CBSE Class 12 Electrochemistry PYQs Analysis (2021-2025)

Based on detailed analysis of last 5 years' papers. Perfect for 2026 Boards prep!

Key Trends

Weightage Breakdown: Typically, 2-3 MCQs/assertion-reason (1 mark each), 1-2 short answers/numericals (2-3 marks), and occasionally a case-based question (4 marks).
Repeated Topics: Nernst equation, Faraday's laws, molar conductivity, batteries, standard electrode potential, ΔG and Ecell.
Difficulty: Medium to high; numerics are common.
Changes: MCQ-heavy in 2021, more applications in later years.

Most Important and Repeated Questions

Question Example	Type/Marks	Years Repeated	Notes
Assertion: Molar conductivity of CH3COOH can be calculated using Kohlrausch's law. Reason: At infinite dilution, each ion contributes independently to conductivity.	Assertion-Reason (1 mark)	2023, 2024, 2025	Repeated 3x; both true, reason explains assertion.
The conductivity of 0.001 M CH3COOH is 4 × 10^{-5} S/cm. Calculate degree of dissociation if Λ°m = 390 S cm²/mol.	Numerical (2 marks)	2022, 2023, 2025	Repeated 3x; α = Λm / Λ°m.
Write the Nernst equation for the cell Zn \| Zn²⁺ (0.1 M) \|\| Cu²⁺ (0.01 M) \| Cu. Calculate Ecell if E°cell = 1.1 V.	Short Answer/Numerical (3 marks)	2021 Term 2, 2024, 2025	Repeated 3x; E = E° - (0.059/2) log (0.1 / 0.01).
Explain Faraday's first and second laws of electrolysis. Calculate mass of Ag deposited if 2 F electricity is passed through AgNO3. (At. mass Ag = 108)	Long Answer (3 marks)	2021 Term 1, 2022, 2024	Repeated 3x; m = (108 * 2) / 1 = 216 g.
Which is a stronger reducing agent: Cr²⁺ or Fe²⁺? Explain using E° values (E° Cr³⁺/Cr²⁺ = -0.41 V, E° Fe³⁺/Fe²⁺ = 0.77 V).	Reasoning (2 marks)	2023, 2025	Repeated 2x; Cr²⁺ (more negative E°).
Draw graph of Λm vs √c for strong and weak electrolytes. Explain the effect of dilution.	Short Answer (2 marks)	2022, 2024	Repeated 2x; Strong: straight line, weak: curve.
Describe fuel cell with diagram. Give advantages and equation for H2-O2 cell.	Case-Based (4 marks)	2023, 2025	Repeated 2x; 2H2 + O2 → 2H2O, E = 1.23 V.
Calculate ΔG° for the cell with E°cell = 0.34 V and n = 2. Is the reaction spontaneous?	Numerical (2 marks)	2021 Term 2, 2023	Repeated 2x; ΔG° = -nFE° (negative, spontaneous).
MCQ: The quantity of charge required to deposit 1 mol Al from AlCl3 is: (a) 1 F (b) 3 F (c) 96500 C (d) 3 × 96500 C	MCQ (1 mark)	2024, 2025	Repeated 2x; Answer (b).
Explain corrosion as electrochemical process. How can it be prevented?	Short Answer (3 marks)	2022, 2023	Repeated 2x; Anode: Fe → Fe²⁺, cathode: O2 + H2O → OH⁻.

Best Format for Preparation and Answering

Study Format: Use tables for formulas. Practice 10 PYQs per topic. Focus on numerics.
Answer Format: Show formula, substitution, unit for numerics. Draw labeled diagrams.
Tips: Revise Kohlrausch's law. Time management: 15 mins for chapter.

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