The root mean square of the particles in a gas is given by
[tex]v_{rms} = \sqrt{ \frac{3RT}{M_m} }[/tex]
where
R is the gas constant
T is the absolute temperature of the gas
Mm is the molar mass of the gas
For the argon gas in our problem, the temperature is T=2000 K while the molar mass of argon is [tex]M_m = 0.040 kg/mol[/tex], so we can find the rms speed of the gas by using the previous formula:
[tex]v_{rms} = \sqrt{ \frac{3 \cdot 8.31 J mol^{-1} K^{-1} \cdot 2000 K}{0.040 kg/mol} }=1116.5 m/s [/tex]
