speed of sound in helium?

Question

Compute the velocity of sound in helium at 700 Celsius and the molecular mass is 4.00 g/mol

Answer 1

C=sqrt(a' R T)
•R (287.053072 J•kg-1•K-1 for air) is the gas constant specific for air: This is the universal gas constant R * (units of J•mol-1•K-1), divided by the molar mass n of air, a notation common in aerodynamics. In other words, R = R * / n.
•a' is the adiabatic index (1.40 for air). for helium it must be computed as a ratio between specific heat capacity at constant pressure (cP) to its specific heat capacity at constant volume (cV).
•T is the absolute temperature in degrees Kelvin