The balanced chemical equation for sulfur reacting with oxygen to produce sulfur trioxide is:

2 S + 3 O₂ → 2 SO₃

Here's a breakdown of the equation:

* S: Sulfur (reactant)

* O₂: Oxygen (reactant)

* SO₃: Sulfur trioxide (product)

Explanation:

* The equation is balanced because there are equal numbers of sulfur (S) and oxygen (O) atoms on both sides of the equation.

* The coefficient "2" in front of sulfur and sulfur trioxide ensures that there are two sulfur atoms on each side.

* The coefficient "3" in front of oxygen ensures that there are six oxygen atoms on each side.