Question

Five moles of helium is mixed with two moles of hydrogen to form a mixture. Take molar mass of helium $M_1=4g$ and that of hydrogen $M_2=2g$.
The equivalent value of $\gamma$ is:

• A. 1.59
• B. 1.53
• C. 1.56
• D. None of the above

Answer 1

The correct option is A 1.59

Mole fraction of $He=\frac{5}{7}=0.714$
Mole fraction of $H_2=\frac{2}{7}=0.285$
The Poissin's ratio $\gamma$ for $He$ and $H_2$ are 1.659 and 1.412 respectively.
The Poissin's ratio $\gamma$ for the mixture is $1.659\times 0.714+1.412\times 0.285=1.185+0.40=1.59$