An ideal gas having density 1.7×10−3gcm−3 at a pressure 1.5×105 Pa is filled in a Kundt tube. When the gas is resonated at a frequency of 3.0 kHz, nodes are formed at a separation of 6.0 cm. Calculate the molar heat capaticies Cp and Cv of the gas.
P = 1.7×10−3g/cm3
= 1.7k/gm3
P = 1.5×105 Pa
R = 8.3 J/mol 1-K,
F= 3.0 KHz
Node separation in a Kundt's tube
= 12=6cm
l = 12 cm = 12 ×10−2m
So, V = ft = 3 ×103×12×10−2m
= 360 m/s
We know, speed of sound = √γpp
or V2=γpp
∴γ=v2pp=(360)21.71.5×105
= 1.4688
But Cv=Rγ−1=8.30.4688
= 17.71 J/mol-K