the haber process Flashcards
(7 cards)
what the hellyaber process
Makes ammonia on a very large scale from nitrogen and hydrogen
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
conditions chosen for haber process
pressure of 200 atmospheres (20 MPa)
temperature of 450
iron catalyst
butunder these conditions, equilibrium yield of ammonias about 30 percent mate..
what factors determine chosen temp (haber)
forward reaction is exothermic so backward reaction is endothermic
if temp increases, equilbrium position moved to the left + equilbrium yield of ammonia decreases
high equilibrium yield favoured by a low temp
temp chosen (450) is compromise,low enough for reasonable yield but high enough to achieve reasonable rate of reaction
also, iron catalyst works more efficiently above 400
what factors determine pressure (haber)
in balanced equation, 4 mol on left but only 2 mol on right
if pressure increased, equilibrium position moves to the right, equilbrium yield of ammonia increases
HOWEVRER, it’d be hazardous and expensive to choose v high pressure
the higher equilbrium yield would NOT justify the additional costs, so 200 atmospheres chosen as compromise
what other conditions chosen (haber)
the mixture of gases leaving the reaction vessel is cooled so ammonia liquified
allows ammonia to be removed and unreacted nitrogen and hydrogen to be recycled
improved overall yield to around 97%
factors affecting manufacture
price of energy
labour costs
cost of catalyst
cost of starting materials (reactants)
cost of equipment
factors affecting the above
- pressure, high pressure=higher cost
-temp, higher temp=higher energy cost
-catalysts, can be expensive to buy but production costs reduced as they increase reaction rate
- number of people needed to operate machinery, automation reduces wages bill
- amount of unreacted material- recycling reduces costs
how haber
nitrogen from the air is reacted with hydrogen from the electrolysis of water
theyre passed over a catalyst at a temp of 4450 and pressure of 200 atm
