Chemistry
Chapter 10
Board Weightage: 8 - 10 Marks in ICSE Board Exam
Study of Compounds: Sulphuric Acid
Prescribed Textbook: Selina Concise Chemistry (Class 10) - Chapter 11
Canonical Link:
https://icse.smartindia.pro/class10_chemistry_study_of_compounds_sulphuric_acid.html
Prerendered HTML Page: class10_chemistry_study_of_compounds_sulphuric_acid.html
📖 Syllabus Scope & Overview
Industrial manufacture by Contact Process: 2SO₂ + O₂ ⇌ 2SO₃ (conditions: 450°C, 1-2 atm, V₂O₅ catalyst), absorption of SO₃ in 98% H₂SO₄ to form Oleum (H₂S₂O₇) (why SO₃ is not dissolved directly in water), diluting oleum to produce H₂SO₄, chemical properties of H₂SO₄: as an acid, non-volatile acid (displaces volatile acids HCl and HNO₃), oxidizing agent (C, S), and dehydrating agent (charring of sugar: C₁₂H₂₂O₁₁ → 12C + 11H₂O).
💡 Core Concepts & Curriculum Outline
Master the fundamental theoretical framework and syllabus scope approved by CISCE.
Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water
Direct absorption of SO₃ in water is highly exothermic, producing a dense, corrosive mist of sulphuric acid droplets that does not condense easily and escapes into the atmosphere. Therefore, SO₃ is absorbed in 98% concentrated H₂SO₄ to form Pyrosulphuric acid (Oleum, H₂S₂O₇), which is then diluted with calculated quantity of water to get acid of desired concentration.
Dehydrating Agent vs Drying Agent
As a dehydrating agent, conc. H₂SO₄ removes chemically combined elements of water (H and O in 2:1 ratio) from compounds, changing their chemical identity. Example: Charring of sugar: C₁₂H₂₂O₁₁ + conc. H₂SO₄ → 12C (black spongy mass of sugar charcoal) + 11H₂O. As a drying agent, it removes only uncombined physical moisture without altering chemical composition.
🔑 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: Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water
1 Mark in Chemical Observation / Balanced Equation
"Highly exothermic dense acid mist"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Highly exothermic dense acid mist" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Highly exothermic dense acid mist" 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 Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water, ensure "Highly exothermic dense acid mist" is explicitly stated in the balanced explanation."
Mandatory Keyword #2
Core Definition
Chapter Concept: Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water
1 Mark in Chemical Observation / Balanced Equation
"Absorbed in 98% H2SO4 to form Oleum (H2S2O7)"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Absorbed in 98% H2SO4 to form Oleum (H2S2O7)" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Absorbed in 98% H2SO4 to form Oleum (H2S2O7)" 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 Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water, ensure "Absorbed in 98% H2SO4 to form Oleum (H2S2O7)" is explicitly stated in the balanced explanation."
Mandatory Keyword #3
Core Definition
Chapter Concept: Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water
1 Mark in Chemical Observation / Balanced Equation
"Vanadium pentoxide (V2O5) catalyst at 450°C"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Vanadium pentoxide (V2O5) catalyst at 450°C" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Vanadium pentoxide (V2O5) catalyst at 450°C" 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 Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water, ensure "Vanadium pentoxide (V2O5) catalyst at 450°C" is explicitly stated in the balanced explanation."
Mandatory Keyword #4
Core Definition
Chapter Concept: Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water
1 Mark in Chemical Observation / Balanced Equation
"Dilution gives 98% pure H2SO4"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Dilution gives 98% pure H2SO4" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Dilution gives 98% pure H2SO4" 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 Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water, ensure "Dilution gives 98% pure H2SO4" is explicitly stated in the balanced explanation."
Mandatory Keyword #5
Core Definition
Chapter Concept: Dehydrating Agent vs Drying Agent
1 Mark in Chemical Observation / Balanced Equation
"Removes chemically combined water (H and O in 2:1)"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Removes chemically combined water (H and O in 2:1)" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Removes chemically combined water (H and O in 2:1)" 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 Dehydrating Agent vs Drying Agent, ensure "Removes chemically combined water (H and O in 2:1)" is explicitly stated in the balanced explanation."
Mandatory Keyword #6
Core Definition
Chapter Concept: Dehydrating Agent vs Drying Agent
1 Mark in Chemical Observation / Balanced Equation
"Charring of sugar into black spongy carbon"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Charring of sugar into black spongy carbon" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Charring of sugar into black spongy carbon" 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 Dehydrating Agent vs Drying Agent, ensure "Charring of sugar into black spongy carbon" is explicitly stated in the balanced explanation."
Mandatory Keyword #7
Experimental Precaution
Chapter Concept: Dehydrating Agent vs Drying Agent
1 Mark in Chemical Observation / Balanced Equation
"Dehydration of oxalic acid and formic acid"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Dehydration of oxalic acid and formic acid" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Dehydration of oxalic acid and formic acid" 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 Dehydrating Agent vs Drying Agent, ensure "Dehydration of oxalic acid and formic acid" is explicitly stated in the balanced explanation."
Mandatory Keyword #8
Core Definition
Chapter Concept: Dehydrating Agent vs Drying Agent
1 Mark in Chemical Observation / Balanced Equation
"Drying agent removes only physical moisture"
📘 Technical Definition & Detailed Description:
In ICSE Class 10 Chemistry (Study of Compounds: Sulphuric Acid), "Drying agent removes only physical moisture" denotes a critical reaction condition, bonding mechanism, stoichiometric rule, or analytical observation required by CISCE.
Examiners award marks specifically when "Drying agent removes only physical moisture" 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 Dehydrating Agent vs Drying Agent, ensure "Drying agent removes only physical moisture" 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 10 - Section Review Q.3
Selina Concise Chemistry (Class 10) - Chapter 11 - Review Exercise 10
3 Marks Total
In the study of Study of Compounds: Sulphuric Acid: (i) Give a balanced chemical equation or reaction mechanism illustrating Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water. (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 10
2 Marks Total
Define "Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water" 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: Direct absorption of SO₃ in water is highly exothermic, producing a dense, corrosive mist of sulphuric acid droplets that does not condense easily and escapes into the atmosphere. ...
1 Mark
Step 2: Mandatory Technical Criteria: Ensure the definition contains mandatory keywords: Highly exothermic dense acid mist, Absorbed in 98% H2SO4 to form Oleum (H2S2O7), Vanadium pentoxide (V2O5) catalyst at 450°C.
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 "Dehydrating Agent vs Drying Agent". 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 Dehydrating Agent vs Drying Agent.
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 Dehydrating Agent vs Drying Agent
(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 "Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water" and "Dehydrating Agent vs Drying Agent" 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: Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water focuses on Highly exothermic dense acid mist, whereas Dehydrating Agent vs Drying Agent emphasizes Removes chemically combined water (H and O in 2:1).
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 "Study of Compounds: Sulphuric Acid":
(i) State the fundamental law or rule governing "Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water". [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 Highly exothermic dense acid mist with related quantities. The correct understanding requires strict application of Dehydrating Agent vs Drying Agent.
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 "Study of Compounds: Sulphuric Acid": An experiment is performed under non-ideal conditions involving "Contact Process: Why SO₃ is Dissolved in H₂SO₄, not Water" and "Dehydrating Agent vs Drying Agent".
(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: Highly exothermic dense acid mist, Absorbed in 98% H2SO4 to form Oleum (H2S2O7), Vanadium pentoxide (V2O5) catalyst at 450°C, Dilution gives 98% pure H2SO4.
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.