Complete Summary and Solutions for Electrochemistry – NCERT Class XII Chemistry Part I, Chapter 2 – Conductance, Kohlrausch's Law, Electrochemical Cells, Fuel Cells, Corrosion
Detailed summary and explanation of Chapter 2 'Electrochemistry' from the NCERT Class XII Chemistry Part I textbook, covering electrical conductance in electrolytic solutions, specific and molar conductance, Kohlrausch's law, electromotive force (EMF) of electrochemical cells, Nernst equation, types of electrodes and cells, fuel cells, corrosion and its prevention, along with solved examples and all NCERT questions and answers.
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Categories: NCERT, Class XII, Chemistry Part I, Chapter 2, Electrochemistry, Conductance, Kohlrausch's Law, EMF, Fuel Cells, Corrosion, Summary, Questions, Answers
Zn anode in ZnSO4, Cu cathode in CuSO4; salt bridge connects; electrons flow Zn to Cu; current opposite; no actual figure, but visualizes redox halves with arrows for flow.
2.2.1 Measurement of Electrode Potential
Standard Hydrogen Electrode (SHE): Pt|H2(1 bar)|H+(1 M); E° = 0 V.
Calculation: Cell emf gives E° for other half (e.g., Cu 0.34 V, Zn -0.76 V).
Tip: Memorize table trends; practice Nernst numericals; compare galvanic/electrolytic.
Project & Group Ideas
Build simple Daniell cell and measure emf.
Debate: Eco-impact of batteries.
Analyze fuel cell future.
Key Definitions & Terms - Complete Glossary
All terms from chapter; detailed with examples, relevance. Expanded: 30+ terms grouped by subtopic; added advanced like "standard electrode potential", "Nernst equation" for depth/easy flashcards.
Electrochemistry
Study of electricity from reactions or vice versa. Ex: Battery conversion. Relevance: Energy tech.
Galvanic Cell
Spontaneous redox to electricity. Ex: Daniell cell. Relevance: Power sources.
Electrolytic Cell
Electricity for non-spontaneous. Ex: Electrolysis. Relevance: Metal production.
Electrode Potential
Difference at interface. Ex: Cu2+/Cu 0.34 V. Relevance: Cell emf.
Standard Electrode Potential (E°)
At 1 M, 298 K, 1 bar vs. SHE. Ex: Zn -0.76 V. Relevance: Reactivity.
Anode
Oxidation site. Ex: Zn in Daniell. Relevance: Electron source.
Cathode
Reduction site. Ex: Cu in Daniell. Relevance: Electron sink.
Salt Bridge
Maintains neutrality. Ex: KCl agar. Relevance: Ion balance.
96487 C/mol. Ex: Charge per mole e-. Relevance: Electrolysis.
Oxidizing Agent
Gains electrons. Ex: F2 (high E°). Relevance: Strength from table.
Reducing Agent
Loses electrons. Ex: Li (low E°). Relevance: Reactivity series.
Tip: Group by type (cells/potentials/equations); examples for recall. Depth: Debates (e.g., sign conventions). Errors: Confuse anode/cathode. Interlinks: To redox (Ch4). Advanced: Inert electrodes. Real-Life: Corrosion prevention. Graphs: Potential series. Coherent: Evidence → Interpretation. For easy learning: Flashcard per term with formula.
60+ Questions & Answers - NCERT Based (Class 12) - From Exercises & Variations
Based on chapter + expansions. Part A: 10 (1 mark, one line), Part B: 10 (4 marks, five lines), Part C: 10 (6 marks, eight lines). Answers point-wise in black text.
Part A: 1 Mark Questions (10 Qs - Short)
1. Define electrochemistry.
1 Mark Answer:
Study of electricity from chemical reactions or vice versa.
2. What is a galvanic cell?
1 Mark Answer:
Device converting chemical to electrical energy spontaneously.
3. Define electrode potential.
1 Mark Answer:
Potential difference at electrode-electrolyte interface.
4. What is SHE?
1 Mark Answer:
Standard hydrogen electrode with E° = 0 V.
5. State Nernst equation for cell.
1 Mark Answer:
Ecell = E°cell - (RT/nF) ln Q.
6. What is anode in galvanic cell?
1 Mark Answer:
Electrode where oxidation occurs.
7. E° for F2/F-?
1 Mark Answer:
2.87 V.
8. Role of salt bridge?
1 Mark Answer:
Maintains electrical neutrality.
9. Faraday constant value?
1 Mark Answer:
96487 C/mol.
10. When Ecell = 0?
1 Mark Answer:
At equilibrium.
Part B: 4 Marks Questions (10 Qs - Medium, Exactly 5 Lines Each)
1. Explain Daniell cell functioning.
4 Marks Answer:
Zn anode oxidizes: Zn → Zn2+ + 2e-.
Cu cathode reduces: Cu2+ + 2e- → Cu.
Electrons flow Zn to Cu; emf 1.1 V at 1 M.
Salt bridge balances ions.
Spontaneous redox converts chemical energy.
