Question 1: The mean speed for escaping molecules from a hole is 1.88*(k*T)/m)^1/2 (Eq.1) The mean speed for molecules in the Maxwell-Boltz Distribution is 1.596*((k*T)/m)^1/2 (Eq.2 If you were to calculate molecular flux for an ideal gas, which expression would you use? In my textbook, it uses Eq.2 This does not make sense to me. I would use Eq.1 Question 2: How does I*dv = 1/4*v*n*dv (Eq.3), using I=1/4*n*vmean (Eq.4)? Eq.3 represents molecular flux, I (that strike a surface, per unit area and per unit time) with molecular speeds in the range v+dv Eq.4 represents molecular flux, I I understand the derivation for Eq.4 I do not understand how can you use Eq.4, which has vmean, to get to Eq.3, which has v? Any help would be appreciated!