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Study of Compounds – Sulphuric Acid

ICSE Grade 10 Chemistry - Chapter 10

📚 Smart Summary

1. Contact Process - Industrial Preparation

Contact Process: Industrial method to manufacture H₂SO₄. Three main steps.

Step 1 - SO₂ Formation: Burning sulphur or roasting metal sulphides. S + O₂ → SO₂ or 4FeS₂ + 11O₂ → 2Fe₂O₃ + 8SO₂.

Step 2 - SO₃ Formation: 2SO₂ + O₂ ⇌ 2SO₃ (V₂O₅ catalyst, 450°C, 1-2 atm). Reversible, exothermic reaction.

Step 3 - Oleum Formation: SO₃ dissolved in conc. H₂SO₄ to form oleum (H₂S₂O₇). SO₃ + H₂SO₄ → H₂S₂O₇.

Final Step: Oleum diluted with water. H₂S₂O₇ + H₂O → 2H₂SO₄.

Contact process for sulfuric acid production

Industrial preparation of sulfuric acid using the Contact process with vanadium pentoxide catalyst

Why Not Direct: SO₃ + H₂O → H₂SO₄ forms mist which is difficult to condense. Oleum method prevents this.

2. Properties of Sulphuric Acid

Physical Properties: Colorless, dense, oily liquid. Boiling point: 338°C. Miscible with water (highly exothermic).

Dilution: Always add acid to water, NEVER water to acid. Highly exothermic - water may boil and splash.

Hygroscopic: Absorbs moisture from air without dissolving. Used as drying agent.

Dehydrating Agent: Removes water from compounds. C₁₂H₂₂O₁₁ + H₂SO₄ → 12C (black) + 11H₂O (charring of sugar).

Acidic Properties: Strong dibasic acid. H₂SO₄ → 2H⁺ + SO₄²⁻. Neutralizes bases, reacts with metals, carbonates.

With Metals: Dilute acid: Zn + H₂SO₄ → ZnSO₄ + H₂↑. Conc. acid: Cu + 2H₂SO₄ (conc) → CuSO₄ + SO₂↑ + 2H₂O.

3. Special Properties and Reactions

Oxidizing Agent: Hot concentrated H₂SO₄ acts as oxidizing agent. H₂SO₄ → H₂O + SO₂ + [O].

With Non-metals: C + 2H₂SO₄ (conc) → CO₂ + 2SO₂ + 2H₂O. S + 2H₂SO₄ (conc) → 3SO₂ + 2H₂O.

With HX Acids: Displaces volatile acids. NaCl + H₂SO₄ → NaHSO₄ + HCl↑ (used to prepare HCl, HNO₃).

With Salts: Forms sulphates. CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂↑.

Test for SO₄²⁻ ions: BaCl₂ + H₂SO₄ → BaSO₄↓ (white precipitate, insoluble in dil. HNO₃). Confirmatory test for sulphates.

Concentrated vs Dilute: Dilute - typical acid properties (H₂ with metals). Concentrated - oxidizing, dehydrating properties.

4. Uses of Sulphuric Acid

Fertilizers: Manufacturing ammonium sulphate (NH₄)₂SO₄, superphosphate Ca(H₂PO₄)₂.

Petroleum Refining: Removing impurities from petroleum products.

Lead-Acid Battery: Electrolyte in car batteries (dilute H₂SO₄).

Manufacturing: Paints, pigments, dyes, detergents, plastics, explosives.

Chemical Industry: Making other acids (HCl, HNO₃), salts, cleaning agents.

Laboratory Reagent: Drying gases, catalyst, pH adjustment.

Called 'King of Chemicals': Most important industrial chemical due to wide applications.

5. Important Reactions Summary

Dilute H₂SO₄ + Metal: Zn + H₂SO₄ (dil) → ZnSO₄ + H₂↑ (hydrogen evolution).

Conc. H₂SO₄ + Cu: Cu + 2H₂SO₄ (conc) → CuSO₄ + SO₂↑ + 2H₂O (SO₂ gas, acts as oxidizing agent).

With Carbonate: Na₂CO₃ + H₂SO₄ → Na₂SO₄ + H₂O + CO₂↑ (effervescence).

With Base: 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O (neutralization).

Dehydration: CuSO₄·5H₂O + conc. H₂SO₄ → CuSO₄ (anhydrous) + 5H₂O (removes water of crystallization).

Safety: Handle with care - corrosive, causes severe burns. Neutralize spills with sodium bicarbonate.

🎯 Test Your Knowledge

Multiple Choice Questions

1. The catalyst used in Contact process is:

2. While diluting concentrated sulphuric acid:

3. Concentrated H₂SO₄ is used as a drying agent because it is:

4. When conc. H₂SO₄ is added to sugar, it turns black because:

5. The basicity of H₂SO₄ is:

6. The test for sulphate ions involves:

7. When dilute H₂SO₄ reacts with zinc, the gas evolved is:

8. When concentrated H₂SO₄ reacts with copper, the gas evolved is:

9. Assertion (A): H₂SO₄ is called 'King of Chemicals'. Reason (R): It has many industrial applications.

10. In Contact process, SO₃ is dissolved in conc. H₂SO₄ to form:

11. H₂SO₄ is used in lead-acid battery as:

12. The molecular mass of H₂SO₄ is:

13. Concentrated H₂SO₄ cannot be used to dry:

14. In Contact process, the optimum temperature for SO₃ formation is:

15. Which gas is produced when NaCl reacts with conc. H₂SO₄?