What is the rms speed of the argon atoms?

Question

A gas consists of a mixture of neon and argon. The rms speed of the neon atoms is 450 m/s.

What is the rms speed of the argon atoms in m/s?

Answer 1

The average atomic mass of neon is 20.1797, while the average atomic mass of argon is 39.948.  Both are monatomic noble gases.  With that said, the mixture at equilibrium would be at a uniform temperature.  Temperature is a measure of the average kinetic energy of a group of atoms.  So I would make the assumption that each atom of neon on average has the same kinetic energy as an atom of argon.  Using this...

0.5 m v^2 (neon) = 0.5 M V^2 (argon)

Solving for V (speed of argon)...

V = v √(m/M) = 450 √(20.1797/39.948) m/s

V = 319.8 m/s or rounded to 320 m/s

Hope this helps.