Question

Velocity of sound is maximum in

• A. $He$
• B. $N_2$
• C. $H_2$
• D. $O_2$

Answer 1

Answer: (C)

$H_2$

Velocity of sound in a gas medium $v=\sqrt{\frac{\gamma RT}{M}}$
$⟹$ $v=k\sqrt{\frac{\gamma }{M}}$
where $k=$ constant
For monoatomic gas : $\gamma =1.67$
For diatomic gas : $\gamma =1.4$
So, $v_{He}=k\sqrt{\frac{1.67}{4}}=k\sqrt{0.42}$
$v_{N_2}=k\sqrt{\frac{1.4}{28}}=k\sqrt{0.05}$
$v_{H_2}=k\sqrt{\frac{1.4}{2}}=k\sqrt{0.7}$
$v_{O_2}=k\sqrt{\frac{1.4}{32}}=k\sqrt{0.044}$
Thus velocity of sound is maximum in $H_2$.