Making ammonia

Question 1

in the haber process what is ammonia made from?

Answer 1

ammonia is made from nitrogen from the air and hydrogen that comes from the cracking of oil fractions or from natural gas

Question 2

Describe that the cost of making a new substance

depends on:

Answer 2

• price of energy (gas and electricity)
• cost of starting materials
• wages (labour costs)
• equipment (plant)
• how quickly the new substance can be made
(cost of catalyst).

Question 3

Recall some of the uses of ammonia

Answer 3

• manufacture of fertilisers

* manufacture of nitric acid

Question 4

what is a reversible reaction?

Answer 4

it proceeds in both directions

Question 5

Describe how ammonia is made in the Haber

process:

Answer 5

• nitrogen + hydrogen ammonia
• iron catalyst
• high pressure
• temperature in the region of 450°C
• unreacted nitrogen and hydrogen are recycled.

Question 6

Construct the balanced symbol equation for the

manufacture of ammonia in the Haber process

Answer 6

N2 + 3H2 -> 2NH3

Question 7

Describe how different factors affect the cost of

making a new substance

Answer 7

• the higher the pressure the higher the plant cost
• the higher the temperature the higher the energy
cost
• catalysts reduce costs by increasing the rate of
reaction
• when unreacted starting materials are recycled
costs are reduced
• automation reduces the wages bill

Question 8

Recognise the importance of ammonia in relation to

world food production.

Answer 8

it allows much more food to be grown

Question 9

Explain the conditions used in the Haber process:

Answer 9

• high pressure increases the percentage yield of
ammonia
• high temperature decreases the percentage yield
of ammonia
• high temperature gives a high rate of reaction
• 450°C is an optimum temperature to give a fast
reaction with a sufficiently high percentage yield
• catalyst increases the rate of reaction but does
not change the percentage yield.

Question 10

Explain how economic considerations determine the

conditions used in the manufacture of chemicals:

Answer 10

• rate must be high enough to give a sufficient daily
yield of product
• percentage yield must be high enough to give a
sufficient daily yield of product
• a low percentage yield can be accepted if the
reaction can be repeated many times with
recycled starting materials
• optimum conditions used that give the lowest
cost rather than the fastest reaction or highest
percentage yield