Making Ammonia

Question 1

In the Haber process, where do they get the nitrogen, N2 and the hydrogen, H2?

Answer 1

Nitrogen from the air. Hydrogen from the cracking of oil fractions or from natural gas.

Question 2

Construct the word and the balanced symbol equation for the Haber process.

Answer 2

nitrogen + hydrogen <==> ammonia N2 + 3H2 <==>2NH3

Question 3

Describe the conditions used when ammonia is made in the Haber process.

Answer 3

Iron catalyst, high pressure, temperature in the region of 450°C.

Question 4

What happens to the un-reacted gases?

Answer 4

Un-reacted nitrogen and hydrogen are recycled.

Question 5

Explain the pressure used in the Haber process.

Answer 5

High pressure increases the percentage yield of ammonia.

Question 6

Explain the temperature used in the Haber process.

Answer 6

High temperature decreases the percentage yield of ammonia but high temperature gives a high rate of reaction; so 450°C is an optimum temperature to give a fast reaction with a sufficiently high percentage yield

Question 7

Explain the catalyst used in the Haber process.

Answer 7

Iron catalyst increases the rate of reaction but does not change the percentage yield

Question 8

What five things affect the cost of making a new substance?

Answer 8

1. Plant (equipment)
2. Labour costs (wages)
3. Energy costs (gas and electricity)
4. Materials (cost of starting or raw materials)
5. Speed, (cost of catalyst).

Question 9

Describe how pressure affects the cost of making a new substance.

Answer 9

The higher the pressure the higher the plant cost

Question 10

Describe how temperature affects the cost of making a new substance.

Answer 10

The higher temperature the higher the energy cost

Question 11

Describe how catalysts affect the cost of making a new substance.

Answer 11

Catalysts reduce costs by speeding up the reaction which means less time using energy

Question 12

Describe how recycling can affect the cost of making a new substance.

Answer 12

When un-reacted starting materials are recycled costs are reduced

Question 13

How can you reduce staffing costs?

Answer 13

Automation reduces the wages bill

Question 14

Explain how economic considerations determine the conditions used in the manufacture of chemicals:

Answer 14

1. rate must be high enough to give a sufficient daily yield of product
2. percentage yield must be high enough to give a sufficient daily yield of product
3. a low percentage yield can be accepted if the reaction can be repeated many times with recycled started materials
4. Optimum conditions used that give the lowest cost rather than the fastest reaction or highest percentage yield.

Question 15

Give some of the uses of ammonia.

Answer 15

The manufacture of fertilisers and the manufacture of nitric acid. Household cleaners.