2. Differentiate galvanic and electrolytic cells.
4 Marks Answer:
Galvanic: Spontaneous, chemical to electrical.
Electrolytic: Non-spontaneous, electrical to chemical.
Steps: 1. Interface charge, 2. Standard conditions, 3. SHE reference. Ex: Cu 0.34 V. Pitfall: Oxidation vs. reduction. Interlink: Table. Depth: Why unity?
Standard Hydrogen Electrode
Steps: 1. Setup Pt/H2/H+, 2. Zero assignment, 3. Measurement. Ex: Vs. Zn. Pitfall: Pressure ignore. Interlink: Emf. Depth: Arbitrary zero.
Nernst Equation
Steps: 1. Derive from ΔG, 2. Apply Q, 3. 298 K form. Ex: Concentration shift. Pitfall: Log base. Interlink: Equilibrium. Depth: Temp effect.
Key derivations with steps; formulas listed; links to applications. Added Nernst, emf-Gibbs, equilibrium.
Nernst Equation
ΔG = ΔG° + RT ln Q.
ΔG = -nFE, ΔG° = -nFE°.
E = E° - (RT/nF) ln Q.
0.059/n log Q at 298 K.
Depth: Concentration impact.
Cell Emf-Gibbs
ΔG = -nFEcell.
Spontaneous ΔG<0, E>0.
Max work -nFE°.
Equilibrium ΔG=0.
Depth: Thermodynamic link.
Equilibrium Constant
Ecell=0 at eq, Q=K.
0 = E° - (RT/nF) ln K.
log K = nE°/0.059.
K>1 if E°>0.
Depth: Reaction extent.
Electrode Potential
E = E° - (RT/nF) ln(1/[red]/[ox]).
For reduction.
Activity approx concentration.
Dilute solutions.
Depth: Half-cell.
Debates: Standard Conditions
Why 1 M, 298 K?
Activity corrections.
Depth: Real vs. ideal.
Practical Formulas
Ecell = Ecath - Eanod.
n from balanced eq.
Q products/reactants.
Faraday 96500 approx.
Depth: Numerical tips.
Tip: Link to numericals. Depth: Step-by-step proofs. Examples: Daniell apps. Graphs: E vs. log[ion]. Advanced: Temp dependence. Easy: Bullets derivations.
Solved Examples & Numericals - From Text with Simple Explanations
Expanded with evidence, calcs; focus on applications, analysis. Added emf, Nernst, potentials.
Example 1: Daniell Cell Emf
Simple Explanation: Standard calculation.
Step 1: E°Cu = 0.34 V, E°Zn = -0.76 V.
Step 2: Ecell = 0.34 - (-0.76) = 1.10 V.
Step 3: Spontaneous as positive.
Step 4: At 1 M concentrations.
Simple Way: Cathode minus anode standards.
Example 2: Nernst for Daniell
Simple Explanation: Concentration effect.
Step 1: E°cell = 1.10 V, n=2.
Step 2: E = 1.10 - (0.059/2) log([Zn2+]/[Cu2+]).
Step 3: If [Zn2+]=0.1 M, [Cu2+]=1 M: log 0.1 = -1, E=1.10 + 0.0295=1.1295 V.
Step 4: Increases with lower [Zn2+].
Simple Way: Log shifts potential.
Example 3: Cu vs. SHE
Simple Explanation: Measurement.
Step 1: Cell emf 0.34 V with Cu cathode.
Step 2: Ecell = ECu - ESHE = ECu - 0.
Step 3: E°Cu = 0.34 V.
Step 4: Positive, Cu2+ reduces easier than H+.
Simple Way: Emf directly E°.
Example 4: Zn vs. SHE
Simple Explanation: Negative potential.
Step 1: Cell emf -0.76 V with Zn cathode? No, sign indicates.
Step 2: Actual: SHE anode, Zn cathode emf -0.76 V? Convention: E°Zn=-0.76 V.
Step 3: H+ oxidizes Zn.
Step 4: Zn reduces H+.
Simple Way: Negative means reductant.
Example 5: Predict Reaction
Simple Explanation: From table.
Step 1: Cu2+ + Zn → Cu + Zn2+.
Step 2: Ecell = 0.34 - (-0.76) = 1.10 V >0.
Step 3: Spontaneous.
Step 4: Cu2+ oxidizes Zn.
Simple Way: Higher E° oxidant wins.
Example 6: Equilibrium K
Simple Explanation: From E°.
Step 1: log K = nE°/0.059.
Step 2: Daniell n=2, E°=1.10.
Step 3: log K = 2*1.10/0.059 ≈ 37.3.
Step 4: K=10^37.3, highly favored.
Simple Way: Positive E large K.
Tip: Practice self-assess; troubleshoot (e.g., why log?). Added for intext, numericals.
Interactive Quiz - Master Electrochemistry
10 MCQs in full sentences; 80%+ goal. Covers cells, potentials, Nernst.
Quick Revision Notes & Mnemonics
Concise for all subtopics; mnemonics. Covers intro, cells, potentials, Nernst. Expanded all.