Run the full laboratory preparation of ammonia, walk through every identification test, and lock in the theory with a self-marking quiz — all in one interactive simulation.
From Priestley’s first isolation to the Haber–Bosch process that feeds the planet.
First isolated: 1774 by Joseph Priestley
Named: From the ancient Egyptian temple “Amun” — “Sal Ammoniacum” (salt of Ammon)
Ancient knowledge: Known to alchemists in the 13th century
Ammonia revolutionized agriculture by enabling mass production of nitrogen fertilizers. The Haber Process is considered one of the most important chemical innovations, feeding billions of people globally.
N₂ → NH₃ → NO₂⁻ → NO₃⁻ → Plants → Animals → Decay → NH₃
This cycle is essential for all life on Earth and maintains soil fertility.
| Property | Value / Description |
|---|---|
| Molecular Formula | NH₃ |
| Molar Mass | 17.03 g/mol |
| Appearance | Colorless gas |
| Odor | Pungent, characteristic (fish-like) |
| Density | 0.73 kg/m³ (d = 0.59 relative to air) |
| Boiling Point | −33.34 °C |
| Melting Point | −77.73 °C |
| Solubility in Water | Very high: 470 g/L at 20 °C (forms NH₄OH) |
| pH (solution) | Weakly basic (pH ≈ 11, dilute) |
| Flammability | Non-flammable; burns in O₂ above 651 °C |
| Toxicity | Toxic — respiratory irritant (TLV: 25 ppm) |
NH₃ + H₂O ⇌ NH₄⁺ + OH⁻
Acts as a weak base due to the lone pair on nitrogen.
NH₃ + HCl → NH₄Cl
Forms dense white fumes — the classic test for ammonia.
4NH₃ + 3O₂ → 2N₂ + 6H₂O
Burns in oxygen with a pale yellow flame.
2NH₃ + 3CuO → N₂ + 3Cu + 3H₂O
Acts as a reducing agent — Cu²⁺ is reduced to Cu.
Principle: Direct combination of nitrogen and hydrogen under controlled conditions.
N₂ + 3H₂ ⇌ 2NH₃ (+92.4 kJ/mol)
Low temperature: favors NH₃ (exothermic) but slows the rate
High pressure: favors NH₃ (fewer gas moles on product side)
Compromise: ~450 °C and 200–300 atm balances rate and yield
The Haber Process produces ~170 million tons of ammonia annually, supporting nitrogen fertilizer supply for roughly 40% of the world’s food production.
From ammonium chloride and calcium hydroxide, by gentle heating.
2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2NH₃↑ + 2H₂O
An acid–base reaction: ammonium chloride (acidic salt) reacts with calcium hydroxide (base).
| Stage | Observation | Reason |
|---|---|---|
| Before Heating | Mixture is pale yellow/white, solid | NH₄Cl and Ca(OH)₂ are solids |
| During Gentle Heating | Pungent smell detected | NH₃ gas begins to evolve |
| Gas Evolution | White fumes appear (mist in tube) | NH₃ dissolves in water vapor, forming visible droplets |
| At Drying Tower | Gas passes through quicklime | Water vapor absorbed by CaO; dry NH₃ emerges |
| Gas Collection | Jar fills from top downward | NH₃ is lighter than air (M = 17 vs air M ≈ 29) |
| After Heating Stops | Residue is CaCl₂ solution (liquid) | Reaction went to completion |
Six ways to identify NH₃, ranked by sensitivity and specificity.
Carefully waft the gas toward the nose and smell cautiously — never inhale deeply.
✓ Positive: pungent, fishy/urine-like odor
Ammonia is highly volatile and odorous — the pungent smell is a direct property of NH₃ molecules.
Hold a moist red litmus paper at the mouth of the tube.
✓ Positive: red litmus turns blue
NH₃ + H₂O ⇌ NH₄⁺ + OH⁻
The OH⁻ formed makes the solution basic, turning red litmus blue.
Bring a glass rod dipped in concentrated HCl near the mouth of the tube.
✓ Positive: dense white smoke at the junction
NH₃ + HCl → NH₄Cl↓ (white solid)
Dissolve NH₃ in water and add CuSO₄ solution dropwise.
✓ Initial: blue precipitate Cu(OH)₂
✓ Excess NH₃: precipitate dissolves to deep blue solution
Cu(OH)₂ + 4NH₃ → [Cu(NH₃)₄]²⁺
Add Nessler’s reagent (K₂HgI₄ in KOH) to an aqueous ammonia sample.
✓ Concentrated: reddish-brown color
✓ Dilute: yellow color
The most sensitive and specific test — used in analytical / quantitative methods.
Add phenolphthalein indicator to an aqueous ammonia sample.
✓ Positive: colorless → pink/magenta
Colorless below pH 8.2, pink above pH 8.2 — matching ammonia’s basic pH.
| Test | Reagent | Observation | Sensitivity | Specificity |
|---|---|---|---|---|
| Smell | None | Pungent odor | High | Not specific |
| Red Litmus | Litmus paper | Turns blue | Moderate | Not specific |
| HCl Fumes | HCl gas | White fumes | Very High | Highly specific |
| CuSO₄ | Copper sulfate | Blue complex | High | Specific |
| Nessler’s Reagent | K₂HgI₄/KOH | Brown / yellow | Highest | Highly specific |
| Phenolphthalein | Phenolphthalein | Pink color | Moderate | Not specific |
Six questions covering theory, the experiment, and the tests.