Ammonia & Fertilisers Flashcards
General properties of Ammonia as a gas:
- Colourless
- Distinctive/pungent smell
- Less dense than air
- Very soluble in water to give an alkaline solution
Ammonia uses:
- Fertilisers (main product)
* Explosives
Name of process for making Ammonia?
Haber-Bosch Process
Haber process is a ____________.
Reversible Reaction
Chemical Equation for the Haber Process:
N₂ + 3H₂ ⇌ 2NH₃
The forward reaction is exothermic, and the backwards reaction is endothermic.
Conditions of the Haber Process:
- Temperature = 450 °C
- Pressure = 200 atm (atmospheres)
- Catalyst = Iron (Fe) powder form
The left over nitrogen and hydrogen is ______.
Recycled
Why is nitrogen and hydrogen recycled?
- The yield of ammonia is low
- The process requires large amounts of energy
- More efficient and increases the overall yield by doing this
Nitrogen and hydrogen are mixed in : ratio at the start of the process.
1:3
Where do you collect hydrogen?
From natural gas
Where do you collect nitrogen?
From the air
Why do many fertilisers contain N, P and K?
Three elements needed by plants so they can grow
Why is the Haber process run at 450 °C?
- Increasing the temperature favours the endothermic reaction, which is the reverse reaction, so less ammonia is produced at hotter temperatures
- At low temperatures, the reaction rate is too slow
- 450 °C is a compromise between high yield and high rate
Why is the Haber process run at 200 atmospheres pressure?
- Increasing the pressure favours the reaction that produces the fewest moles of gas - in this case the forward reaction
- Increasing the pressure increases the rate of reaction
Why is the Haber process not run at very high pressure?
High pressures are expensive (containers) and dangerous to maintain
Nitrogen makes up ____ of air.
80%
Step 1 Haber Process
Gases are scrubbed and mixed
Step 2 Haber Process
Gases are compressed (200 atm)
Step 3 Haber Process
Gas flows over bed of hot (450 °C) fine iron catalystGases are compressed (200 atm)
Step 4 Haber Process
Mixture is cooled
Step 5 Haber Process
Unreacted gas are recycled
