C15.5 Making ammonia - the Haber process Flashcards
What are the use of fertilsers?
To replenish nutrients needed by the crops
Most fertilisers contain nitrogen
Why do plants need nitrogen?
To grow - as it is one of the elements they need to make proteins
Why do farmers need fertilisers to replace nitrogen and other nutrients in the soil?
As crop grows it absorbs nitrogen in the form of soluble nitrate ions from the soil through their roots
Farmer harvest the crop - so most parts of the plant are not allowed to rot back into the soil
So the nitrogen absorbed by the soil during growth is not all replaced by the natural cycling of nitrogen
Why can’t plants use the nitrogen in the air?
The gas is insoluble in water and most plants can only absorbs a soluble form of nitrogen
What is fixing nitrogen?
Turning nitrogen gas from the air into nitrogen compounds that plants can absorb in the solution through their roots
What is the Haber process?
Provides a way of turning nitrogen in the air into ammonia
What are the raw materials for the production of ammonia?
Nitrogen from the air
Hydrogen mainly from natural gas such as Methane
How is ammonia made?
Nitrogen and hydrogen are purified
Passed over an iron catalyst at high temperature about 450 degrees and high pressure about 200 atmospheres
How is the ammonia removed?
By cooling the gases so that the ammonia liquefies - can be separated from the unreacted nitrogen gas and hydrogen gas
Unreacted nitrogen and hydrogen are recycled
Why are the unreacted hydrogen and nitrogen are recycled?
Saves money and increases the effective (overall) yield
Why is iron used?
As a catalyst to speed the rate of reactin
