C15 - Using our resources (Part 2 - Haber Process and Fertilisers)

Question 1

Common use of ammonia

Answer 1

Makes nitrogen based fertilisers

Question 2

Equation for the haber process

Answer 2

nitrogen + hydrogen ⇌ ammonia
N₂ + 3H₂ ⇌ 2NH3

Question 3

Source for nitrogen for the haber process

Answer 3

Extracted from the air

Question 4

Source for hydrogen in the haber process

Answer 4

Reacting methane with steam

Question 5

Describe the steps in the haber process

Answer 5

• N₂ and H₂ put into reaction vessel
• They are passed over an iron catalyst at 450°c and 200 atmopsheres pressure
• Some formation of ammonia
• This is then cooled, liquefied and removed
• The unreacted N₂ and H₂ and recycled back into the reaction vessel

Question 6

Optimum conditions for the Haber process

Answer 6

Low temp - causes equilibira to shift in the right, exothermic direction producing more ammonia
High pressure - shift equilibria to side with fewer molecules, increasing yield of ammonia

Question 7

Why are 450c and 200 atmospheres chosen

Answer 7

• Conditions are a compromise - they allow a relatively high yield, relatively high rate of reaction and cheaper cost

Question 8

Problems with the optimum conditions for the Haber process

Answer 8

Low temp - causes rate of reaction to be too slow + reduces effectiveness of iron catalyst

High pressure - high enercy cost to compress the gas and expensive to have equipment that can withstand high pressure