Chemistry
Chapter 6
Board Weightage: 10 - 12 Marks in ICSE Board Exam
Electrolysis: Principles & Industrial Applications
Prescribed Textbook: Selina Concise Chemistry (Class 10) - Chapter 6
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📖 Syllabus Scope & Overview
Electrolytes vs non-electrolytes, strong and weak electrolytes, electrochemical series and preferential / selective discharge of ions at electrodes, electrolysis of molten lead bromide (PbBr₂), acidified water (Hoffmann voltameter), and aqueous copper sulphate (CuSO₄) with platinum and copper electrodes; industrial applications: electroplating (nickel and silver) and electro-refining of copper.
💡 Core Concepts & Curriculum Outline
Master the fundamental theoretical framework and syllabus scope approved by CISCE.
Electrolysis of Molten Lead Bromide (PbBr₂)
Crucible made of silica (withstands high heat, non-conducting). Anode: Graphite (inert, resists corrosive bromine vapors). Cathode: Graphite. At cathode: Pb²⁺ + 2e⁻ → Pb (silvery grey lead metal deposits). At anode: 2Br⁻ - 2e⁻ → Br₂ (reddish-brown bromine vapors evolve). Silica crucible is heated externally because solid PbBr₂ is non-conducting; heat keeps it molten.
Electroplating of an Article with Nickel / Silver
Article to be electroplated is ALWAYS made the CATHODE (clean, greaseless). Pure block of plating metal (Ni/Ag) is made the ANODE. Electrolyte must contain ions of the plating metal. Current used must be DIRECT CURRENT (DC) of low magnitude for a longer duration to produce a smooth, firm, and uniform deposit (AC causes alternating deposition and dissolution).
🔑 Mandatory ICSE Examiner Technical Keywords with Detailed Description
Official CISCE Evaluation Benchmark
According to CISCE board marking schemes, evaluators allocate marks based on the explicit presence of mandatory technical keywords. General or colloquial explanations fail to secure full marks. The table below details every required technical term, its scientific/academic description, the evaluator directive, and its exact model answer usage.
Mandatory Keyword #1
Core Definition
Chapter Concept: Electrolysis of Molten Lead Bromide (PbBr₂)
1 Mark in Chemical Observation / Balanced Equation
"Silica crucible"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Silica crucible" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Silica crucible" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electrolysis of Molten Lead Bromide (PbBr₂), ensure "Silica crucible" is explicitly stated in the balanced explanation."
Mandatory Keyword #2
Core Definition
Chapter Concept: Electrolysis of Molten Lead Bromide (PbBr₂)
1 Mark in Chemical Observation / Balanced Equation
"Graphite anode resists bromine attack"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Graphite anode resists bromine attack" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Graphite anode resists bromine attack" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electrolysis of Molten Lead Bromide (PbBr₂), ensure "Graphite anode resists bromine attack" is explicitly stated in the balanced explanation."
Mandatory Keyword #3
Core Definition
Chapter Concept: Electrolysis of Molten Lead Bromide (PbBr₂)
1 Mark in Chemical Observation / Balanced Equation
"Cathode: Silvery grey metal (Pb)"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Cathode: Silvery grey metal (Pb)" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Cathode: Silvery grey metal (Pb)" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electrolysis of Molten Lead Bromide (PbBr₂), ensure "Cathode: Silvery grey metal (Pb)" is explicitly stated in the balanced explanation."
Mandatory Keyword #4
Core Definition
Chapter Concept: Electrolysis of Molten Lead Bromide (PbBr₂)
1 Mark in Chemical Observation / Balanced Equation
"Anode: Reddish brown vapours (Br2)"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Anode: Reddish brown vapours (Br2)" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Anode: Reddish brown vapours (Br2)" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electrolysis of Molten Lead Bromide (PbBr₂), ensure "Anode: Reddish brown vapours (Br2)" is explicitly stated in the balanced explanation."
Mandatory Keyword #5
Core Definition
Chapter Concept: Electroplating of an Article with Nickel / Silver
1 Mark in Chemical Observation / Balanced Equation
"Article is always the CATHODE"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Article is always the CATHODE" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Article is always the CATHODE" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electroplating of an Article with Nickel / Silver, ensure "Article is always the CATHODE" is explicitly stated in the balanced explanation."
