Answer;
414.0 m/s
Explanation;
From kinetic theory for an ideal gas ..
Mean KE of a particle; ½mv² = 3kT/2
For 1 mol of particles (L); Total KE = L½mv² = 3RT/2
(Lm)½v² = 3RT/2
Lm = molar mass 0.0399kg, R= molar gas constant 8.30 J/(K.mol),
T = Kelvin temp 275K
v² = 3RT / Lm
v² = 3 x 8.30 x 275 / 0.0399
= 1.716^5
v(rms) = √1.716^5
v(rms) = 414.0 m/s