**The balanced chemical equation for the decomposition of sulfuric acid to form sulfur trioxide gas and water is:

**

2 H2SO4 (l) → 2 H2O (g) + 2 SO3 (g)

In this reaction, two moles of sulfuric acid (H2SO4) decompose to form two moles of water (H2O) and two moles of sulfur trioxide (SO3) gas.