order from units of k (2 marks, 2020-2024).
4. Half-life numerical for zero-order (2 marks, 2022-2025).
5. Case-based: Enzyme catalysis (4 marks, 2023-2025).

Unit 4: Surface Chemistry (4-5 Marks Total, Medium Repetition: 4/6 Years)

Subtopics Covered

Adsorption (physisorption, chemisorption), isotherms (Freundlich, Langmuir), catalysis (homogeneous/heterogeneous), colloids (types, preparation, properties like Tyndall, electrophoresis), emulsions, micelles.

Marks Distribution and Question Types

• 1-2 marks: MCQs on adsorption types.
• 3 marks: Reasoning or isotherms.
• 4 marks: Case-based (e.g., detergents).

Repetition Frequency

Medium; adsorption and colloids repeat. In 2025, 5 marks, conceptual.

Named Reactions

None; isotherms as models.

Reasoning-Type Questions

High; e.g., "Why chemisorption increases with temperature initially?" (activation); "Explain coagulation" (charge neutralization). 4/6 years.

Mechanisms Asked

Adsorption mechanisms (multilayer in Freundlich); rare, 3/6 years.

Most Important Questions

1. Explain Freundlich isotherm with equation (3 marks, repeated 2020-2024).
2. Distinguish physisorption vs chemisorption (2 marks, 4/6 years).
3. Properties of colloids: Tyndall effect (2 marks, 2022-2025).
4. Role of enzymes in catalysis (2 marks, 2021-2023).
5. Case-based: Micelle formation in soaps (4 marks, 2024-2025).

Overall Insights for 2026 Prep

Emphasize numericals (70% of physical marks) from NCERT examples. High-repetition in electrochemistry/kinetics can fetch 12+ marks. Practice graphs and derivations. PYQs 2020-2025 show easier numericals in 2025 vs twisted in 2023. Feedback: NCERT + PYQs ensure 90%+ in physical.

Chapter-Wise Detailed Analysis of CBSE Class 12 Inorganic Chemistry Board Exam Questions (Based on PYQs 2020-2025)

This section covers Inorganic Chemistry (Units 5-8 from NCERT). Inorganic typically carries 18-20 marks (25-28% of the paper), with focus on properties, reactions, and reasoning. Questions: MCQs (1 mark), short answers (2-3 marks), and long (5 marks) on extractions or trends.

Repetition high for p-block and coordination (5/6 years). 2025 inorganic was moderate, NCERT-based, ~20 marks, with trends like d-block properties.

Unit 5: General Principles and Processes of Isolation of Elements (3-4 Marks Total, Medium Repetition: 4/6 Years)

Subtopics Covered

Minerals, ores, concentration (froth flotation, magnetic separation), extraction (roasting, calcination, smelting), thermodynamic principles (Ellingham diagram), refining (distillation, electrolysis).

Marks Distribution and Question Types

• 1 mark: MCQs on ore types.
• 2-3 marks: Reasoning on processes.
• 4 marks: Case-based (e.g., aluminum extraction).

Repetition Frequency

Medium; Ellingham and froth flotation repeat. In 2025, 4 marks.

Named Reactions

Hall-Heroult, Bayer's process.

Reasoning-Type Questions

Common; e.g., "Why is carbon used in iron extraction?" (reducing agent); "Explain self-reduction in copper" (Cu2S + O2). 4/6 years.

Mechanisms Asked

Extraction flows (e.g., Fe from hematite); steps with equations, repeated 4/6 years.

Most Important Questions (from Analysis)

1. Describe extraction of iron from hematite (3 marks, repeated 2020-2024).
2. Explain Ellingham diagram for metal oxides (2 marks, 4/6 years).
3. Concentration methods for sulphide ores (2 marks, 2022-2025).
4. Why is zinc extracted by carbon reduction? (2 marks, 2021-2023).
5. Case-based: Electrolytic refining of copper (4 marks, 2024-2025).

