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

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

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

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

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

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

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

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

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.