Helium gas is stored at 293 K and 500 kPa in a 1-cm thick, 2-m-inner-diameter spherical tank made of fused silica (SiO2)

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Helium gas is stored at 293 K and 500 kPa in a 1-cm thick,
2-m-inner-diameter spherical tank made of fused silica (SiO2). The
area where the container is located is well ventilated. The
solubility of helium in fused silica (SiO2) at 293 K and 500 kPa is
0.00045 kmol/m3.bar. The diffusivity of helium in fused silica at
293 K is 4×10-14 m2/s. Determine: a) The mass transfer resistance
of helium b) Mass transfer rate of helium in kmol/s by diffusion
through the tank. c) The mass flow rate of helium in kg/s by
diffusion through the tank