At a given temperature,which gas will have a higher speed between $H_2$ and $O_2$? Why?

(A) The speed of $H_2$ gas will be higher because gases with lower molecular mass have higher speeds. According to Graham's law of diffusion,the rate of diffusion $r$ is inversely proportional to the square root of the molar mass $M$,i.e.,$r \propto \frac{1}{\sqrt{M}}$. Since the molar mass of $H_2$ $(2 \ g/mol)$ is less than that of $O_2$ $(32 \ g/mol)$,$H_2$ will have a higher speed.