As we know that one mole of any Ideal gas at standard temperature and pressure occupies exactly 22.4 dm³ volume.
Solution for problem:
When 1 mole Neon (Ne) occupies 22.4 dm³ at STP then the volume occupied by 2.25 moles of Neon is calculated as,
= ( 22.4 dm³ × 2.25 moles ) ÷ 1 mole
= 50.4 dm³ 1dm³ = 1 L
Result:
So, 50.4 dm³ (Liter) volume will be occupied by 2.25 moles of Neon gas if it acts ideally at STP.