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Study of Compounds – Ammonia and Nitric Acid

ICSE Grade 10 Chemistry - Chapter 9

📚 Smart Summary

1. 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 setup for ammonia gas preparation

Laboratory preparation of ammonia gas using ammonium chloride and sodium hydroxide

2. 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.

3. 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 setup for nitric acid preparation

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

4. 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↑.

5. 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).

🎯 Test Your Knowledge

Multiple Choice Questions

1. Ammonia is prepared in lab by heating:

2. Ammonia is collected by:

3. Ammonia is dried using:

4. The test for ammonia gas is:

5. In Haber process, ammonia is formed by:

6. Nitric acid in lab is prepared from:

7. Pure nitric acid is:

8. The brown ring test is used to detect:

9. Assertion (A): Ammonia turns red litmus blue. Reason (R): Ammonia is basic in nature.

10. Dilute HNO₃ reacts with copper to give:

11. Concentrated HNO₃ reacts with copper to give:

12. Aqua regia is a mixture of:

13. The catalyst used in Ostwald process is:

14. Ammonia acts as a reducing agent when it reduces:

15. Which apparatus is used for HNO₃ preparation?

16. Which gas is evolved when ammonium hydroxide is treated with lead nitrate?

17. Assertion (A): Ammonia is collected by downward displacement of water. Reason (R): Ammonia is lighter than air.

18. What is the color of the flame when ammonia burns in oxygen?

19. Which catalyst is used in the laboratory preparation of nitric acid?

Practice Numericals

Practice Problem 1: Calculate the mass of nitric acid produced from 8.5 g of ammonia in Ostwald process. (Atomic masses: N=14, H=1, O=16)