How much volume would 0.450 mol CO2 gas occupy?

10.08 L.

Explanation:

If we assume that CO₂ gas behaves ideally at STP (standard T (0.0 °C) and P (1.0 atm)):

It is known that 1.0 mole of ideal gas occupies 22.4 L at STP conditions.

Using cross multiplication:

1.0 mole of CO₂ gas occupies → 22.4 L.

0.45 mole of CO₂ gas occupies →? L.

∴ The volume occupied by 0.45 mole of CO₂ gas = (0.45 mol) (22.4 L) / (1.0 mol) = 10.08 L.