2 SO₂ + O₂ → 2 SO₃

From the balanced equation, we can see that:

* 2 moles of SO₂ react with 1 mole of O₂.

Therefore, to find out how many moles of O₂ are needed to react with 3.6 moles of SO₂, we can set up a proportion:

(2 moles SO₂) / (1 mole O₂) = (3.6 moles SO₂) / (x moles O₂)

Solving for x:

x moles O₂ = (3.6 moles SO₂) * (1 mole O₂) / (2 moles SO₂)

x = 1.8 moles O₂

Therefore, 1.8 moles of O₂ are required to react with 3.6 moles of SO₂.