Why these three chemicals matter
Ammonia, nitric acid and sulphuric acid show up in almost every chemistry exam. They are also the backbone of many everyday products – from fertilizers to cleaning agents.
💡 In Simple Words: Ammonia is a smelly gas used to make fertilizers. Nitric acid is a strong acid that helps grow plants and make explosives. Sulphuric acid is a super‑strong acid used in batteries and to clean metal.
What is Ammonia?
Ammonia (NH3) is a colourless gas with a pungent smell. Think of it as a tiny bunch of nitrogen and hydrogen atoms holding hands.
How is ammonia prepared in the lab?
The classic lab method mixes a solid metal like zinc with a dilute acid such as hydrochloric acid. The metal gives up electrons, the acid gives up hydrogen ions, and you get ammonia gas.
Equation: Zn + 2HCl → ZnCl2 + H2↑ then N2 + 3H2 → 2NH3
Industrial preparation – the Haber process
On a huge scale, ammonia is made by combining nitrogen from the air with hydrogen (usually from natural gas) under high pressure and temperature, with an iron catalyst.
Key properties and uses
- Formula: NH3
- Physical state: Gas at room temperature
- Acidity: Weak base – it can accept a proton (H⁺) from water, forming NH4⁺.
- Uses: Fertiliser (ammonium nitrate), refrigerant, cleaning agent.
What is Nitric Acid?
Nitric acid (HNO3) is a colourless, highly corrosive liquid. It smells sharp, like a lab. It is one of the three “strong acids” you learn early on.
Lab preparation
Mixing concentrated sulfuric acid with sodium nitrate (or potassium nitrate) drives off nitrogen dioxide gas, which then reacts with water to give nitric acid.
Equation (simplified): NaNO3 + H2SO4 → NaHSO4 + HNO3
Important properties
- Formula: HNO3
- Strength: Strong acid – dissociates completely in water.
- Oxidising power: Can take electrons from other substances, which is why it helps make explosives like TNT.
- Uses: Fertiliser (ammonium nitrate), making dyes, etching metals.
What is Sulphuric Acid?
Sulphuric acid (H2SO4) is a thick, oily liquid. It’s the heavyweight champion of acids – very strong and very drying.
Lab preparation (old method)
Heat sulphur (S) with concentrated nitric acid. The reaction produces sulphur dioxide gas, which is then absorbed in water to give sulphuric acid.
Equation (simplified): S + 2HNO3 → SO2 + 2NO2 + H2O → H2SO4
Key properties
- Formula: H2SO4
- Strength: Strong acid – fully ionises in water.
- Dehydrating nature: Pulls water out of other substances, like a sponge that only likes to hold onto water.
- Uses: Batteries, car washes, making detergents, industrial cleaning.
Quick comparison
| Property | Ammonia (NH3) | Nitric Acid (HNO3) | Sulphuric Acid (H2SO4) |
|---|---|---|---|
| State at RT | Gas | Liquid | Liquid |
| Acid/Base nature | Weak base | Strong acid | Strong acid |
| Key industrial use | Fertiliser | Explosives & fertilizers | Battery acid & detergents |
| Preparation method | Haber process (N₂+3H₂) | H₂SO₄ + NaNO₃ → HNO₃ | Contact process (SO₃+H₂O) |
Things to remember for the ICSE exam
- Write balanced equations for lab preparations – the exam loves balanced equations.
- Know the physical state and acid/base character of each compound.
- Remember one major use for each; it often appears in short‑answer questions.
- For sulphuric acid, recall that it is a dehydrating agent – a classic test question.
- In the Haber process, the catalyst is iron and the conditions are high pressure (≈150 atm) and temperature (≈450 °C).
📝 Likely Exam Questions
- Write the balanced chemical equation for the laboratory preparation of ammonia using zinc and hydrochloric acid.
Answer: Zn + 2HCl → ZnCl₂ + H₂↑ followed by N₂ + 3H₂ → 2NH₃ (if nitrogen source is provided). - Why is sulphuric acid called a dehydrating agent? Give an example.
Answer: It removes water from substances because it has a strong affinity for water molecules. Example: Sugar turns black when heated with concentrated H₂SO₄ as water is stripped away. - List two important uses of nitric acid in industry.
Answer: Production of fertilizers (e.g., ammonium nitrate) and manufacturing of explosives such as TNT. - Describe the Haber process in brief.
Answer: Nitrogen from air and hydrogen (from natural gas) are combined at about 150 atm and 450 °C in the presence of an iron catalyst to form ammonia (N₂ + 3H₂ → 2NH₃). - Differentiate between a strong acid and a weak base with examples from this note.
Answer: A strong acid (e.g., HNO₃) dissociates completely in water, releasing many H⁺ ions. A weak base (e.g., NH₃) only partially accepts H⁺ ions, forming a small amount of NH₄⁺ in solution.