# The ratio between the rms Speed of $H_2$ at 50K and that of $O_2$ at 800K is :

$(a)\;4\qquad(b)\;2\qquad(c)\;1\qquad(d)\;\large\frac{1}{4}$

Since $\large\frac{u_1}{u_2} = \sqrt{\large\frac{3RT_1}{M_1}\times\large\frac{M_2}{3RT_2}}$
$\therefore \sqrt{\large\frac{T_1M_2}{T_2M_1}} = \sqrt{\large\frac{50\times32}{800\times2}}$
= 1