Reversable reactions, industrial processes and important chemicals Flashcards
What is meant by a reversible reaction?
The products are capable of reacting to produce the original reactants again.
What is the Haber process?
the production of ammonia
What is the chemical formula for the Haber process?
nitrogen + hydrogen <=> ammonia
N2 + 3H2 <=> 2NH3
Why is the Haber process being reversible a problem?
They do not want the ammonia to break down back into nitrogen and hydrogen again.
What are the 3 conditions needed to produce as much ammonia as possible?
- moderately high temperature (450*)(gives 15% yield)
- high pressure (200 atm)
- an iron catalyst (speed up reaction)
Why is high pressure used?
High pressure always pushes the reaction in the direction of the smallest umber of molecules.
As 2 molecules of ammonia are produced by the combination of one molecule of nitrogen and three of hydrogen, the pressure favours the productions of ammonia.
Why is the temperature for the Haber process not too high?
High temperature favors the backward reaction.
The forward reaction is exothermic, the backwards reaction is endothermic.
High temperatures always favours the endothermic reactions.
Why is the temperature for the Haber process not too low?
below 400c the reaction rate is very slow and it would take a long time to produce significant amounts of ammonia.
What is the test for ammonia?
ammonia gas turns red damp litmus paper blue, as it is the only gas which is alkaline.
What is the smell of ammonia?
Characteristic sharp and choking smell.
What is the test for ammonia gas?
Hydrogen chloride which combines with ammonia to make ammonium chloride, which forms white smoke.
What is nitrogen used for in industry?
- nitrogen is needed by plants to make the proteins they need for growth and as ammonia contains nitrogen, ammonium compounds are used in fertilisers.
3 elements needed for plant growth?
Nitrogen, phospherous, potassium
Describe the process of eutrophication?
- fertiliser stimulates growth of plants in water
- rapid growth will form a continuous layer on surface of water
- light cannot reach the bottom of the pond and so the bottom-living plants cannot photosynthesise and die
- photosynthesis adds oxygen to the water so the oxygen levels drop and the living animals may die (?)
- lots of dead plants in water
- bacteria breaks down the bodies of the plants and grow in numbers.
- fish are very active and need oxygen which no longer exists because it being used within bacteria. `
What is the formula for ammonia nitrate?
ammonia + nitric acid = ammonium nitrate
ammonia is a base so this is a neutralisation reaction
