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Flashcards in C2e Deck (10):
1

What happens in the Haber process?

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

2

How is ammonia made in the Haber process?

nitrogen + hydrogen = ammonia
iron catalyst
high pressure
temperature in the region of 450oC
unreacted nitrogen and hydrogen are recycled

3

What is the balanced symbol equation for the manufacture of ammonia in the Haber process?

N2 + 3H2 = 2NH3

4

What are the conditions used in the Haber process?

High pressure increases the percentage yield of ammonia. High temperature decreases the percentage yield of ammonia and gives a high rate of reaction. 450oC 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.

5

What does the cost of making a new substance depend on?

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).

6

How do different factors affect the cost of making a new substance?

`The higher the temperature the higher the energy cost.
When unreacted starting materials are recycled costs are reduced.
Automation reduces the wages bill, by reducing the number of people involved.
The higher the pressure, the higher the plant cost.
Catalyst reduces cost by increasing the rate of reaction.

7

How do economic considerations determines the conditions used in the manufacture of chemicals?

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 use that give the lowest cost rather than the fastest reaction or highest percentage yield.

8

What does a reversible reaction proceed in?

Both directions.

9

What are some of the uses of ammonia?

Manufacture of fertilisers and manufacture of nitric acid.

10

What is the importance of ammonia in relation to world food production?

It's a key ingredient of many fertilisers, which increase the crop yield so crops can grow faster and bigger, and more people can be fed.