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ICSE Class 10 · Chemistry · Chapter 9

Study of Compounds – Ammonia and Nitric Acid

5 topics · 20 questions

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Ammonia (NH₃) - Preparation

  • Laboratory Preparation: Heating ammonium salt with alkali. NH₄Cl + NaOH → NaCl + H₂O + NH₃↑ (or Ca(OH)₂).
  • Setup: Round bottom flask heated gently. NH₃ collected by downward displacement of air (lighter than air) or over mercury.

  • Drying: Passed through CaO or quicklime (not conc. H₂SO₄ as NH₃ reacts with it forming (NH₄)₂SO₄).

    Haber Process: Industrial preparation. N₂ + 3H₂ ⇌ 2NH₃ (at 450-500°C, 200 atm pressure, Fe catalyst).

    Why Downward Collection: NH₃ is lighter than air (M = 17 < 29). Also very soluble in water (1:700), cannot collect over water.

    Laboratory preparation of ammonia gas using ammonium chloride and sodium hydroxide

Properties of Ammonia

  • Physical: Colorless, pungent-smelling gas. Lighter than air. Highly soluble in water (fountain experiment).
  • Basic Nature: Turns red litmus blue. Forms NH₄OH in water: NH₃ + H₂O ⇌ NH₄OH ⇌ NH₄⁺ + OH⁻.
  • Test for NH₃: (1) Turns moist red litmus blue. (2) White fumes with HCl: NH₃ + HCl → NH₄Cl (white dense fumes).
  • With Acids: Forms ammonium salts. NH₃ + HCl → NH₄Cl, 2NH₃ + H₂SO₄ → (NH₄)₂SO₄.
  • Reducing Agent: 2NH₃ + 3CuO → 3Cu + 3H₂O + N₂ (reduces hot copper oxide to copper).
  • Uses: Fertilizers (NH₄NO₃, (NH₄)₂SO₄), refrigerant, cleaning agents, manufacturing HNO₃, explosives.

Nitric Acid (HNO₃) - Preparation

  • Laboratory: KNO₃ + H₂SO₄ → KHSO₄ + HNO₃↑ (heating potassium nitrate with conc. H₂SO₄).
  • Ostwald Process: Industrial method. 4NH₃ + 5O₂ → 4NO + 6H₂O (Pt catalyst, 800°C). 2NO + O₂ → 2NO₂. 4NO₂ + 2H₂O + O₂ → 4HNO₃.
  • Collection: All-glass apparatus (HNO₃ corrodes rubber). Cooled receiver to condense vapors.

  • Why All-glass: HNO₃ is highly corrosive and oxidizing, attacks rubber and cork.

    Concentration: Distilled to get concentrated HNO₃. Pure HNO₃ is colorless, but often yellow due to dissolved NO₂.

    Laboratory preparation of nitric acid using potassium nitrate and concentrated sulfuric acid

Properties of Nitric Acid

  • Physical: Colorless liquid (pure), yellow if contains NO₂. Pungent odor. Fuming if highly concentrated.
  • Acidic Properties: Strong acid, completely ionized. HNO₃ → H⁺ + NO₃⁻. Turns blue litmus red.
  • Oxidizing Agent: Strong oxidizer due to nascent oxygen. 2HNO₃ → 2NO₂ + H₂O + [O].
  • With Metals: With Cu: 3Cu + 8HNO₃ (dil) → 3Cu(NO₃)₂ + 4H₂O + 2NO↑ (brown fumes). Cu + 4HNO₃ (conc) → Cu(NO₃)₂ + 2H₂O + 2NO₂↑.
  • Aqua Regia: HCl:HNO₃ (3:1). Dissolves gold and platinum. Au + HCl + HNO₃ → AuCl₃ + NO + H₂O.
  • With Non-metals: Oxidizes P, S, C to their acids. 3P + 5HNO₃ + 2H₂O → 3H₃PO₄ + 5NO↑.

Ring Test and Uses

  • Brown Ring Test: For NO₃⁻ ions. Add FeSO₄ + conc. H₂SO₄ to solution. Brown ring at junction indicates NO₃⁻.
  • Reaction: NO₃⁻ + 3Fe²⁺ + 4H⁺ → NO + 3Fe³⁺ + 2H₂O. NO + FeSO₄ → [Fe(H₂O)₅NO]SO₄ (brown complex).
  • Uses of HNO₃: Manufacturing fertilizers (NH₄NO₃), explosives (TNT, nitroglycerin), dyes, plastics, medicines.
  • Uses of NH₃: Fertilizers, refrigerant, cleaning (household ammonia), manufacturing HNO₃, nylon, explosives.
  • Concentrated vs Dilute: Conc. HNO₃ gives NO₂ (brown fumes). Dilute HNO₃ gives NO (colorless, turns brown in air).

Quiz

Test your knowledge

Multiple choice

  1. Question 1 of 19Knowledge
    Ammonia is prepared in lab by heating:
  2. Question 2 of 19Knowledge
    Ammonia is collected by:
  3. Question 3 of 19Knowledge
    Ammonia is dried using:
  4. Question 4 of 19Knowledge
    The test for ammonia gas is:
  5. Question 5 of 19Knowledge
    In Haber process, ammonia is formed by:
  6. Question 6 of 19Knowledge
    Nitric acid in lab is prepared from:
  7. Question 7 of 19Knowledge
    Pure nitric acid is:
  8. Question 8 of 19Knowledge
    The brown ring test is used to detect:
  9. Question 9 of 19Assertion-Reasoning
    Assertion (A): Ammonia turns red litmus blue. Reason (R): Ammonia is basic in nature.
  10. Question 10 of 19Knowledge
    Dilute HNO₃ reacts with copper to give:
  11. Question 11 of 19Knowledge
    Concentrated HNO₃ reacts with copper to give:
  12. Question 12 of 19Knowledge
    Aqua regia is a mixture of:
  13. Question 13 of 19Knowledge
    The catalyst used in Ostwald process is:
  14. Question 14 of 19Comprehension
    Ammonia acts as a reducing agent when it reduces:
  15. Question 15 of 19Knowledge
    Which apparatus is used for HNO₃ preparation?
  16. Question 16 of 19Knowledge
    Which gas is evolved when ammonium hydroxide is treated with lead nitrate?
  17. Question 17 of 19Assertion-Reasoning
    Assertion (A): Ammonia is collected by downward displacement of water. Reason (R): Ammonia is lighter than air.
  18. Question 18 of 19Knowledge
    What is the color of the flame when ammonia burns in oxygen?
  19. Question 19 of 19Knowledge
    Which catalyst is used in the laboratory preparation of nitric acid?

Practice numericals

  1. Problem 1 of 1Application

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