Question

Which of the following gases has the highest value of $rms$ velocity at $298\, K$?

• A. $CH_4$
• B. $CO$
• C. $Cl_2$
• D. $CO_2$

Answer 1

Answer: (A)

$CH_4$

Answer 2

RMS-velocity of a gas $v_{\text {rms }}=\sqrt{\frac{3 R T}{M}}$

Hence, higher the molecular weigth of a gas, lower will be its RMS-velocity

$v_{ rms } \propto \sqrt{\frac{1}{M}}$
$\therefore CH _{4}( mol$. weight $=16 )$ has highest RMS-velocity.