Argon is often used for storing chemicals because it is a noble gas and pretty much totally nonreactive. Nitrogen is also a possible answer, as it mostly doesn't reactive with phosphorus and is more readily available.
A. The gas will diffuse from the more concentrated are to the least concentrated.
The intensity of the sound will increase more as the energy of the sound wave increases.
I hope this helps you:)
Energy
It travels in the form of energy waves