Step-by-step ICSE solutions and marking scheme for Study of Compounds: Sulphuric Acid from Selina Concise Chemistry (Class 10) - Chapter 11 and 5 generated practice problem sets.

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Chemistry Chapter 10 1 Textbook + 5 Generated Exercises 8 - 10 Marks in ICSE Board Exam

Study of Compounds: Sulphuric Acid — Solved Textbook & 5 Practice Sets

Prescribed Reference Textbook: Selina Concise Chemistry (Class 10) - Chapter 11

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📘 Prescribed Textbook Solved Exercise (Selina Concise Chemistry (Class 10))

Primary Curriculum Benchmark

Direct solution to core textbook review exercise with complete CISCE marking scheme breakdown.

Textbook Exercise 10 - Section Review Q.3 Selina Concise Chemistry (Class 10) - Chapter 11 - Review Exercise 10

3 Marks Allotted

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 ICSE Evaluator Marking Key

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 Verified Answer: Balanced equation and distinct physical observations confirmed (Key Units: State symbols (s, l, g, aq))

💡 Examiner Directive: In ICSE Chemistry, an "observation" must describe what is physically seen, smelled, or heard, NOT just naming the compound formed.

🎯 5 Generated Practice Exercises with Step-Marking

CISCE Syllabus Graded Set

Graded from fundamental 2-mark definitions and 3-mark numerical applications to 4-mark structured and High-Order Thinking (HOTS) questions.

Generated Practice Set 1 - Core Concept (2 Marks) Difficulty: Easy

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 Directive: Avoid colloquial explanations. Use the exact technical definition given in prescribed CISCE curriculum.

Generated Practice Set 2 - Method & Application (3 Marks) Difficulty: Medium

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 Directive: In derivation and numerical questions, every intermediate mathematical step carries fractional credit.

Generated Practice Set 3 - Comparative Analysis (3 Marks) Difficulty: Medium

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 Directive: Always construct a comparative answer in a two-column table with an explicit "Point of Difference" header column.

Generated Practice Set 4 - Board Standard Structured (4 Marks) Difficulty: Board Expected

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 Directive: Notice the mark distribution in multi-part questions; allocate your answering time and detail strictly in proportion to allotted marks.

Generated Practice Set 5 - Higher Order Thinking (HOTS) (4 Marks) Difficulty: Hard

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 Directive: HOTS questions in ICSE evaluate depth of conceptual understanding. Avoid superficial guessing; reason backward from core laws.

🔑 Mandatory ICSE Examiner Technical Keywords Required in Solutions

Required for Step-Marking Credit

CISCE evaluators check for the explicit usage of mandatory technical terminology when scoring reasoning questions and step derivations. The table below outlines each key term, its technical description, the examiner marking directive, and the exact model answer phrasing expected in ICSE board examination solutions.

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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"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.

⚠️ CISCE Examiner Directive & Marking Rubric:

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 Solutions):

"During the reaction in Dehydrating Agent vs Drying Agent, ensure "Drying agent removes only physical moisture" is explicitly stated in the balanced explanation."

⚖️ CISCE Evaluation Directives for Chemistry

Step-Mark Allocation: Every sub-step, formula statement, and intermediate substitution carries independent marks. Writing final answers without formula yields zero in Section B numericals.

Mandatory SI Units: In ICSE Science and Mathematics, omitting SI units or writing incorrect unit exponents causes automatic 1/2 mark deduction per problem.

Examiner Technical Vocabulary: CISCE evaluators look for exact prescribed terms in definitions and reasoning questions. General paraphrasing often loses full credit.

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