In a longitudinal wave, the particles move in the same direction as the wave moves. In a transverse waves, the particles move perpendicular to the motion of the wave.
Q 6.4
Longitudinal.
Q6.5
You need to know the speed of sound.
Q6.6
Helium is the second lightest gas, and is much less dense than air. Speed of sound goes inversely with the square root of density.
P6.1
P6.5
P6.6
P6.10
