The Industrial Manufacture of Chemicals Flashcards
What is produced in the contact process?
- Sulphuric acid
What are the uses of sulphuric acid?
- Most used industrial acid
- Lead acid batteries
- Refining ore
- Waste water purification
- Fertiliser
- Detergent
- Paint
How is sulphuric acid used in the manufacture of detergents?
Used to make sulphonate products
How is sulphuric acid used in the manufacture of fertiliser?
Reacted to make:
- Phosphates soluble to plants
- Ammonia easier to handle
How is sulphuric acid used in the manufacture of paint?
Reacted with titanium ore to make a main pigment in paint
What are the four steps of the Contact Process?
- Make sulphur dioxide
- Convert sulphur dioxide to sulphur trioxide
- Dissolve sulfur trioxide in concentrated sulfuric acid to form liquid oleum
- Oleum is diluted with measured amounts of water to form concentrated sulfuric acid
What are the two methods of making sulphur dioxide?
- Burn sulphur in an excess of air
S (s) + O₂ (g) → SO₂ (g) - Heat sulphides in an excess of air
4FeS₂ (s) + 11O₂ (g) → 2Fe₂O₃ (s) + 8SO₂ (g)
What is the equation for making sulphur trioxide?
What are the required conditions?
2SO₂ (g) + O₂ ⇌ 2SO₃
ΔH = -ve
Catalyst: Vanadium (V) oxide, V₂O₅
Temperature: 400-450 ˚C
Pressure: 1-2 atm
Why is a temperature of about 450˚C used in the making of sulphur trioxide?
It is a compromise between percentage yield of sulphur trioxide and rate of reaction
Why is a low pressure used in the making of sulphur trioxide?
Lowers the cost of production
Why isn’t sulphuric acid made by dissolving sulphur trioxide in water?
The reaction produces fumes which:
- Are dangerous
- Reduce the yield of acid obtained
How is sulphuric acid made from sulphur trioxide?
- Dissolve SO₃ in sulphuric acid to form oleum
SO₃ (g) + H₂SO₄ (l) → H₂S₂O₇ (l) - Dissolve oleum in water
H₂S₂O₇ (l) + H₂O (l) → 2H₂SO₄ (l)
What is produced from the Haber process?
Ammonia
What is the main use of ammonia?
Fertilisers for crops - used for the food production for half the world’s population
Give reasons why it is important for farmers to use fertilisers on their land
- Provides essential plant nutrients
- Increases the yield of crops
- Replaces nutrients removed by growing plants
What is the equation for the Haber process? Is it exothermic or endothermic?
N2 (g) + 3H₂ (g) ⇌ 2NH₃ (g)
Exothermic
What raw materials are used to supply the hydrogen and nitrogen for the Haber process?
- Hydrogen*: from natural gas or cracking hydrocarbons
* Nitrogen*: air
How are the unreacted gases separated from the ammonia formed?
The reaction mixture is cooled until ammonia liquefies and can be removed
What happens to any unreacted reactants in the Haber process?
They are recycled. Continual recycling leads to an overall conversion rate of about 98%
Looking at the equation, describe and explain conditions in temperature and pressure which would favour a high yield of ammonia:
N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)
ΔH = -91 kJ/mol
- Temperature*: low - forwards reaction releases heat to oppose the low temperature
- Pressure*: high - fewer moles on RHS
What are the actual conditions used for the Haber process?
- Temperature*: 400-450 ˚C
- Pressure*: 200 atm
- Catalyst*: iron catalyst
Why are the compromise conditions for temperature and pressure in the Haber process used?
Temperature: higher temperatures lead to a faster rate of reaction despite lower % yield of ammonia
- Pressure*
- high building costs - equipment has to be strong to withstand the pressure
- using high pressures increases the running costs of the plant
- safety aspects
When using HCl, what is the main danger? How can this be mitigated when using it in experiments?
It is corrosive and can cause burns
- Wear safety gloves
- Wear eye protection
- Place bung in the end of the tube
