Question

A latex balloon, wall thickness 3.091 x 10-4 m, contains helium at a concentration of 0.72 kg m-3. Under these conditions the total surface area of the balloon is 0.17 m2. The diffusion coefficient of He in latex at room temperature is 4.9 x 10-9 m2s-1. Calculate the rate of helium effusion (in g/hr) from the balloon.

Answer 1

He loss rate (kg/s)
= (area)*(He density)*(D/t)

D is the diffusion coefficient
t is the wall thickness in meters

= (0.17)*(0.72)*(4.9*10^-9)/3.09*10^-4
= 1.94*10^-6 kg/sec
= 1.94*10^-3 g/s = 7.0 g/hr

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