Question

How can sulphuric acid be prepared from sulphur?

Answer 1

Sulphuric acid is prepared from elemental sulphur in three chemical steps during the Contact process:

1. Burning Sulphur: Sulphur is burned in dry air to form sulphur dioxide.

\[\ce{S + O2 -> SO2}\]

2. Catalytic Oxidation: SO₂ reacts with oxygen over a catalyst to form sulphur trioxide.

\[\ce{2SO2 + O2 <=> 2SO3}\]

3. Absorption and Dilution: SO₃ dissolves in concentrated acid to form oleum, which is diluted with water.

\[\ce{SO3 + H2SO4 -> H2S2O7 ->[+H2O] 2H2SO4}\]