Question

What volume of of O2 would be required to react with excess SO2 at STP to produce 0.5 mole of SO3 by the reaction
SO2 + O2 ---> SO3

Answer 1

2SO₂ + O₂ → 2SO₃

n(O₂) = $\frac{1}{2}$ n(SO₃) = 0.25 mol

1 mol of any gas occupies 22.4 L of volume at STP.

V(SO₂) =$0.25\; mol \times 22.4 \;mol/L = 5.6\; L$