Science with Tara

Ammonia is an important gas in Chemistry. In this lesson, we will learn its properties, uses, industrial preparation, and bonding.

Physical Properties of Ammonia

Ammonia is a colourless gas at room temperature and pressure.

Chemical Properties of Ammonia

Ammonia as a Weak Alkali

Ammonia dissolves in water to form weak alkali.

Equation:
NH₃ (g) + H₂O (l) ⇌ NH₄⁺ (aq) + OH^– (aq)

A weak alkali ionises partially in aqueous solution. It is the hydroxide ions (OH^–) formed that gives aqueous ammonia its alkaline properties.  

We use ⇌ to represent partial ionisation of weak alkalis. Do not use arrows like ⇄ and ⇿.

Industrial Preparation of Ammonia

Haber Process

Ammonia is manufactured industrially by the Haber Process.

Uses of Ammonia

Ammonia is used to make fertilisers, explosives, dyes, household cleaners and nylon.

Ammonia is an important raw material in the manufacture of nitric acid (HNO₃) via Ostwald Process.

Ostwald Process (Making Nitric Acid)

The Ostwald Process is not required for IGCSE or O-Level examinations. However, it is great to know more. Hence, I will be sharing more details here.

Stage 1

Ammonia is oxidised into nitric oxide and steam. This is a highly exothermic reaction.

Equation:
4NH₃ (g) + 5O₂ (g) → 4NO (g) + 6H₂O (g)

Stage 2

Nitric oxide is further oxidised to form nitrogen dioxide, which is then dissolved in water to form nitric acid.

Equations:
2NO (g) + O₂ (g) → 2NO₂ (g)
3NO₂ (g) + H₂O (l) → 2HNO₃ (aq) + NO (g)

Nitric acid obtained is in diluted form. It can be concentrated to the required strength by fractional distillation. Nitric oxide gas is recycled.

Dot and cross diagram of Ammonia

Ammonia (NH₃) consists of one nitrogen atom and three hydrogen atoms joined by covalent bonds.

Nitrogen atom has 7 electrons. Electronic configuration of nitrogen is 2, 5.

Hydrogen has 1 electron. Electronic configuration of hydrogen is 1.

Nitrogen atom shares 1 electron with each hydrogen atom. Nitrogen achieves stable noble gas octet electronic configuration of 2,8. Hydrogen achieves stable noble gas duplet electronic configuration of 2.