SULPHURIC ACID, H2S04
- The process is called the ‘contact process’. The starting material is sulphur dioxide, obtained from burning sulphur in air, or as a by-product from roasting metal ores.
- The sulphur dioxide is mixed with more air, dried and freed from dust.
- The mixture is passed over a catalyst (usually vanadium(V) oxide) at 450°C at a pressure of around 2 atmospheres.
- This converts 90% of the sulphur dioxide into sulphur trioxide - reaction is reversible.
- The sulphur trioxide is dissolved in concentrated sulphuric acid to form oleum, H2S2O7. Although sulphur trioxide will react directly with water to form sulphuric acid it tends to form troublesome mists, so it is better to dissolve it into concentrated sulphuric acid and dilute it down later.
- It is far safer to add the concentrated acid to the water.
Uses of sulphuric acid:
- used in the manufacture of chemicals (e.g. fertilisers, paints, dyes, plastics, etc.)
- used as battery acid in the lead-acid batteries used in cars.
Chemical properties of sulphuric acid:
- tendency to absorb water - used as a drying agent for gases.
- removes the water of crystallisation for copper(II) sulphate.
- used to displace other acids from their salts.
- acts as a typical strong acid - reacts with alkalis, basic oxides, carbonates and more reactive metals.
That is all!