Given: For Oxygen

P=100 kPa (abs)(Pressure)

T=$25^0 C=25+273=298K (Temperature)$

$R=260J/kg.K (Ideal \ gas \ constant)$

k=1.4 (Adiabatic constant)

To find:

c(Speed of sound)

For Oxygen at the given temperature and pressure, we know that the sound in oxygen is given by

c=$\sqrt{\frac{kP}{ρ}}$

But, By Ideal gas equation

$PV=mRT$

$\frac{P}{ρ}=RT$

Hence,

$c=\sqrt{kRT}$

c=$\sqrt{1.4(260)(298))}$

c=$\sqrt{1.4(260)(298))}$

c=329.35 m/s … this is the velocity of sound in oxygen at the given pressure and temperature.