Haber process + fertilisers

Question 1

Haber process equation

Answer 1

N2 + 3H2 —> 2NH3 (ammonia) (+heat)

Question 2

Haber process steps

Answer 2

• get nitrogen from air and hydrogen from methane
• passed over an iron catalyst at 450 degrees with 200 atm pressure, reaches dynamic equilibrium as it is reversible
• removed as a gas but liquifies in a condenser, unused nitrogen and hydrogen are recycled
• makes ammonium nitrate (fertiliser)

Question 3

Why are the conditions as they are?

Answer 3

450 degrees is the best compromise between speed and yield
200 atm maximises yield with reasonable cost
Iron catalyst speeds up the rate but doesn’t affect yield

Question 4

NPK fertilisers

Answer 4

• more widely available, easier, don’t smell, formulated so have the right amount of each nutrient
• nitrogen, phosphorus, potassium
• salts of N P and K in the right percentages

Question 5

Ammonia reaction

Answer 5

NH3 + HNO3 —> NH4NO3

Ammonia + nitric acid —> ammonium nitrate

Question 6

Industry ammonia reaction

Answer 6

Carried out in giant vats at high concentrations, exothermic, heat used to evaporate water to make a very concentrated product

Question 7

Lab ammonia reaction

Answer 7

Much smaller scale, titration and crystallisation

Lower concentration, less heat, safer, slower

Question 8

How to get phosphate and potassium

Answer 8

Potassium chloride and potassium sulphate can be mined

Phosphate rock is mined but salts are insoluble

Question 9

Phosphate rock with acids so it can be used

Answer 9

Nitric acid —> phosphoric acid and calcium nitrate
Sulfuric acid —> calcium sulfate and calcium phosphate (mixture known as single superphosphate)
Phosphoric acid —> calcium phosphate (the product can be called triple superphosphate)