Mandatory Keyword #6
Core Definition
Chapter Concept: Electroplating of an Article with Nickel / Silver
1 Mark in Chemical Observation / Balanced Equation
"Pure metal is ANODE"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Pure metal is ANODE" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Pure metal is ANODE" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electroplating of an Article with Nickel / Silver, ensure "Pure metal is ANODE" is explicitly stated in the balanced explanation."
Mandatory Keyword #7
Mathematical Rule
Chapter Concept: Electroplating of an Article with Nickel / Silver
1 Mark in Chemical Observation / Balanced Equation
"Direct current (DC) of low value"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Direct current (DC) of low value" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Direct current (DC) of low value" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electroplating of an Article with Nickel / Silver, ensure "Direct current (DC) of low value" is explicitly stated in the balanced explanation."
Mandatory Keyword #8
Core Definition
Chapter Concept: Electroplating of an Article with Nickel / Silver
1 Mark in Chemical Observation / Balanced Equation
"Uniform, smooth deposit"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Electrolysis: Principles & Industrial Applications), "Uniform, smooth deposit" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Uniform, smooth deposit" is included alongside balanced chemical equations, observable color changes, or state symbols (s, l, g, aq).
📝 Model Answer Application (Exact Phrasing for Board Exam):
"During the reaction in Electroplating of an Article with Nickel / Silver, ensure "Uniform, smooth deposit" is explicitly stated in the balanced explanation."
Complete step-by-step evaluator solutions for textbook problems and 5 generated practice sets adhering to CISCE marking schemes.
📘 Textbook Problem: Textbook Exercise 6 - Section Review Q.3
Selina Concise Chemistry (Class 10) - Chapter 6 - Review Exercise 6
3 Marks Total
In the study of Electrolysis: Principles & Industrial Applications: (i) Give a balanced chemical equation or reaction mechanism illustrating Electrolysis of Molten Lead Bromide (PbBr₂). (ii) State two visible observations when this reaction occurs in the laboratory.
Step-by-Step Marking Breakdown
Step 1: Write Balanced Chemical Equation: Write the complete chemical equation with correct molecular formulas, balancing coefficients, and state symbols (s, l, g, aq).
1 Mark
Step 2: Detail First Characteristic Observation: State the primary sensory observation (e.g. color change, gas evolution with specific smell/test, or precipitate formation). Do not simply state the chemical name of the product formed.
1 Mark
Step 3: Detail Second Observation and Chemical Inference: State the second distinguishing property or test verifying the chemical reaction has reached completion.
1 Mark
Final Answer: Balanced equation and distinct physical observations confirmed
(Units: State symbols (s, l, g, aq))
💡 Examiner Tip: In ICSE Chemistry, an "observation" must describe what is physically seen, smelled, or heard, NOT just naming the compound formed.
🎯 Generated Set: Generated Practice Set 1 - Core Concept (2 Marks)
ICSE Class 10 Exam Blueprint - Chapter 6
2 Marks Total
Define "Electrolysis of Molten Lead Bromide (PbBr₂)" in the context of ICSE Class 10 Chemistry. State its primary characteristic or SI unit/standard symbol.
Step-by-Step Marking Breakdown
Step 1: Precise Technical Definition: Crucible made of silica (withstands high heat, non-conducting). Anode: Graphite (inert, resists corrosive bromine vapors). Cathode: Graphite. At cathode: Pb²⁺ + 2e⁻ → Pb (silvery g...
1 Mark
Step 2: Mandatory Technical Criteria: Ensure the definition contains mandatory keywords: Silica crucible, Graphite anode resists bromine attack, Cathode: Silvery grey metal (Pb).
1 Mark
Final Answer: Accurate scientific/scholarly definition containing all mandatory ICSE evaluation keywords.
(Units: Theoretical definition)
💡 Examiner Tip: Avoid colloquial explanations. Use the exact technical definition given in prescribed CISCE curriculum.
🎯 Generated Set: Generated Practice Set 2 - Method & Application (3 Marks)
ICSE Question Bank & Specimen Framework - Chemistry
3 Marks Total
Explain the procedural method or practical demonstration used to verify "Electroplating of an Article with Nickel / Silver". State the working apparatus/setup and key precautions.
Step-by-Step Marking Breakdown
Step 1: State the Formula / Conceptual Principle: State the fundamental principle governing Electroplating of an Article with Nickel / Silver.
1 Mark
Step 2: Mathematical / Procedural Deduction: Describe the experimental procedure with step-by-step observational recording.
