Why should you care about ammonia, nitric acid and sulphuric acid?
These three chemicals are the backbone of many everyday products – from fertilizers that grow our food to cleaners that keep our homes sparkling.
💡 In Simple Words: Ammonia, nitric acid and sulphuric acid are like the three main ingredients in a recipe that makes fertilizers, explosives and cleaning agents. Knowing how they’re made and what they do helps you ace chemistry exams.
What is Ammonia?
Ammonia (NH3) is a colour‑less gas with a sharp, pungent smell. Think of it as a tiny bundle of nitrogen and hydrogen atoms that love to share electrons.
How is Ammonia Made?
The most important industrial method is the Haber‑Bosch process. It mixes nitrogen from the air (N2) with hydrogen (H2) at high pressure (150‑200 atm) and temperature (400‑500 °C) over an iron catalyst.
Equation: N2 + 3H2 → 2NH3
Imagine squeezing water through a narrow pipe – the pressure forces the molecules together, just like the high pressure pushes nitrogen and hydrogen to bond.
Properties of Ammonia
- Colourless, pungent gas.
- Very soluble in water – forms a basic solution called ammonium hydroxide.
- Boils at –33 °C (so it turns to liquid in a fridge).
What is Nitric Acid?
Nitric acid (HNO3) is a strong, corrosive liquid that smells like sharp vinegar. It’s the main source of nitrogen for fertilizers and also used in making explosives.
Industrial Preparation of Nitric Acid (Ostwald Process)
The process starts with ammonia, then adds oxygen and water in a series of steps. Here’s a quick flowchart to visualise it:
Step 1: Ammonia reacts with oxygen over a platinum‑rhodium catalyst to give nitric oxide (NO).
Step 2: NO grabs another oxygen molecule to become nitrogen dioxide (NO2).
Step 3: NO2 dissolves in water and forms nitric acid.
Properties of Nitric Acid
- Strong acid – fully ionises in water.
- Highly oxidising – can turn metals into nitrates.
- Fumes white vapour in humid air.
What is Sulphuric Acid?
Sulphuric acid (H2SO4) is a thick, oily liquid that’s one of the most widely used chemicals on Earth. It’s the “workhorse” of industry – from making batteries to cleaning metals.
Industrial Preparation of Sulphuric Acid (Contact Process)
The contact process begins with sulphur (S) or sulphur dioxide (SO2) and ends with the acid.
Key steps:
- Burn sulphur in air: S + O2 → SO2
- Oxidise SO2 to sulphur trioxide (SO3) using a vanadium(V) oxide catalyst: 2SO2 + O2 → 2SO3
- Absorb SO3 in water to give sulphuric acid: SO3 + H2O → H2SO4
Think of it like making a syrup: you first melt the sugar (sulphur), then add heat (oxygen) to get a thicker mixture (SO3), and finally dilute with water to get the final drink (acid).
Properties of Sulphuric Acid
- Very strong acid – doesn’t fully ionise but is highly corrosive.
- Dehydrating agent – can pull water out of other substances (like turning sugar into carbon).
- Viscous, oily liquid; boils at 337 °C.
Comparison of Ammonia, Nitric Acid & Sulphuric Acid
| Property | Ammonia (NH3) | Nitric Acid (HNO3) | Sulphuric Acid (H2SO4) |
|---|---|---|---|
| Physical state (room temp.) | Gas | Liquid | Liquid |
| Acidic/Basic | Basic (forms NH4OH) | Strong acid | Strong acid |
| Major industrial use | Fertiliser (urea), refrigerant | Fertiliser (ammonium nitrate), explosives | Fertiliser (ammonium sulphate), batteries, detergents |
| Key preparation method | Haber‑Bosch (N2 + H2) | Ostwald (NH3 → NO → NO2 → HNO3) | Contact (S → SO2 → SO3 → H2SO4) |
Quick Revision Bullets
- Ammonia: NH3, gas, basic, made by Haber‑Bosch.
- Nitric acid: HNO3, liquid, strong oxidising acid, made by Ostwald process.
- Sulphuric acid: H2SO4, liquid, strong dehydrating acid, made by Contact process.
📝 Likely Exam Questions
- Write the balanced equation for the industrial preparation of ammonia.
Answer: N2 + 3H2 → 2NH3 (over Fe catalyst, 150‑200 atm, 400‑500 °C). - Explain why nitric acid is called an oxidising acid.
Answer: It contains the nitrate ion (NO3⁻) which can accept electrons from other substances, turning them into nitrates while the acid itself is reduced to nitrogen oxides. - List two uses of sulphuric acid in industry.
Answer: (i) Manufacture of fertilizers like ammonium sulphate, (ii) Production of lead‑acid batteries. - Describe one advantage of the Contact process over the older lead chamber process.
Answer: The Contact process uses a vanadium(V) oxide catalyst, giving a higher conversion efficiency of SO2 to SO3 and thus higher acid yield. - Compare the physical states of ammonia, nitric acid and sulphuric acid at room temperature.
Answer: Ammonia is a gas, while both nitric acid and sulphuric acid are liquids.