Question

How many degreed of freedom have the gas molecules,if under standard conditions the gas dendity is 1.3kg/m^3 and velocity of sound propagation on it is v=330m/s?

Answer 1

<v> =sqrt{3RT/M}=sqrt{3pV/m} =>
M=mRT/pV =ρRT/p.

v=sqrt {γRT/M}.
γ=C_p /C_v = (i+2)/i.
v=sqrt{9i+2)RT/iM} = sqrt{(i+2)RTp/iρRT}=
=sqrt{(i+2)p/iρ},
iρv² - ip = 2p,
i=2p/ (ρv² - p) =
=2• 1.01325• 10⁵/(1.3•330²-1.01325• 10⁵)
=4.9 ≈ 5.

i=5

Answer 2

What is the value at NTP