The Haber Process

Question 1

What does the Haber process produce? What is this used for?

Answer 1

Ammonia (NH₃) used to make fertilisers

Question 2

What is the equation for the Haber process? (Word and symbol)

Answer 2

Nitrogen + Hydrogen = Ammonia

N₂ (g) + 3H₂ (g) —> 2NH₃ (g) + Heat

Question 3

Where is nitrogen obtained from?

Answer 3

Easily from the air which is 78% nitrogen (21% oxygen)

Question 4

Where is hydrogen obtained from?

Answer 4

Comes from natural gas or from other sources like crude oil.

Question 5

What are the industrial conditions for making ammonia?

Answer 5

Pressure - 200 atmospheres
Temperature - 450°C
Catalyst - Iron

Question 6

Describe the reaction (reversible)

Answer 6

Some of the reactants react to form ammonia. Because the reaction is reversible ammonia breaks down again into nitrogen an hydrogen. The reaction reaches an equilibrium.

Question 7

Higher pressures favour the [ ] reaction. Therefore…

Answer 7

Forward

The pressure is set as high as possible to give thee best % yield, without making the plant too expensive to build .

Question 8

The forward reaction is [ ], which means that increasing the temperature will actually move the equilibrium the wrong way (away form [ ] and towards the [ ]). So the yield of ammonia would be greater at [ ] temperatures.

Answer 8

exothermic
ammonia
reactants
lower

Question 9

What is the issue with low temperatures? So what do they do…

Answer 9

Lower rate of reaction.

They increase the temp anyway to get a much faster reaction (better to get less yield quickly than lots of yield slowly)

Question 10

The 450°C is a [ ] between [ ] and speed of reaction.

Answer 10

Compromise

Maximum yield

Question 11

The ammonia is formed as a [ ] but it cools in the [ ] it liquefies and is removed.

Answer 11

Gas

Condenser

Question 12

What happens to the unused Hydrogen and Nitrogen?

Answer 12

They are recycled so nothing is wasted

Question 13

The [ ] catalyst speeds up the reaction and keeps the [ ] down.

Answer 13

Iron

Cost

Question 14

Describe the use of the iron catalyst?

Answer 14

Makes the reaction go faster which gets it to the equilibrium position faster. (Doesn’t affect the position of the equilibrium).
Without the catalyst the temp would have to be raised even further to get a quick enough reaction, and that would reduce the % yield even further.