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