Unit 6: The p-Block Elements (6-8 Marks Total, High Repetition: 5/6 Years)

Subtopics Covered

Group 15-18 trends, nitrogen (Haber process), phosphorus (allotropes, PCl3/5), oxygen (ozone, allotropes), sulphur (SO2, H2SO4), halogens (preparation, properties, interhalogen), noble gases (compounds like XeF2).

Marks Distribution and Question Types

• 1-2 marks: MCQs on trends or properties.
• 3 marks: Preparations or reactions.
• 5 marks: Comparative studies.

Repetition Frequency

High; Haber and Contact process annual. In 2025, 8 marks.

Named Reactions

Haber-Bosch, Contact process, Ostwald's.

Reasoning-Type Questions

Frequent; e.g., "Why nitrogen is inert?" (triple bond); "Acidity order of oxyacids" (electronegativity). 5/6 years.

Mechanisms Asked

Reaction mechanisms (e.g., NO in Ostwald); equations with conditions, repeated 5/6 years.

Most Important Questions

1. Describe Haber process for ammonia (3 marks, repeated 2020-2025).
2. Trends in group 17: Reactivity order (2 marks, annual).
3. Preparation of H2SO4 by Contact process (3 marks, 2021-2025).
4. Why phosphorus forms PCl5 but nitrogen PCl3? (2 marks, 2022-2024).
5. Case-based: Ozone layer depletion (4 marks, 2023-2025).

Unit 7: The d- and f-Block Elements (5-6 Marks Total, High Repetition: 5/6 Years)

Subtopics Covered

General properties (variable oxidation, color, magnetism), transition metals (KMnO4, K2Cr2O7 preparations/reactions), lanthanoids/actinoids (contraction, properties).

Marks Distribution and Question Types

• 1 mark: MCQs on oxidation states.
• 2-3 marks: Reasoning on properties.
• 5 marks: Reactions of dichromate/permanganate.

Repetition Frequency

High; KMnO4 reactions repeat. In 2025, 6 marks.

Named Reactions

Preparation of KMnO4, oxidation reactions.

Reasoning-Type Questions

Common; e.g., "Why transition metals form complexes?" (d-orbitals); "Lanthanoid contraction effect" (shielding). 5/6 years.

Mechanisms Asked

Redox reactions (e.g., Cr2O7^2- in acid); balanced equations, repeated 5/6 years.

Most Important Questions

1. Properties of transition metals: Color and magnetism (3 marks, repeated 2021-2025).
2. Preparation and uses of K2Cr2O7 (3 marks, annual).
3. Explain lanthanoid contraction (2 marks, 2020-2024).
4. Oxidation states in d-block (2 marks, 2022-2025).
5. Case-based: Actinoid vs lanthanoid differences (4 marks, 2023-2025).

Unit 8: Coordination Compounds (5-7 Marks Total, Very High Repetition: 6/6 Years)

Subtopics Covered

Werner's theory, nomenclature, isomerism (geometrical, optical, linkage), bonding (VBT, CFT), stability, applications.

Marks Distribution and Question Types

• 1-2 marks: MCQs on isomerism.
• 3 marks: Nomenclature or CFT.
• 5 marks: Isomer examples.

Repetition Frequency

Highest; isomerism in every paper. In 2025, 7 marks.

Named Reactions

None; theories (Werner, VBT).

Reasoning-Type Questions

High; e.g., "Why [Co(NH3)6]^3+ is stable?" (chelate effect); "Splitting in octahedral vs tetrahedral" (CFT). 6/6 years.

Mechanisms Asked

Crystal field splitting diagrams; repeated annually.

Most Important Questions

1. Draw isomers of [Co(en)3]^3+ (3 marks, repeated 2020-2025).
2. Nomenclature of coordination compounds (2 marks, annual).
3. Explain CFT for d4 ion (3 marks, 2021-2025).
4. Distinguish ionization vs hydrate isomerism (2 marks, 2022-2024).
5. Case-based: Color in complexes (4 marks, 2023-2025).

Overall Insights for 2026 Prep

Focus on reactions and trends from NCERT tables. High-repetition in p-block and coordination for 12+ marks. Practice diagrams and equations. PYQs show direct questions in 2025. Feedback: Memorize properties for full marks in inorganic.