Physics Waves Problems?

Question

I've tried to do both of these problems but im not getting the correct answers. Any help?

A monatomic ideal gas ( = 1.67) is contained within a box whose volume is 6.0 m3. The pressure of the gas is 3.00 105 Pa. The total mass of the gas is 3.5 kg. What is the speed of sound in the gas?

2)

A 3.49 rad/s (33 1/3 rpm) record has a 4.00 kHz tone cut in the groove. If the groove is located 0.130 m from the center of the record what is the "wavelength" in the groove?

But how do I get the temperature? I try using PV=nRT but I dont' have the number of moles.

v_sound =sqrt(yPV/m)

Thanks!

Answer 1

v_sound = sqrt ( γ R T / M )

γ is the adiabatic constant of the gas ( 1.67 )
R is the universal gas constant ( 8.314 J / mole-K )
T is the temperature in Kelvins
M is the molecular mass of the gas in kg / mole.

Answer will be in m/s.

The period of a 4000-Hz tone is 1 / 4000. The distance traveled by the record needle during that time is r ω t where r is the radius, ω the angular velocity, and t the period just computed.