At what temperature is the root mean square speed of an atom in an argon gas cylinder equal to the rms speed of a helium gas atom at \(-20^\circ \mathrm{C}?\)
(Given the atomic mass of \(\text{Ar}=39.9~\text{u}\) and of \(\text{He}=4.0~\text{u}\)).
1. \(1.01 \times 10^3 ~\text{K} \)
2. \(3.15 \times 10^3 ~\text{K} \)
3. \(1.91 \times 10^3~ \text{K} \)
4. \(2.52 \times 10^3 ~\mathrm{K}\)

From a certain apparatus, the diffusion rate of hydrogen has an average value of 28.7 $c{m}^3 s^{-1}$. The diffusion of another gas under the same conditions is measured to have an average rate of 7.2 $c{m}^3 s^{-1}$. The unknown gas is:
1. Oxygen
2. Nitrogen
3. Helium
4. None of these