Problem
posted by asd .
A latex balloon, wall thickness 3.091 x 104 m, contains helium at a concentration of 0.92 kg m3. Under these conditions the total surface area of the balloon is 0.26 m2. The diffusion coefficient of He in latex at room temperature is 4.9 x 109 m2s1. Calculate the rate of helium effusion (in g/hr) from the balloon.

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Fick’s Law
M= D•(Δρ/Δx)•A,
where
M = m/t = mass flux [kg/s],
D= 4.9•10 ⁻⁹ m ²/s is the diffusion coefficient (diffusivity) [m²/s],
Δρ/Δx is the gradient of density [kg/m⁴],
A is the area [m²].
M=  4.9•10⁻⁹•(0  0.35)/3.091•10⁻⁴)•0.88 =
4.9•10⁻⁹•0.35•0.88/3.091•10⁻⁴=
=4.88•10⁻⁶ kg/s= 17.58 g/hr