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 \(-20^\circ \text{C}?\)
(Given the atomic mass of \(\mathrm{Ar}=39.9~\text{u}\) and of \(\mathrm{He}=4.0~\text{u}\))
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. \(2.52 \times 10^3 ~\text{K}\)

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