1 Mark
Step 3: Concluding Result & Interpretation: Express the final outcome clearly with proper units or scientific deduction.
1 Mark
Final Answer: Verified procedural conclusion for Electroplating of an Article with Nickel / Silver
(Units: Procedural steps)
💡 Examiner Tip: In derivation and numerical questions, every intermediate mathematical step carries fractional credit.
🎯 Generated Set: Generated Practice Set 3 - Comparative Analysis (3 Marks)
ICSE Exemplar Practice Paper - Chemistry
3 Marks Total
Differentiate between "Electrolysis of Molten Lead Bromide (PbBr₂)" and "Electroplating of an Article with Nickel / Silver" on the basis of: (i) Fundamental definition/mechanism, (ii) Key working condition or formula, (iii) Real-world practical example or application.
Step-by-Step Marking Breakdown
Point 1: Conceptual Difference: Contrast the primary mechanisms: Electrolysis of Molten Lead Bromide (PbBr₂) focuses on Silica crucible, whereas Electroplating of an Article with Nickel / Silver emphasizes Article is always the CATHODE.
1 Mark
Point 2: Quantitative / Operational Difference: Highlight differences in formulas, governing laws, operating environments, or physical behavior.
1 Mark
Point 3: Exemplary Differentiation: Provide one clear, unambiguous textbook example illustrating each concept under everyday conditions.
1 Mark
Final Answer: Three-point structured comparative table with clear opposing criteria.
(Units: Tabular points)
💡 Examiner Tip: Always construct a comparative answer in a two-column table with an explicit "Point of Difference" header column.
🎯 Generated Set: Generated Practice Set 4 - Board Standard Structured (4 Marks)
ICSE Board Marking Blueprint - Class 10
4 Marks Total
A comprehensive ICSE examination question based on "Electrolysis: Principles & Industrial Applications":
(i) State the fundamental law or rule governing "Electrolysis of Molten Lead Bromide (PbBr₂)". [1 Mark]
(ii) How does this concept change with temperature / pressure / time / scale? [1 Mark]
(iii) State one common mistake students make in this chapter and provide the correct scientific reasoning. [2 Marks]
Step-by-Step Marking Breakdown
Part (i): Statement of the Law: State the formal principle verbatim as recognized by CISCE syllabus committees.
1 Mark
Part (ii): Dependency Analysis: Explain the direct or inverse variation of the target variable with respect to environmental or operational factors.
1 Mark
Part (iii): Error Analysis & Correct Resolution: Identify the frequent pitfall: Students often confuse Silica crucible with related quantities. The correct understanding requires strict application of Electroplating of an Article with Nickel / Silver.
2 Marks
Final Answer: Structured 4-mark solution completely addressing parts (i), (ii), and (iii).
(Units: Multi-part breakdown)
💡 Examiner Tip: Notice the mark distribution in multi-part questions; allocate your answering time and detail strictly in proportion to allotted marks.
🎯 Generated Set: Generated Practice Set 5 - Higher Order Thinking (HOTS) (4 Marks)
ICSE High-Achiever Challenge Series - Class 10
4 Marks Total
A critical scenario-based problem in "Electrolysis: Principles & Industrial Applications": An experiment is performed under non-ideal conditions involving "Electrolysis of Molten Lead Bromide (PbBr₂)" and "Electroplating of an Article with Nickel / Silver".
(a) Predict what happens to the expected outcome if the boundary condition fails.
(b) Give complete scientific justification.
(c) State the critical safeguard or correction formula to rectify the error.
Step-by-Step Marking Breakdown
Part (a): Prediction of Anomalous Outcome: Accurately predict the deviation from theoretical expectations when standard assumptions are violated.
1 Mark
Part (b): Scientific Justification: Provide a rigorous scientific explanation using first principles and mandatory keywords: Silica crucible, Graphite anode resists bromine attack, Cathode: Silvery grey metal (Pb), Anode: Reddish brown vapours (Br2).
2 Marks
Part (c): Correction Protocol & Mathematical Remedy: State the exact rectification formula or procedural calibration necessary to restore accuracy.
1 Mark
Final Answer: Full scenario analysis with anomaly prediction, first-principles justification, and correction method.
(Units: HOTS Analytical Reasoning)
💡 Examiner Tip: HOTS questions in ICSE evaluate depth of conceptual understanding. Avoid superficial guessing; reason backward from core laws.