Question

The lunar surface reaches 370 K by midday. The atmosphere consists of neon, argon and traces of helium at a total pressure of only 2 x 10-14 atm. Calculate the root mean square speed of each component in the lunar atmosphere

Answer 1

T = 370 K

Mr_Ne = 20.18 g/mol = 0.02018 kg/mol

Mr_Ar = 39.95 g/mol = 0.03995 kg/mol

Mr_He = 4 g/mol = 0.004 kg/mol

R = 8.314

Vrms = $\sqrt{\frac{3RT}{M}}$

Vrms_Ne = $\sqrt{\frac{3\times 8.314\times370}{0.02018}}$ = 676.24 m/s

Vrms_Ar = $\sqrt{\frac{3\times 8.314\times370}{0.03995}}$ = 480.63 m/s

Vrms_He = $\sqrt{\frac{3\times 8.314\times370}{0.004}}$ = 1518.93 m/s