Sulphuric Acid Flashcards
Raw materials in contact process
Sulphur- from sulphur deposits beneath the ground, sulphide ores or hydrogen sulphide from natural gas
Air- from the atmosphere
Water
How is Sulphur obtained?
The sulphur is obtained by the desulphurisation of natural gas or bouncing of volatile sulphides.
Conversion of SO2 - SO3
The sulphur dioxide is mixed with the oxygen and the mixture is compressed to a pressure of 2-3 atm and passed over a catalyst of vanadium (V) oxide at 450oC.
Under these conditions, there is a 98% conversion of SO2 to SO3.
2SO2 (g) + O2 (g) ⇌ SO3 (g)
Conversion of SO3 - oleum
The So3 is then allowed to react with sulphuric acid to form oleum.
SO3 (g) + H2SO4 (aq) → H2S2O4 (l)
Dilution of The SO3
The SO3 is not allowed to combine with water directly since the reaction is highly exothermic.
The heat produced will vaporize the acid formed, converting it to a mist, which will be difficult to condense.
H2S2O4 (l) + H2O (l) → H2SO4 (aq)
Conditions for pressure in contact process
There is a decrease in volume
At greater pressures, the higher the yield of SO3
However high pressures aren’t used because the yield of SO3 is already high at low pressures
Effect of temperature on contact process
Sulphur trioxide production is favoured by lower temperature.
Due to the reaction being exothermic, an increase in temperature → Kp value decreases → decreases the yield of forward reaction.
Temperature range is between 450-580oC.
Effect of catalyst on contact process
Does not affect yield of sulphuric trioxide but increases rate of reaction
Works best at 410°C
Uses of sulphuric dioxide
A good reducing agent and is used as a bleaching agent in manufacture of wool, straw and paper.
Used as an antioxidant in the preservation of food, wine, and soft drinks. Preserves food by preventing growth of molds and bacteria.
Uses of sulphuric acid
Added to calcium fluorophosphate rocks → phosphoric acid → phosphate fertilizers
To make ammonium sulphate (fertiliser)
As a cleaning agent for metal surfaces
As he electrolyte in lead/ acid car batteries
As a catalyst in various chemical reactions
To make detergents
Vulcanisation
Adding sulphuric to rubber to make tires harder and make rubber less sticky
Sulphur powder
Used as fungicide for dusting on plants
Carbon disulphide
Used for making polymers, rayon and cellophane
Impacts of sulphuric acid industry
Can cause acid rain because it is toxic
Can acidify rivers and lakes → cause death of animals and plants which are acid sensitive
Can cause acidification of soils → loss of minerals by leaching
Sulphur dioxide in the atmosphere → irritation of eyes and throat
Acid aerosols containing sulphur dioxide is a fire hazard
Contact of metals with sulphuric acid spill → liberation of hydrogen gas → explode and cause fires
Eutrophication through fertilizers
