STUDENT SPACE · TOPIC 2

Ammonia manufacture and fertilisers

Explain Haber conditions and identify nutrients supplied by fertilisers.

The essentials

Nitrogen comes from air. Hydrogen comes from methane. The feed ratio is 1 volume of N₂ to 3 of H₂.
Lower temperature favours ammonia but gives a slower rate. 450 °C gives a useful compromise.
Cooling condenses ammonia. Unreacted nitrogen and hydrogen return to the reactor.
Ammonium salts and nitrates supply nitrogen. NPK fertilisers provide nitrogen, phosphorus and potassium for improved growth.

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Explain why nitrogen and hydrogen are recycled.

Need a hint for Question 1?

State which direction is exothermic. Separate the effect on rate from the effect on equilibrium.

Check Question 1

Only part reacts in one pass. Recycling gives unreacted gases another opportunity to form ammonia and reduces waste.

State the Haber equation, catalyst and pressure.

Need a hint for Question 2?

Balance N and H; distinguish Haber from Contact conditions.

Check Question 2

N₂ + 3H₂ ⇌ 2NH₃; iron; 200 atm (20 000 kPa).

Which NPK elements are supplied by NH₄NO₃ and by K₃PO₄?

Need a hint for Question 3?

Read the element symbols in each formula.

Check Question 3

NH₄NO₃ supplies nitrogen. K₃PO₄ supplies potassium and phosphorus.

Use Lesson 2 in your worksheet for written practice. Your teacher will discuss those answers in class.