What is the chemical equation for the decomposition of sulfuric acid?

As decomposition reaction means breakdown of compounds in chemistry. Decomposition of Sulphuric acid takes place in two steps.

1. In the first step, sulphuric acid breaks down into Sulphur trioxide (SO3) and water (H2O).
1. H2SO4 (Thermal Decomposition) SO3 + H2O
2. In the second step, Sulphur trioxide breaks down into Sulphur dioxide and half molecule of O2.
1. SO3 (Catalytic Decomposition) SO2 + 1/2 O2

The physical decomposition of sulfuric acid can transpire as follows:

H2SO4 <> H2O + SO3
2H2SO4 <> 2H2O + 2SO2 + O2
H2 + H2SO4 <> 2H2O + SO2

Note: this is NOT the dissociation of sulfuric acid, i.e. the donation of a proton in a reaction with water.