Answer:
4.48 dm^3
Explanation:
As given in the problem, the conversion factor for the molar volume of all gases is 22.4 dm^3/mole at STP. A mole of all ideal gases will occupy 22.4 liters (dm^3). Calculate the moles of hydrogen contained in 0.4 grams of the gas by dividing the mass by the molar mass of H2. H2 has a molar mass of 2 grams/mole.
(0.4 g)/(2 grams/mole) = 0.2 moles H2
(0.2 moles H2 at STP)*(22.4 dm^3/mole at STP) = 4.48 dm^3 (4.48 liters at STP)
Nitrous oxide will stay in the atmosphere the longest.
