CMM: The Haber Process Flashcards
Identify and describe the industrial uses of ammonia
Ammonia is used industrially as a feedstock (raw material from which a substance or industrial process is derived) mainly for the manufacture of:
– Fertilisers (sulfate of ammonia, ammonium nitrate, urea), which are used to grow plants
where soils may be deficient in nitrogen compounds.
– Explosives (derived from nitric acid) such as TNT and nitro-glycerine.
– Fibres and plastics (e.g. nylon, rayon).
What is the formula for the Haber process and identify that is exothermic
N2 (g) + 3H2 (g) <> @2NH3 (g) + heat
The forward reaction is exothermic = -92 kj/mol
Describe the process of the Haber Process
The reactants pass through the catalytic reactor and the mixture is cooled to condense out the ammonia formed.
Unreacted gases are fed back into the catalyst chamber along with fresh reactants.
None of the reactant mixture is wasted.
The reaction goes to completion, as the reaction product is condensed out.
Explain that the use of a catalyst will lower the reaction temperature required and identify the catalyst(s) used in the Haber process
Catalyst: Magnetite (Fe3O4) which increases the rate of reaction by lowering the activation energy of reactants.
The catalyst speeds both forward and backward reaction rates equally, such that the equilibrium position is not changed, hence not affecting yields.
However, temperature require to attain a high reaction rate i lower, allowing the equilibrium to favour the products and hence increase yield. This would not be possible is temperature was used to attain an equivalent rate of reaction as it would result in a much lower yield.
Explain why the rate of reaction in the Haber Process is increased by higher temperatures
As temperature increases, particles have higher kinetic energy. This increases the frequency of collisions between reacting particles exceeding the activation energy barrier.
Hence more reactions occur and the rate of reaction is increased. The rate of both forward and reverse reactions is increased
Explain why the Haber process is based on a delicate balancing act involving reaction energy, reaction rate and equilibrium
The aim of the Haber process is to maximise yield and reaction rate, and minimise cost in order to gain maximum profit. A delicate balance between these conditions is required to achieve the most profitable yield for the least cost.
What are the conditions needed for a compromise for the Haber process?
Temperature: 400°C
A compromise temperature allows reactants to have sufficient kinetic energy to overcome the activation energy barrier while achieving a reasonable yield.
– Pressure: 250
Increasing pressure results in a greater yield, however due to economic and safety
considerations a lower pressure is used.
A high pressure requires thick-walled containers and safety valves which are expensive,
and is also unsafe as there is the risk of explosion.
– Reactants: 3:1 ratio of and
As is formed and condensed out, left-over reactants can be recycled without any build-up of one reactant.
– Catalyst: magnetite ( )
The catalyst allows lower temperatures and pressures to be used to achieve reasonable
reaction rates without a great loss in yield.
Explain why monitoring of the reaction vessel used in the Haber process is crucial and
discuss the monitoring required
Temperature and total pressure are kept in the range for optimum conversion of reactants to products:
High pressure reaction vessel: so that that the production of ammonia is safe (too high) and yield is not compromised (too low)
Temperature: if temperature is too high, yield is reduced and excessive temperature can damage the catalyst
Ratios kept 3:1 to avoid a build up of one reactant
Concentrations of oxygen, carbon monixed carbon fioxide sulfur compounds, argon and methne
Catalyst particle size to ensure it has a high surface area for abosription of nitrogen and hydrogen gases
Describe the conditions under which Haber developed the industrial synthesis of ammonia
The Haber Process was a method for producing ammonia, developed by Germany during
WW1.
- 1900’s shortage of naturally occuring nitrogen sources, especially ammonia and nitrates.
- Before invention of the Haber Process in 1914, highly depended on main source of nitrates for fertilisers and explosives came from saltpetre from Chile. However they were cut off as a result of WW1
Evaluate Haber Process significance at that time in world history
Significant because it insulated German agriculture from any harm caused by interrupted supplies
Industrial synthesis of ammonia facillitated the manufactur of fertilisers for continued food production and nitruc acid –> essential for explosives and ammunition
Allowed them to continue the war effort
