# Calculate velocity of sound in mixture of 1 mole He and 1mole O2 at 127 degrees Celsius .

According to Laplace formula, the speed of sound is given by

V=√γRT/M----------equation(1)

Molecular weight of mixture of gases:

M mix=(n 1M1+n 2M2)/n1+n2

=1x4+2x 32/1+2

=68/3 x 10⁻³kg/mol

As Helium is Mono atomic so

Cv=3R/2

while oxygen is diatomic [Cv=5R/2]

hence(Cv)mix=(n1 Cv1+n 2 Cv2)/n1+n2

=1x(3/2)R+ 2x(5/2)R/1+2

=13R/6

(Cp)mix=(Cv)mix +R

=13/6+R=19/6

γ mix=Cp/CV

=19R/6/13R/6

=19/13

Now substituting the values of M and γ in equation 1 with T=200 K and r=8.31J/mol

V=√(19/3)(8.31x300)/68/3 x 10⁻³)

=400.9m/s

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