Haber And Contact Flashcards
(25 cards)
What is the balanced chemical equation for the Haber process?
N₂(g) + 3H₂(g) ⇌ 2NH₃(g) (ΔH = –93 kJ/mol)
The equation represents the synthesis of ammonia from nitrogen and hydrogen.
What are the typical conditions used in the Haber process?
200 atmospheres (20 MPa), 450°C, and an iron catalyst.
These conditions optimize the yield and rate of ammonia production.
Why is a pressure of 200 atmospheres used in the Haber process?
Higher pressure increases yield but is hazardous and expensive; 200 atm is a compromise.
The balance between safety, cost, and yield determines this choice.
Why is a temperature of 450°C used in the Haber process?
It provides a reasonable yield and fast rate, despite a higher yield being favoured at lower temperatures.
The rate of reaction increases with temperature, but yield decreases.
Why is an iron catalyst used in the Haber process?
It increases the rate of reaction and works efficiently above 400°C.
Catalysts lower the activation energy needed for the reaction.
What happens to unreacted nitrogen and hydrogen in the Haber process?
They are recycled back into the reactor to improve yield.
Recycling unreacted gases maximizes resource efficiency.
What is the overall yield of ammonia when recycling is included?
Around 97%.
This high yield is a result of the recycling process.
What is the effect of increasing pressure on the equilibrium yield of ammonia?
It increases the yield.
According to Le Chatelier’s principle, increasing pressure shifts the equilibrium towards the side with fewer moles of gas.
What is the effect of increasing temperature on the equilibrium yield of ammonia?
It decreases the yield.
Higher temperatures favour the endothermic direction of the reaction.
What is the effect of using an iron catalyst on the Haber process?
It increases the rate of reaction without affecting yield.
Catalysts speed up reactions but do not change the equilibrium position.
What is a possible future use for ammonia as discussed in the textbook?
As a fuel for vehicles like ammonia-fuelled cars and jets.
Ammonia’s potential as a clean fuel source is being explored.
What is the overall aim of the Contact process?
To make sulfuric acid from sulfur, oxygen, and water.
This process is crucial for producing sulfuric acid, a key industrial chemical.
What are the three raw materials used in the Contact process?
- Sulfur (or sulfur dioxide)
- Oxygen (air)
- Water
These materials are essential for the synthesis of sulfuric acid.
What are the three main stages of the Contact process?
- Sulfur burns in air to form sulfur dioxide.
- Sulfur dioxide reacts with oxygen to form sulfur trioxide.
- Sulfur trioxide reacts with water to form sulfuric acid.
Each stage is crucial for the overall production of sulfuric acid.
What is the balanced equation for stage 1 of the Contact process?
S(s) + O₂(g) → SO₂(g) (ΔH = –297 kJ/mol)
This stage involves the combustion of sulfur.
What is the balanced equation for stage 2 of the Contact process?
2SO₂(g) + O₂(g) ⇌ 2SO₃(g) (ΔH = –144 kJ/mol)
This stage involves the oxidation of sulfur dioxide.
What are the typical conditions for stage 2 of the Contact process?
2 atmospheres pressure (200 kPa), 450°C, vanadium(V) oxide catalyst (V₂O₅).
These conditions optimize the reaction for producing sulfur trioxide.
What is the effect of increasing pressure on the yield of sulfur trioxide?
It increases the yield.
Similar to the Haber process, increasing pressure shifts the equilibrium.
What is the effect of increasing temperature on the yield of sulfur trioxide?
It decreases the yield.
Higher temperatures favour the reverse reaction.
Why is 450°C used in the Contact process despite the lower yield?
It gives a good rate of reaction and a reasonable yield.
This temperature is a compromise between rate and yield.
Why is a vanadium(V) oxide catalyst used in the Contact process?
It increases the rate of reaction without affecting the yield.
Catalysts are essential for improving reaction kinetics.
What is the balanced equation for stage 3 of the Contact process?
H₂SO₄(l) + SO₃(g) → H₂S₂O₇(l); then H₂S₂O₇(l) + H₂O(l) → 2H₂SO₄(aq)
This stage involves the formation of sulfuric acid from sulfur trioxide.
Why is sulfur trioxide not added directly to water in stage 3?
It would create a hazardous acidic mist; it’s first absorbed in concentrated sulfuric acid.
This method ensures safety and efficiency in the reaction.
What is one advantage of using sulfur dioxide from waste gases?
It reduces pollution from industrial processes.
Utilizing waste gases contributes to environmental sustainability.
