What is the ratio of r.m.s speed of Oxygen and Hydrogen molecules at the same temperature?

An oxygen cylinder of volume $30$ litres has an initial gauge pressure of $15 \mathrm{atm}$ and a temperature of $27 °\mathrm{C}$. After some oxygen is withdrawn from the cylinder, the gauge pressure drops to $11 \mathrm{atm}$ and its temperature drops to $17 °\mathrm{C}$. Estimate the mass of oxygen taken out of the cylinder ( $\mathrm{R}=8.31 {\mathrm{Jmol}}^{–1}{\mathrm{K}}^{–1}$, molecular mass of ${\mathrm{O}}_2=32 \mathrm{u}$).

Estimate the average thermal energy of a helium atom at (i) room temperature ($27 °\mathrm{C}$), (ii) the temperature on the surface of the Sun ($6000 \mathrm{K}$), (iii) the temperature of $10$million Kelvin (the typical core temperature in the case of a star).

Estimate the mean free path and collision frequency of a nitrogen molecule in a cylinder containing nitrogen at $2.0 \mathrm{atm}$ and temperature $17 °\mathrm{C}$. Take the radius of a nitrogen molecule to be roughly $1.0 {\mathrm{A}}^{°}$. Compare the collision time with the time the molecule moves freely between two successive collisions (Molecular mass of ${\mathrm{N}}_2 = 28.0 \mathrm{u}$).